Apache2 errorlog x-forwarded-for

apache2 errorlog x-forwarded-for

Open your Apache configuration file using a text editor. In the LogFormat section, add %{X-Forwarded-For}i, similar to the following: Save your. In order to log the source IP from the X-Forwarded-For header on the app server, we will want to edit the Apache configuration file on your application. As user's request traverses out of their network, the X-Forwarded-For (XFF) header is appended with IP address of each successive proxy. For.

Apache2 errorlog x-forwarded-for - alone!

Apache and X-Forwarded-For Header (XFF)

It's easier to get Apache to log client IP addresses utilizing X-Forwarded-For Headers than it is using IIS. By default, the logs do not record source IP addresses for clients - but as of Apache version 2.4 you can use the ErrorLogFormat directive in the httpd.conf file as explained below.

->Did you want to learn about XFF on IIS?

There’s been a lot of debate here in the office about how best to capture both your Loadbalancer’s IP and the Source IP of the user in your access_log in Apache 2.4. This is the tried and tested method we've come up with.

Related blog: NGINX and X-Forwarded-For-Header

CentOS 7

When you start out, your httpd.conf will look something like this:

Now the %h is already there to capture your header, which, by default, will capture the IP of the Loadbalancer (the last proxy server that the traffic came from). All of these entries need to commented out.

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Assuming you have X-Forwarded-For enabled in the load balancer (or whatever proxy server you're using), you can capture the source IP from the original client. You'll need to change your config file entries to look like this:

After making this change, restart the httpd service:

If you review the logs on the web server now, you'll see the client source address, which has been passed through using the X-Forward-For Header:


Debian/Ubuntu

Directives should be added to the specific site configuration file, /etc/apache2/sites-available/000-default.conf.

You will also need to enable the following modules:

Next, add the logging directives into the site specific configuration file:

After making these changes, restart the apache2 service:

If you have any questions or experience any issues, email [email protected] and the team will be happy to help.

apache_feather

The standard LogFormat directive:

To add the client's source IP address, just change this to:

To add the client's source IP address and put quotes around each field (useful when importing the logs into a spreadsheet or database):

Once you’ve made the change, restart Apache and you’re done. The examples below show the resulting log entries for each configuration.

Standard logs:

Client IPs added:

Client IPs added and all fields encapsulated in quotes:

Note:

  • 192.168.2.210 is the IP of the Ethernet interface (eth0) on the load balancer
  • 192.168.2.7 is the IP of my test PC

One other point. If you also have Pound SSL in your configuration, once you’ve added the X-Forwarded-For bit to your LogFormat directive, the logs will also record an additional entry for the Pound virtual server as shown below:

The additional IP address (192.168.2.212) in this example  is the IP of the Pound Virtual Server.

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IIS and X-Forwarded-For-Header

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Apache Module mod_log_config

Summary

This module provides for flexible logging of client requests. Logs are written in a customizable format, and may be written directly to a file, or to an external program. Conditional logging is provided so that individual requests may be included or excluded from the logs based on characteristics of the request.

Three directives are provided by this module: to create a log file, to set a custom format, and to define a log file and format in one step. The and directives can be used multiple times in each server to cause each request to be logged to multiple files.

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Topics

Directives

Bugfix checklist

See also

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Custom Log Formats

The format argument to the and directives is a string. This string is used to log each request to the log file. It can contain literal characters copied into the log files and the C-style control characters "\n" and "\t" to represent new-lines and tabs. Literal quotes and backslashes should be escaped with backslashes.

The characteristics of the request itself are logged by placing "" directives in the format string, which are replaced in the log file by the values as follows:

The percent sign.
Client IP address of the request (see the module).
Underlying peer IP address of the connection (see the module).
Local IP-address.
Size of response in bytes, excluding HTTP headers.
Size of response in bytes, excluding HTTP headers. In CLF format, i.e. a '' rather than a 0 when no bytes are sent.
The contents of cookie in the request sent to the server. Only version 0 cookies are fully supported.
The time taken to serve the request, in microseconds.
The contents of the environment variable .
Filename.
Remote hostname. Will log the IP address if is set to , which is the default. If it logs the hostname for only a few hosts, you probably have access control directives mentioning them by name. See the Require host documentation.
Like , but always reports on the hostname of the underlying TCP connection and not any modifications to the remote hostname by modules like .
The request protocol.
The contents of header line(s) in the request sent to the server. Changes made by other modules (e.g. ) affect this. If you're interested in what the request header was prior to when most modules would have modified it, use to copy the header into an internal environment variable and log that value with the described above.
Number of keepalive requests handled on this connection. Interesting if is being used, so that, for example, a '1' means the first keepalive request after the initial one, '2' the second, etc...; otherwise this is always 0 (indicating the initial request).
Remote logname (from identd, if supplied). This will return a dash unless is present and is set .
The request log ID from the error log (or '-' if nothing has been logged to the error log for this request). Look for the matching error log line to see what request caused what error.
The request method.
The contents of note from another module.
The contents of header line(s) in the reply.
The canonical port of the server serving the request.
The canonical port of the server serving the request, or the server's actual port, or the client's actual port. Valid formats are , , or .
The process ID of the child that serviced the request.
The process ID or thread ID of the child that serviced the request. Valid formats are , , and .
The query string (prepended with a if a query string exists, otherwise an empty string).
First line of request.
The handler generating the response (if any).
Status. For requests that have been internally redirected, this is the status of the original request. Use for the final status.
Time the request was received, in the format . The last number indicates the timezone offset from GMT
The time, in the form given by format, which should be in an extended format (potentially localized). If the format starts with (default) the time is taken at the beginning of the request processing. If it starts with it is the time when the log entry gets written, close to the end of the request processing. In addition to the formats supported by , the following format tokens are supported:
number of seconds since the Epoch
number of milliseconds since the Epoch
number of microseconds since the Epoch
millisecond fraction
microsecond fraction
These tokens can not be combined with each other or formatting in the same format string. You can use multiple tokens instead.
The time taken to serve the request, in seconds.
The time taken to serve the request, in a time unit given by . Valid units are for milliseconds, for microseconds, and for seconds. Using gives the same result as without any format; using gives the same result as . Combining with a unit is available in 2.4.13 and later.
Remote user if the request was authenticated. May be bogus if return status () is 401 (unauthorized).
The URL path requested, not including any query string.
The canonical of the server serving the request.
The server name according to the setting.
Connection status when response is completed:
=Connection aborted before the response completed.
=Connection may be kept alive after the response is sent.
= Connection will be closed after the response is sent.
Bytes received, including request and headers. Cannot be zero. You need to enable to use this.
Bytes sent, including headers. May be zero in rare cases such as when a request is aborted before a response is sent. You need to enable to use this.
Bytes transferred (received and sent), including request and headers, cannot be zero. This is the combination of %I and %O. You need to enable to use this.
The contents of trailer line(s) in the request sent to the server.
The contents of trailer line(s) in the response sent from the server.

Modifiers

Particular items can be restricted to print only for responses with specific HTTP status codes by placing a comma-separated list of status codes immediately following the "%". The status code list may be preceded by a "" to indicate negation.

Logs on 400 errors and 501 errors only. For other status codes, the literal string will be logged.
Logs on all requests that do not return one of the three specified codes, "" otherwise.

The modifiers "<" and ">" can be used for requests that have been internally redirected to choose whether the original or final (respectively) request should be consulted. By default, the directives and look at the original request while all others look at the final request. So for example, can be used to record the final status of the request and can be used to record the original authenticated user on a request that is internally redirected to an unauthenticated resource.

Format Notes

For security reasons, starting with version 2.0.46, non-printable and other special characters in , and are escaped using sequences, where stands for the hexadecimal representation of the raw byte. Exceptions from this rule are and , which are escaped by prepending a backslash, and all whitespace characters, which are written in their C-style notation (, , etc). In versions prior to 2.0.46, no escaping was performed on these strings so you had to be quite careful when dealing with raw log files.

Since httpd 2.0, unlike 1.3, the and format strings do not represent the number of bytes sent to the client, but simply the size in bytes of the HTTP response (which will differ, for instance, if the connection is aborted, or if SSL is used). The format provided by will log the actual number of bytes sent over the network.

Note: is implemented as a quick-handler and not as a standard handler. Therefore, the format string will not return any handler information when content caching is involved.

Examples

Some commonly used log format strings are:

Common Log Format (CLF)
Common Log Format with Virtual Host
NCSA extended/combined log format
Referer log format
Agent (Browser) log format

You can use the directive multiple times to build up a time format using the extended format tokens like :

Timestamp including milliseconds
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Security Considerations

See the security tips document for details on why your security could be compromised if the directory where logfiles are stored is writable by anyone other than the user that starts the server.

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BufferedLogsDirective

The directive causes to store several log entries in memory and write them together to disk, rather than writing them after each request. On some systems, this may result in more efficient disk access and hence higher performance. It may be set only once for the entire server; it cannot be configured per virtual-host.

This directive should be used with caution as a crash might cause loss of logging data.

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CustomLogDirective

Description:Sets filename and format of log file
Syntax:
Context:server config, virtual host
Status:Base
Module:mod_log_config

The directive is used to log requests to the server. A log format is specified, and the logging can optionally be made conditional on request characteristics using environment variables.

The first argument, which specifies the location to which the logs will be written, can take one of the following two types of values:

A filename, relative to the .
The pipe character "", followed by the path to a program to receive the log information on its standard input. See the notes on piped logs for more information.

Security:

If a program is used, then it will be run as the user who started . This will be root if the server was started by root; be sure that the program is secure.

Note

When entering a file path on non-Unix platforms, care should be taken to make sure that only forward slashed are used even though the platform may allow the use of back slashes. In general it is a good idea to always use forward slashes throughout the configuration files.

The second argument specifies what will be written to the log file. It can specify either a defined by a previous directive, or it can be an explicit string as described in the log formats section.

For example, the following two sets of directives have exactly the same effect:

# CustomLog with format nickname LogFormat "%h %l %u %t \"%r\" %>s %b" common CustomLog "logs/access_log" common # CustomLog with explicit format string CustomLog "logs/access_log" "%h %l %u %t \"%r\" %>s %b"

The third argument is optional and controls whether or not to log a particular request. The condition can be the presence or absence (in the case of a '' clause) of a particular variable in the server environment. Alternatively, the condition can be expressed as arbitrary boolean expression. If the condition is not satisfied, the request will not be logged. References to HTTP headers in the expression will not cause the header names to be added to the Vary header.

Environment variables can be set on a per-request basis using the and/or modules. For example, if you want to record requests for all GIF images on your server in a separate logfile but not in your main log, you can use:

SetEnvIf Request_URI \.gif$ gif-image CustomLog "gif-requests.log" common env=gif-image CustomLog "nongif-requests.log" common env=!gif-image

Or, to reproduce the behavior of the old RefererIgnore directive, you might use the following:

SetEnvIf Referer example\.com localreferer CustomLog "referer.log" referer env=!localreferer
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GlobalLogDirective

The directive defines a log shared by the main server configuration and all defined virtual hosts.

The directive is identical to the directive, apart from the following differences:

  • is not valid in virtual host context.
  • is used by virtual hosts that define their own , unlike a globally specified .
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LogFormatDirective

This directive specifies the format of the access log file.

The directive can take one of two forms. In the first form, where only one argument is specified, this directive sets the log format which will be used by logs specified in subsequent directives. The single argument can specify an explicit as discussed in the custom log formats section above. Alternatively, it can use a to refer to a log format defined in a previous directive as described below.

The second form of the directive associates an explicit with a . This can then be used in subsequent or directives rather than repeating the entire format string. A directive that defines a nickname does nothing else -- that is, it only defines the nickname, it doesn't actually apply the format and make it the default. Therefore, it will not affect subsequent directives. In addition, cannot use one nickname to define another nickname. Note that the nickname should not contain percent signs ().

Example

LogFormat "%v %h %l %u %t \"%r\" %>s %b" vhost_common
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TransferLogDirective

This directive has exactly the same arguments and effect as the directive, with the exception that it does not allow the log format to be specified explicitly or for conditional logging of requests. Instead, the log format is determined by the most recently specified directive which does not define a nickname. Common Log Format is used if no other format has been specified.

Example

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" TransferLog logs/access_log
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Comments

Notice:
This is not a Q&A section. Comments placed here should be pointed towards suggestions on improving the documentation or server, and may be removed by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Libera.chat, or sent to our mailing lists.

Nextcloud community

@kesselb - first of all, thanks a lot for following up, I am quite lost in the settings to be frank.

kesselb:

Tell caddy to send the forward to as x-real-ip and you are good

I set this on caddy and these are the headers which are forwarded to each container (including nextcloud). I removed the non-X ones:

So is there, it is the IP of the client calling nextcloud.

I also set in the docker-compose file for nextcloud (this is the internal docker network, on which all containers are, including the reverse proxy)

I tried to set and unset (again, in the docker-compose file for nextcloud) .

None of this changed the logging, this is still the IP of the proxy that is displayed.

I then recalled that you wrote (emphasis mine)

Or enable remoteip again and tell caddy to send x-forwarded-for as x-real-ip. But overwritehost and overwriteprotcol are mandatory then.

I am not sure what they mean - the documentation says that these “set the protocol and hostname of the proxy”. I do not know what “the hostname of the proxy” is supposed to be.

My proxy (caddy) has a CNAME (and many others, one for each service behind the proxy). I tried to set this as (and as because the full URI is - but this did not change anything.

All this was done with a clean nextcloud configuration, the only things I changed there are

(the actual domain name is mine of course)

Maybe the refers to the IP the call comes from (the IP of the proxy, as seen within nextcloud network), so I tried

Same thing: the IP of the proxy is logged

Here at VG we have loadbalancers and proxies in front of most of our webservers.
This is key to being able to handle the big amounts of traffic we get.

One problem that arise when traffic is being terminated this way is that the backend webserver, namely Apache will get either the IP of the loadbalancer or the proxy as originating address.

This is of course not desirable since we cannot see the actual client IP in the logs, and thus we cannot make other rules based on client IP in Apache.


What do we want?

  • Use the rightmost unknown IP of the X-Forwarded-For header, since this will contain the actual client IP.
  • Be able to define a subnet which are not rewritten.
  • Return the actual client ip in web applications.
  • Log the correct IP both in the error log and access log.
  • The solution should work with deny/allow, mod_rewrite, etc.

The solution

The solution is to make the loadbalancer and proxies set an extra header in the request to the backend server containing the actual client IP.
This header could be called whatever you’d like, but the most conventionally used name is X-Forwarded-For.

But how do we tell Apache to rewrite client IP and use the IP specified in the header ?

In Apache 2.4 there is included a module called mod_remoteip which does exactly this, but what if you use Apache 2.2 ?
Well, there exists a backport of mod_remoteip which is compatible with Apache 2.2.

However, this module does not suit our needs since it seems to break with mod_rewrite.
Then we have mod_rpaf, mod_extract_forwarded which also fail to do exactly what we want.

mod_vgremoteip

After testing out a bunch of different modules and observing that none of them fit all our requirements I ended up writing my own module based on mod_remoteip.

This have been tested thoroughly for a couple of months and seems to do the job well.

If you are interested in testing it out the source and build instructions are available on GitHub, https://github.com/vgnett/mod_vgremoteip

Example configuration:

[code language="apache"]

LoadModule vgremoteip_module modules/mod_vgremoteip.so

 

&lt;IfModule mod_vgremoteip.c&gt;

# Name of header which contains the 'real' client IP†.

VGRemoteIPHeaderX-Forwarded-For

 

# Subnet to mark as trusted subnet (this ip will be allowed to set the X-Forwarded-For header and marked as a proxy ip).

# You should specify this.

VGTrustedProxy10.1.0.0/26

 

# You can also specify a single ip addresses.

# Do not specify hostnames.

VGTrustedProxy127.0.0.1

&lt;/IfModule&gt;

[/code]

A little note on security

If you choose to make access restrictions based on the IP in X-Forwarded-For header you must ensure that the configuration do not in any way allow the client to tamper with the header.

Background

By default, our Load Balancer servertemplates will forward the 'X-Forwarded-For' HTTP header, which contains the source client IP address of the request, through to your backend application server. This IP address isn't logged anywhere by default though, so this article explains how we can add this header to the Apache access logs on the backend (application) servers in order to see where the request originated from.

Answer

In order to log the source IP from the X-Forwarded-For header on the app server, we will want to edit the Apache configuration file on your application server. This is normally located in:

Ubuntu: /etc/apache2/apache2.conf

Centos: /etc/httpd/conf/httpd.conf

Edit the file with a text editor and locate the 'LogFormat' lines, which defines how our access and error logs should output their content. By default, we will be looking at the 'combined' LogFormat line, but you can add this to any LogFormat line you wish. It will look similar to this:

To add in the X-Forwarded-For, we will simply use the variable and integrate it into the LogFormat line, so you will want to change this line like so:

Save the change to the Apache config file, then restart/reload Apache. After a restart, view your access.log files, and you should notice that the source IP now being logged. Access logs are normally located in /var/log/apache2/ or /var/log/httpd/ (depending on distribution), though they may be elsewhere depending on templates used or app configuration.

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How to View and Configure Apache Access & Error Logs

At the time of writing, the Apache HTTP server is used by 30.8% of all web servers in operation. If you're responsible for managing any system that utilizes Apache, then you will surely interact with its logging infrastructure on a regular basis. This tutorial will introduce you to logging in Apache and how it can help you diagnose, troubleshoot, and quickly resolve any problem you may encounter on your server.

You will learn where logs are stored, how to access them, and how to customize the log output and location to fit your needs. You will also learn how to centralize Apache logs in a log management system for easier tracing, searching, and filtering of logs across your entire stack.

Here's an outline of what you will learn by following through with this tutorial:

  • Where Apache logs are stored and how to access them.
  • How to customize the Apache log format and storage location to fit your needs.
  • How to utilize a structured format (such as JSON) for your Apache logs.
  • How to centralize Apache logs in a log management system.

Prerequisites

To follow through with this tutorial, you should set up a Linux server that includes a non-root user with privileges. Additionally, you also need the Apache HTTP server installed and enabled on the server, which can be done by executing the relevant commands below.

On Debian-based distributions like Ubuntu:

On RHEL, Fedora or CentOS:

Please note that the rest of the commands, directory configurations, and conventions used in this tutorial pertain to Debian-based distributions like Ubuntu. Still, the concepts remain the same for other distributions.

Step 1 — Getting started with Apache logging

Apache logs are files that record everything the Apache web server is doing for later analysis by the server administrator. The records of all Apache events are placed in two different text files:

  • Access Log: this file stores information about incoming requests. You'll find details about each request such as the requested resource, response codes, time taken to generate the response, IP address of the client, and more.
  • Error Log: this file contains diagnostic information about any errors were encountered while processing requests.

Step 2 — Locating the Apache log files

The log files' location depends on the operating system the Apache web server is running. On Debian-based operating systems like Ubuntu, the access log file is located in . On CentOS, RHEL, or Fedora, the access log file is stored in .

A typical access log entry might look like this:

Output

Similarly, the error log file is located in on Debian-based systems and on CentOS, RHEL, or Fedora. A typical error log entry might look like this:

Output

In the next section, we'll discuss how to view these log files from the command line.

Step 3 — Viewing Apache Log files

One of the most common ways to view an Apache log file is through the command which prints the last 10 lines from a file. When the option is supplied, the command will watch the file and output its contents in real-time.

You should observe the following output on the screen:

Output

To view the entire contents of the file, you can use the command or open the file in a text editor like or :

You may also want to filter the log entries in the log file by a specific term. In such cases, you should use the command. The first argument to is the term you want to search for, while the second is the log file that will be searched. In example below, we are filtering all the lines that contain the word :

This should present the following output:

Output

Step 4 — Examining Apache access log formats

The access log records all requests that are processed by the server. You can see what resources are being requested, the status of each request, and how long it took to process their response. In this section, we'll dive deeper into how to customize the information that is displayed in this file.

Before you can derive value from reading a log file, you need to understand the format that is being used for each of its entries. The directive is what controls the location and format of the Apache access log file. This directive can be placed in the server configuration file () or in your virtual host entry. Note that defining the same directive in both files may cause problems.

Let's look at the common formats used in Apache access logs and what they mean.

Common Log Format

The Common Log Format is the standardized access log format format used by many web servers because it is easy to read and understand. It is defined in the configuration file through the directive.

When you run the command below:

You will observe the following output:

Output

The line above defines the nickname and associates it with a particular log format string. A log entry produced by this format will look like this:

Output

Here's an explanation of the information contained in the log message above:

  • -> : the hostname or IP address of the client that made the request.
  • -> : remote log name (name used to log in a user). A placeholder value () will be used if it is not set.
  • -> : remote username (username of logged-in user). A placeholder value () will be used if it is not set.
  • -> : the day and time of the request.
  • -> - the request method, route, and protocol.
  • -> - the response code.
  • -> - the size of the response in bytes.

Combined Log Format

The Combined Log Format is very similar to the Common log format but contains few extra pieces of information.

It's also defined in the configuration file:

You will observe the following output:

Output

Notice that it is exactly the same as the Common Log Format, with the addition of two extra fields. Entries produced in this format will look like this:

Output

Here's an explanation of the two additional fields that are not present in the Common log format:

  • -> : the URL of the referrer (if available, otherwise is used).
  • -> : detailed information about the user agent of the client that made the request.

Step 5 — Creating a custom log format

You can define a custom log format in the file by using the directive followed by the actual format of the output and a nickname that will be used as an identifier for the format. After defining the custom format, you'll pass its nickname to the directive and restart the service.

In this example, we will create a log format named that looks like this:

Output

Open your file and place the line above below the other lines. It will produce access log entries with the following details:

  • : date and time of the request.
  • : the request protocol.
  • : the request method.
  • : the URL path requested.
  • : query parameters (if any).
  • : total bytes received including the request headers.
  • : final HTTP status code.
  • : number of bytes sent in the response.
  • : time taken to generate the response in milliseconds.

You can find all other formatting options and their description on this page.

To enable the custom format for subsequent access log entries, you must change the value of the directive in your virtual hosts file and restart the service with Systemctl.

Open up the default virtual hosts file using the command below:

Find the following line:

Output

And change it to:

Output

Save the file by pressing then , then restart the service using the command below:

Afterward, make the following request to your server using :

You should observe the following response:

Output

Go ahead and view the last 10 messages in the access log file:

The log entry that describes the request will look like this:

Output

It's also possible to create multiple access log files by specifying the directive more than once. In the example below, the first line logs into a file using the log format, while the second uses the format to write entries into . Similarly, the file contains messages formatted according to the log format.

Output

Step 6 - Formatting your logs as JSON

Although many log management systems support the default Apache logging formats, it might be best to log in a structured format like JSON since that's the go-to format for structured logging in the industry and it is universally supported. Here's a conversion of our log format into JSON:

Output

This produces log entries with the following formatting:

Output

Step 7 — Configuring Apache error logs

The server error log contains information about any errors that the web server encountered while processing incoming requests as well as other diagnostic information. You can choose where the error messages will be transported to using the directive in your virtual host configuration file. This transport is usually a log file on the filesystem.

Here is an example from default virtual host configuration file :

Output

On Debian-based distributions, the default error log is in the file, while in Fedora/CentOS/RHEL, it placed in the file. If the path argument to is not absolute, then it is assumed to be relative to the ServerRoot.

A common practice is to monitor the error log continuously for any problems during development or testing. This is easily achieved through the command:

You will observe the following output:

Output

Aside from logging directly to a file, you can also forward your logs to a Syslog. You can do this by specifying instead of a file path as the argument to :

Step 8 — Customizing the error log format

Like the Apache access logs, the format of the error messages can be controlled through the directive, which should be placed in the main config file or virtual host entry. It looks like this:

Output

The above configuration produces a log entry in the following format:

Output

Here's an explanation of the formatting options used above:

: the current time, including microseconds. : the log level of the message. : the process identifier. : the thread identifier. : the client IP address. : the actual log message.

Note that when the data for a formatting option is not available in a particular event, it will be omitted from the log entirely as the Apache error log doesn't use placeholder values for missing parameters.

You can find a complete description of all the available error formatting options in the Apache docs.

Step 9 — Customizing the error log level

In the virtual host configuration file, you can also control the level of messages that will be entered into the error log through the LogLevel directive. When you specify a particular value, messages from all other levels of higher severity will be logged as well. For example, when is specified, messages with a severity of , , and will also be logged.

These are the levels available in increasing order of severity:

  • - : trace messages (lowest severity).
  • : messages used for debugging.
  • : informational messages.
  • : normal but significant conditions.
  • : warnings.
  • : error conditions that doesn't necessarily require immediate action.
  • : critical conditions that requires prompt action.
  • : errors that require immediate action.
  • : system is unusable.

If the directive is not set, the server will set the log level to by default.

Step 10 — Centralizing your Apache logs

Storing your Apache logs on the filesystem may suffice for development environments or single-server deployments, but when multiple servers are involved, it may be more convenient to centralize all your logs in a single location so that you can automatically parse, filter, and search log data from all sources in real-time.

In this section, we'll demonstrate how you can centralize your Apache logs in a log management service through Vector, a high-performance tool for building observability pipelines. The following instructions assume that you've signed up for a free Logtail account and retrieved your source token.

Go ahead and follow the relevant installation instructions for Vector for your operating system. On Ubuntu, you may run the following commands to install the Vector CLI:

After Vector is installed, confirm that it is up and running through :

You should observe that it is active and running:

Output

Otherwise, go ahead and start it with the command below.

Afterwards, change into a root shell and append your Logtail vector configuration for Apache into the file using the command below. Don't forget to replace the placeholder below with your source token.

Then restart the service:

You will observe that your Apache logs will start coming through in Logtail:

Streaming Apache logs to logtail

Conclusion

In this tutorial, you learned about the different types of logs that the Apache web server stores, where you can find those logs, and how to view their contents. We also discussed Apache access and error log formatting and how to create your custom log formats, including a structured JSON format. Finally, we considered how you can manage all your Apache logs in one place by using the Vector CLI to stream each entry to a log management service.

Don't forget to read the docs to find out more about all the logging features that Apache has to offer. Thanks for reading!

Logs tell stories.
Read them.

Experience SQL-compatible
structured log management.

Explore logging →

Centralize all your logs into one place.

Analyze, correlate and filter logs with SQL.

Create actionable
dashboards with Grafana.

Share and comment with built-in collaboration.

Start logging

Got an article suggestion? Let us know

Share on TwitterShare on FacebookShare via e-mail

Next article

How to View and Configure NGINX Access & Error Logs

Learn how to view and configure nginx access and error logs

Licensed under CC-BY-NC-SA

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Opinion, actual: Apache2 errorlog x-forwarded-for

TRY IF YOU HAVE HAL.DLL ERROR
ERROR CLAIMING USB INTERFACE N900
SYSTEM ERROR CODE 1060
Apache2 errorlog x-forwarded-for
Disc error occurred during write operation
apache2 errorlog x-forwarded-for

Nextcloud community

@kesselb - first of all, thanks a lot for following up, I am quite lost in the settings to be frank.

kesselb:

Tell caddy to send the forward to apache2 errorlog x-forwarded-for x-real-ip and you are good

I set this on caddy and these are the headers which are forwarded to each container (including nextcloud). I removed the non-X ones:

So is there, it is the IP of the client calling nextcloud.

I also set in the docker-compose file for nextcloud (this is the internal docker network, on which all containers are, including the reverse proxy)

I tried to set and unset (again, in the docker-compose file for nextcloud) .

None of this changed the logging, this is still the IP of the proxy that is displayed.

I then recalled that you wrote (emphasis mine)

Or enable remoteip again and tell caddy to send x-forwarded-for as x-real-ip, apache2 errorlog x-forwarded-for. But overwritehost and overwriteprotcol are mandatory then.

I am not sure what they mean - the documentation says that these “set the protocol and hostname of the proxy”. I do not know what “the hostname of the proxy” is supposed to be.

My proxy (caddy) has a CNAME (and many others, one for each service behind the proxy). I tried to set this as (and as because the full URI is - but this did not change anything.

All this was done with a clean nextcloud configuration, the only things I changed there are

(the actual domain name is mine of course)

Maybe the refers to the IP the call comes from (the IP of the proxy, as seen within nextcloud network), so I tried

Same thing: the IP of the proxy is logged

Here at VG we have loadbalancers and proxies in front of most of our webservers.
This is key to being able to handle the big amounts of traffic we get.

One problem that arise when traffic is being terminated this way is that the backend webserver, namely Apache will get either the IP of the loadbalancer or the proxy as originating address.

This is of course not desirable since we cannot see the actual client IP in the logs, and thus we cannot make other rules based on client IP in Apache.


What do we want?

  • Use the rightmost unknown IP of the X-Forwarded-For header, since this will contain the actual client IP.
  • Be able to define a subnet which are not rewritten.
  • Return the actual client ip in web applications.
  • Log the correct IP both in the error log and access log.
  • The solution should work with deny/allow, mod_rewrite, etc.

The solution

The solution is to make the loadbalancer and proxies set an extra header in the request to the backend server containing the actual client IP.
This header could be called whatever you’d like, apache2 errorlog x-forwarded-for, but the most conventionally used name is X-Forwarded-For.

But how do we tell Apache to rewrite client IP and use the IP specified in the header ?

In Apache 2.4 there is included a module called mod_remoteip which does exactly this, but what if you use Apache 2.2 ?
Well, there exists a backport of mod_remoteip which is compatible with Apache 2.2.

However, this module does not suit our needs since it seems to break with mod_rewrite.
Then we have mod_rpaf, mod_extract_forwarded which also fail to do exactly what we want.

mod_vgremoteip

After testing out a bunch of different modules and observing that none of them fit all our requirements I ended up writing apache2 errorlog x-forwarded-for own module based on mod_remoteip.

This have been tested thoroughly for a couple of months and seems to do the job well.

If you are interested in testing it out the source and build instructions are available on GitHub, https://github.com/vgnett/mod_vgremoteip

Example configuration:

[code language="apache"]

LoadModule vgremoteip_module modules/mod_vgremoteip.so

 

&lt;IfModule mod_vgremoteip.c&gt;

# Name of header which contains the 'real' client IP†.

VGRemoteIPHeaderX-Forwarded-For

 

# Subnet to mark as trusted subnet (this ip will be allowed to set the X-Forwarded-For header and marked as a proxy ip).

# You should specify this.

VGTrustedProxy10.1.0.0/26

 

# You can also specify a single ip addresses.

# Do not specify hostnames.

VGTrustedProxy127.0.0.1

&lt;/IfModule&gt;

[/code]

A little note on security

If you choose to make access restrictions based on the IP in X-Forwarded-For header you must ensure that the configuration do not in any way allow the client to tamper with the header.

How to View and Configure Apache Access & Error Logs

At the time boot error usb ubuntu writing, the Apache HTTP server is used by 30.8% of all web servers in operation. If you're responsible for managing any system that utilizes Apache, then you will surely interact with its logging infrastructure on a regular basis. This tutorial will introduce you to logging in Apache and how it can help you diagnose, troubleshoot, apache2 errorlog x-forwarded-for, and quickly resolve any problem you may encounter on your server.

You will learn where logs are stored, how to access them, apache2 errorlog x-forwarded-for, and how to customize the log output and location to fit your needs. You will also learn how to centralize Apache logs in a log management system for easier tracing, searching, apache2 errorlog x-forwarded-for filtering of logs across your entire stack.

Here's an outline of what you will learn by following through with this tutorial:

  • Where Apache logs are stored and how to access them.
  • How to customize the Apache log format and storage location to fit your needs.
  • How to utilize a structured format (such as JSON) for your Apache logs.
  • How to centralize Apache logs in a log management system.

Prerequisites

To follow through with this tutorial, you should set up apache2 errorlog x-forwarded-for Linux server that includes a non-root user with privileges, apache2 errorlog x-forwarded-for. Additionally, you also need the Apache HTTP server installed and enabled on the server, apache2 errorlog x-forwarded-for, which can be done by executing the relevant commands below.

On Apache2 errorlog x-forwarded-for distributions like Ubuntu:

On RHEL, Fedora or CentOS:

Please note that the rest of the commands, directory configurations, and conventions used in this tutorial pertain to Debian-based distributions like Ubuntu, apache2 errorlog x-forwarded-for. Still, the concepts remain the same for other distributions.

Step 1 — Getting started with Apache logging

Apache logs are files that record everything the Apache web server is doing for later analysis by the server administrator, apache2 errorlog x-forwarded-for. The records of all Apache events are placed in two different text files:

  • Access Log: this file stores information about incoming requests. You'll find details about each request such as the requested resource, response codes, time taken to generate the response, IP address of the client, and more.
  • Error Log: this file contains diagnostic information about any errors were encountered while processing requests.

Step 2 — Locating the Apache log files

The log files' location depends on the operating system the Apache web server is running. On Debian-based operating systems like Ubuntu, the access log file is located in. On CentOS, RHEL, or Fedora, apache2 errorlog x-forwarded-for, the access log file is stored in .

A typical access log entry might look like this:

Output

Similarly, the error log file is located in on Debian-based systems and on CentOS, RHEL, apache2 errorlog x-forwarded-for, or Fedora. A typical error log entry might look like this:

Output

In the next section, we'll discuss how to view these log files from the command line.

Step 3 — Viewing Apache Log files

One of the most common ways to view an Apache log file is through the command which prints the last 10 lines from a file. When the option is supplied, the command will watch the file and output its contents in real-time.

You should observe the following output on the screen:

Output

To view the entire contents of the file, you can use the command or open the file in a text editor like or :

You may also want to filter the log entries in the log file by a specific term. In such cases, you should use the command, apache2 errorlog x-forwarded-for. The first argument to is the term you want to search for, while error initializing opera module 10 second is the log file that will be searched. In example below, we are filtering all the lines that contain the word :

This should present the following output:

Output

Step 4 — Examining Apache access log formats

The access log records all requests that are processed by the server. You can see what resources are being requested, the status of each request, and how long it took to process their response. In this section, apache2 errorlog x-forwarded-for, we'll dive deeper into how to customize the information that is displayed in this file.

Before you can derive value from reading a log file, you need to understand the format that is being used for each of its entries. The directive is what controls the location and format of the Apache access log file. This directive can be placed in the server configuration file () or in your virtual host entry. Note that defining the same directive in both files may cause problems.

Let's look at the common formats used in Apache access logs and what they mean.

Common Log Format

The Common Log Format is the standardized access log format format used by many web servers because it is easy to read and understand, apache2 errorlog x-forwarded-for. It is defined openoffice runtime error the configuration file through the directive.

When you run the command below:

You will observe the following output:

Output

The line above defines the nickname and associates it with a particular log format string, apache2 errorlog x-forwarded-for. A log entry produced by this format will look like this:

Output

Here's an explanation of the information contained in the log message above:

  • -> : the hostname or IP address of the client that made the request.
  • -> : remote log name (name used to log in a user). A placeholder value () will be used if it is not set.
  • -> : remote username (username of logged-in user). A placeholder value () will be used if it is not set.
  • -> : the day and time of the request.
  • -> - the request method, route, and protocol.
  • -> - the response code.
  • -> - the size of the response in bytes.

Combined Log Format

The Combined Log Format is very similar to the Common log format but contains few extra pieces of information.

It's also defined in the configuration file:

You will observe the following output:

Output

Notice apache2 errorlog x-forwarded-for it is exactly the same as the Common Log Format, with the addition of two extra fields, apache2 errorlog x-forwarded-for. Entries produced in this format will look like this:

Output

Here's an explanation of the two additional fields that are not present in the Common log format:

  • -> : the URL of the referrer (if available, otherwise is used).
  • -> : detailed information about the user agent of the client that made the request.

Step 5 — Creating a custom log format

You can define a custom log format in the file by using the directive followed by the actual format of the output and a nickname that will be used as an identifier for the format, apache2 errorlog x-forwarded-for. After defining the custom format, you'll pass its nickname to the directive and restart the service.

In this example, we will create a log format named that looks like this:

Output

Open your file and place the line above below the other lines. It will produce access log entries with the following details:

  • : date and time of the request.
  • : the request protocol.
  • : the request method.
  • : the URL path requested.
  • : query parameters (if any).
  • : total bytes received including the request headers.
  • : final HTTP status code.
  • : number of bytes sent in the response.
  • : time taken to generate the response in milliseconds.

You can find all other formatting options and their description on this page.

To enable the custom format for subsequent access log entries, you must change the value of the directive in your virtual hosts file and restart the service with Systemctl.

Open up the default virtual hosts file using the command below:

Find the following line:

Output

And change it to:

Output

Save the file by pressing thenthen restart the service using the command below:

Afterward, make the following request to your server using :

You should observe the following response:

Output

Go ahead and view the last 10 messages in the access log file:

The log entry that describes the request will look like this:

Output

It's also possible to create multiple access log files by specifying the directive more than once. In the example below, the first line logs into a file using the log format, while the second uses the format to write entries into. Similarly, the file contains messages formatted according to the log format.

Output

Step 6 - Formatting your logs as JSON

Although many log management systems support the default Apache logging formats, apache2 errorlog x-forwarded-for, it might be best to log in a structured format like JSON since that's the go-to format for structured logging in the industry and it is universally supported. Here's a conversion of our log format into JSON:

Output

This produces log entries with the following formatting:

Output

Step 7 — Configuring Apache error logs

The server error log contains information about any errors that the web server encountered while processing incoming requests as well as other diagnostic information, apache2 errorlog x-forwarded-for. You can choose where the error messages will be transported to using the directive in your virtual host configuration file. This transport is usually a log file on the filesystem.

Here is an example from default virtual apache2 errorlog x-forwarded-for configuration file :

Output

On Debian-based distributions, the default error log is in the file, while in Fedora/CentOS/RHEL, it placed in the file. If the path argument to is not absolute, then it is assumed to be relative to the ServerRoot.

A common practice is to monitor the error log continuously for any problems during development or hasp error 1025. This is easily achieved through the command:

You will observe the following output:

apache2 errorlog x-forwarded-for Output

Aside from logging directly to a file, you can also forward your logs to a Syslog. You can do this by specifying instead of a file path as the argument to :

Step 8 — Customizing the error log format

Like the Apache access logs, the format of the error messages can be controlled through the directive, which should be placed in the main config file or virtual host entry. It looks like this:

Output

The above configuration produces a log entry in the following format:

Output

Here's an explanation of the formatting options used above:

: the apache2 errorlog x-forwarded-for time, including microseconds. : the log level of the message. : the process identifier. : the thread identifier. : the client IP address. : the actual log message.

Note that when the data for a formatting option is not available in a particular event, it will be omitted from the log entirely as the Apache error log doesn't use placeholder values for missing parameters.

You can find a complete description of all the available error formatting options in the Apache docs.

Step 9 — Customizing the error log apache2 errorlog x-forwarded-for the virtual host configuration file, apache2 errorlog x-forwarded-for, you can also control the level of messages that will be entered into the error log through the LogLevel directive. When you specify a particular value, messages from all other levels of higher severity will be logged as well, apache2 errorlog x-forwarded-for. For example, when is specified, messages with a severity of, and will also be logged.

These are the levels available in increasing order of severity:

  • - : trace messages (lowest severity).
  • : messages used for debugging.
  • : informational messages.
  • : normal but significant conditions.
  • : warnings.
  • : error conditions that doesn't necessarily require immediate action.
  • : critical conditions that requires prompt action.
  • : errors that require immediate apache2 errorlog x-forwarded-for system is unusable.

If the directive is not set, the server will set the log level to by default.

Step 10 — Centralizing your Apache logs

Storing your Apache logs on the filesystem may suffice for development environments or single-server deployments, but when multiple servers are involved, it may be more convenient to centralize all your logs in a single location so that you can automatically parse, filter, apache2 errorlog x-forwarded-for, and search log data from all sources in real-time.

In this section, we'll demonstrate how you can centralize your Apache logs in a log management service through Vector, a high-performance tool for building observability pipelines. The following instructions assume that you've signed up for a free Logtail account and retrieved your source token.

Go ahead and follow the relevant installation instructions for Vector for your operating system. On Ubuntu, you may run the following commands to install the Vector CLI:

After Vector is installed, apache2 errorlog x-forwarded-for, confirm that it is up and running through :

You should observe that it is active and running:

Output

Otherwise, go ahead and start it with the command below.

Afterwards, change into a root shell and append your Logtail vector configuration for Apache into the file using the command below, apache2 errorlog x-forwarded-for. Don't forget to replace the placeholder below with your source token.

Then restart the service:

You will observe that your Apache logs will start coming through in Logtail:

Streaming Apache logs to logtail

Conclusion

In this tutorial, you learned about the different types of logs that the Apache web server stores, where you can find those logs, and how to view their contents. We also discussed Apache access and error log formatting and how to create your custom log formats, including a structured JSON format. Finally, we considered how you can manage all your Apache logs in one place by using the Vector CLI to stream each entry to a log management service.

Don't forget to read the docs to find out more about all the logging features that Apache has to offer, apache2 errorlog x-forwarded-for. Thanks for reading!

Logs tell stories.
Read them.

Experience SQL-compatible
structured log management.

Explore logging →

Centralize all your logs into one place.

Analyze, correlate and filter logs with SQL.

Create actionable
dashboards with Grafana.

Share and comment with built-in collaboration.

Start logging

Got an article suggestion? Let us know

Share on TwitterShare on Facebookerror 040 duplicate case label value 14 alt="Share via e-mail" src="https://betterstack.com/packs/static/mail-f6c267f1db938513be41.png">

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How to View and Configure NGINX Access & Error Logs

Learn how to view and configure nginx access and error logs

Licensed under CC-BY-NC-SA

This work is licensed under a Creative Commons Attribution-NonCommercial-ShareAlike 4.0 International License.

Background

By default, our Load Balancer servertemplates will forward the 'X-Forwarded-For' HTTP header, which contains the source client IP address of the request, through to your backend application server. This IP address isn't logged anywhere by default though, so this article explains how we can add this header to the Apache access logs on the backend (application) servers in order to see where the request originated from.

Answer

In order to log the source IP from the X-Forwarded-For header on the app server, we will want to edit the Apache configuration file on your application server. This is normally located in:

Ubuntu: /etc/apache2/apache2.conf

Centos: /etc/httpd/conf/httpd.conf

Edit the file with a text editor and locate the 'LogFormat' lines, which defines how our access and error logs should output their content. By default, apache2 errorlog x-forwarded-for, we will be looking at the 'combined' LogFormat line, but you can add this to any LogFormat line you wish. It will look similar to this:

To add in the X-Forwarded-For, we will simply use the variable and integrate it into the LogFormat line, so you will want to change this line like so:

Save the change to the Apache config file, then restart/reload Apache. After a restart, view your access.log files, and you should notice that the source IP now being logged. Access logs are normally located in /var/log/apache2/ or /var/log/httpd/ (depending on distribution), though they may be elsewhere depending on templates used or app configuration.

Have questions or problems?

Call us at (866) 787-2253 or open up a support request from the RightScale dashboard by going to the Support -> Email link from the top right corner of the dashboard.

Apache Module mod_log_config

Summary

This module provides for flexible logging of client requests. Logs are written in a customizable format, and may be written directly to a file, apache2 errorlog x-forwarded-for, or to an external program, apache2 errorlog x-forwarded-for. Conditional logging is provided so that individual requests may be included or excluded from the logs based on characteristics of the request.

Three directives are provided by this module: to create a log file, to set a custom format, and to define a log file and format in one step. The and directives can be used multiple times in each server to cause each request to be logged to samp has crashed. the error files.

if then continue error 26 type mismatch alt="Support Apache!">

Topics

Directives

Bugfix checklist

See also

top

Custom Log Formats

The format argument to the and directives is a string. This apache2 errorlog x-forwarded-for is used to log each request to the log file. It can contain literal characters copied into the log files and the C-style control characters "\n" and "\t" to represent new-lines and tabs. apache2 errorlog x-forwarded-for Literal quotes and backslashes should be escaped with backslashes.

The characteristics of the request itself are logged by placing "" directives in the format string, which are replaced in the log file by the values as follows:

The percent sign.
Client IP address of the request (see the module).
Underlying peer IP address of apache2 errorlog x-forwarded-for connection (see the module).
Local IP-address.
Size of response in bytes, excluding HTTP headers.
Size of response in bytes, excluding HTTP headers. In CLF format, i.e. a post error occurs rather than a 0 when no bytes are sent.
The contents of cookie in the request sent to the server. Only version 0 cookies are fully supported.
The time taken to serve the request, in microseconds.
The contents of the environment variable .
Filename.
Remote hostname. Will log the IP address if is set to which is the default. If it logs the hostname for only a few hosts, you probably have access control directives mentioning them by name. See the Require host documentation.
Likebut always reports on the hostname of the underlying TCP connection and not any modifications to the remote hostname by modules like .
The request protocol.
The contents of header line(s) in the request sent to the server, apache2 errorlog x-forwarded-for. Changes made by other modules (e.g. ) affect this. If you're interested in what the request header was prior to when most modules would have modified it, use to copy the header into an internal environment variable and log that value with the described above.
Number of keepalive requests handled on this connection. Interesting if is being used, so that, for example, a '1' means the first keepalive request after the initial one, '2' the second, apache2 errorlog x-forwarded-for, etc.; otherwise this is always 0 (indicating the initial request).
Remote logname (from identd, if supplied). This will return a dash unless is apache2 errorlog x-forwarded-for and is set .
The request log ID from the error log (or '-' if nothing has been logged to the error log for this request). Look for the matching error log line to see what request caused what error.
The request method.
The contents of note from another module.
The contents of header line(s) in the reply.
The canonical port of the server serving the request.
The canonical port of the server serving the request, or the server's actual port, or the client's actual port. Valid formats are, or.
The process ID of the child that serviced the request.
The process ID or thread ID of the child that serviced the request. Valid formats are, andapache2 errorlog x-forwarded-for.
The query string (prepended with a if a query string exists, otherwise an empty string).
First line of request.
The handler generating the response (if any).
Status. For requests that have been internally redirected, this is the status of the original request, apache2 errorlog x-forwarded-for. Use for the final status.
Time the request was received, in the format. The last number indicates the timezone offset from GMT
The time, in the form given by format, which should be in an extended format (potentially localized). If the format starts with apache2 errorlog x-forwarded-for (default) the time is taken at the beginning of the request processing. If it starts with it is the time when the log entry gets written, close to the end of the request processing. In addition to the formats apache2 errorlog x-forwarded-for supported bythe following format tokens are supported:
number of seconds since the Epoch
number of milliseconds since the Epoch
number of microseconds since the Epoch
millisecond fraction
microsecond fraction
These tokens can not be combined with each other or formatting in the same format string. You can use multiple tokens instead.
The time taken to serve the request, in seconds.
The time taken to serve the request, in a time unit given by . Valid units are for milliseconds, for microseconds, and for seconds. Using gives the same result as without any format; using gives the same result as. Combining with a unit is available in 2.4.13 and later.
Remote user if the request was authenticated. May be bogus if return status () is 401 (unauthorized).
The URL path requested, not including any query string.
The canonical of the server serving the request.
The server name according to the setting.
Connection status when response is completed:
=Connection aborted before the response completed.
=Connection may be kept alive after the response is sent.
= Connection will be closed after the response is sent.
Bytes received, apache2 errorlog x-forwarded-for, including request and headers. Cannot be zero. You need to enable to use this.
Bytes sent, including headers, apache2 errorlog x-forwarded-for. May be zero in rare cases such as when a request is aborted before a response is sent. You need to enable to use this.
Bytes transferred (received and sent), including request and headers, cannot be zero, apache2 errorlog x-forwarded-for. This is the combination of %I and %O. You need to enable to use this.
The contents of trailer line(s) in the request sent to the server.
The contents of trailer line(s) in the response sent from the server.

Modifiers

Particular items can be restricted to print only for responses with specific HTTP status codes by placing a comma-separated list of status codes immediately following the "%". The status code list may be preceded by a "" to indicate negation.

Logs on 400 errors and 501 errors only. For an internal error occurred error code 16 other status codes, the literal string will be logged.
Logs on all requests that do not return one of the three specified codes, "" otherwise.

The modifiers "<" and ">" can be used for requests that have been internally redirected to choose whether the original or final (respectively) request should be consulted. By default, the directives and look at the original request while all others look at the final request. So for example, can be used to record the final status of the request and can be used to record the original authenticated user on a request that is internally redirected to an unauthenticated resource.

Format Notes

For security reasons, starting with version 2.0.46, non-printable and other apache2 errorlog x-forwarded-for characters in and are escaped using sequences, where stands for the hexadecimal representation of the raw byte. Exceptions from this rule are and which are escaped by prepending a backslash, and all whitespace characters, which are written in their C-style notation (,etc). In versions prior to 2.0.46, no escaping was performed on these strings so you had to be quite careful when dealing with raw log files.

Since httpd 2.0, unlike 1.3, the and format strings do not represent the number of bytes sent to the client, but simply the size in bytes of the HTTP response (which will differ, for instance, if the connection is aborted, or if SSL is used), apache2 errorlog x-forwarded-for. The format provided by will log the apache2 errorlog x-forwarded-for actual number of bytes sent over the network.

Note: is implemented as a quick-handler and not as a standard handler. Therefore, the format string will not return any handler information when content caching is involved.

Examples

Some commonly used log format strings are:

Common Log Format (CLF)
Common Log Format with Virtual Host
NCSA extended/combined log format
Referer log format
Agent (Browser) log format

You can use the directive multiple times to build up a time format using the extended format tokens like :

Timestamp including milliseconds
top

Security Considerations

See the apache2 errorlog x-forwarded-for tips document for details on why your security could be compromised if the directory where logfiles are stored is writable by anyone other than the user that starts the server.

top

BufferedLogsDirective

The directive causes to store several log entries in memory and write them together to disk, rather than writing them short jump is out of range error after each request. On some systems, this may result in more efficient spb mobile shell critical error access and hence higher performance. It may be set only once for the entire server; it cannot be configured per virtual-host.

This directive should be used with caution as a crash might cause loss of logging data.

top

CustomLogDirective

Description:Sets filename and format of log file
Syntax:
Context:server config, virtual host
Status:Base
Module:mod_log_config

The directive is used to log requests to the server. A log format is specified, and the logging can optionally be made conditional on request characteristics using environment variables.

The first argument, which minecraft error 1723 java the location to which the logs will be written, can take one of the following two types of values:

A filename, relative to the .
The pipe character "", apache2 errorlog x-forwarded-for, followed by the path apache2 errorlog x-forwarded-for to a program to receive the log information on its standard input. See the notes on piped logs for more information.

Security:

If a program is used, then it will be run as the user who startedapache2 errorlog x-forwarded-for. This will be root if the server was started by root; be sure that the program is secure.

Note

When pixma mp140 error 5100 a file path on non-Unix platforms, care should be taken to make sure that only forward slashed are used even though the platform may allow the use of back slashes. In general it is a good idea to always use forward slashes throughout the configuration files.

The second argument specifies what will be written to the log file. It can specify either a defined by a previous directive, or it can be an explicit string as described in the log formats section.

For example, the following two sets of directives have exactly the same effect:

# CustomLog with format nickname LogFormat "%h %l %u %t \"%r\" %>s %b" common CustomLog "logs/access_log" common # CustomLog with explicit format string CustomLog "logs/access_log" "%h %l apache2 errorlog x-forwarded-for %t \"%r\" %>s %b"

The third argument is optional and controls whether or not to log a particular request. The condition can be the presence or absence (in the case of a '' clause) of a particular variable in the server environment. Alternatively, the condition can be expressed as arbitrary boolean expression. If the condition is not satisfied, the request will not be logged. References to HTTP headers in the expression will not cause the header names to be added to the Vary header.

Environment variables can be set on a per-request basis using the and/or modules. For example, if you want to record requests for all GIF images on your server in a separate logfile but not in your main log, you can use:

SetEnvIf Request_URI \.gif$ gif-image CustomLog "gif-requests.log" common env=gif-image CustomLog "nongif-requests.log" common env=!gif-image

Or, to reproduce the behavior of the old RefererIgnore directive, you might use the following:

SetEnvIf Referer example\.com localreferer CustomLog "referer.log" referer env=!localreferer
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GlobalLogDirective

The directive defines a log shared by the main server configuration and all defined virtual hosts.

The directive is identical to the directive, apart from the following differences:

  • is not valid in virtual host context.
  • is used by virtual hosts that define their ownunlike a globally specified .
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LogFormatDirective

This station mode setting error specifies the format of the access log file.

The directive can take one of two forms. In the first form, where only one argument is specified, this directive sets the log format which will be used by logs specified in subsequent apache2 errorlog x-forwarded-for directives. The single argument can specify an explicit as discussed in the custom log formats section above. Alternatively, it can use a to refer to a log format defined in a previous directive as described below.

The second form of the directive associates an explicit with a . This can then be used in subsequent or directives rather than repeating the entire format string. A directive that defines a nickname does nothing else -- that is, it only defines the nickname, it doesn't actually apply the format and make it the default. Therefore, it will not affect subsequent directives. In addition, cannot use one nickname to define another nickname. Note that the nickname should not contain percent signs ().

Example

LogFormat "%v %h %l %u %t \"%r\" %>s %b" vhost_common
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TransferLogDirective

This directive has exactly the same arguments and effect as apache2 errorlog x-forwarded-for the directive, with the exception that it does not allow the log format to be specified explicitly or for conditional logging of requests. Instead, the log format is determined by the most recently specified directive which does not define a nickname. Common Log Format is used if no other format has been specified.

Example

LogFormat "%h %l %u %t \"%r\" %>s %b \"%{Referer}i\" \"%{User-agent}i\"" TransferLog logs/access_log
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Comments

Notice:
This is not a Q&A section, apache2 errorlog x-forwarded-for. Comments placed here should be pointed towards suggestions on apache2 errorlog x-forwarded-for the documentation or server, and may be removed by our moderators if they are either implemented or considered invalid/off-topic. Questions on how to manage the Apache HTTP Server should be directed at either our IRC channel, #httpd, on Libera.chat, or sent to our mailing lists.

Apache httpd (mod_proxy) seems to drop/ignore 3rd IP address in X-Forwarded-For chain?

Consider the scenario/flow:

As user's request traverses out of their network, the X-Forwarded-For (XFF) header is appended with IP address of each successive proxy. For example, when it arrives to the ALB the XFF header contains "192.168.1.100, 100.99.98.97". ALB will then append the ClientIP to this header, and in this case that is the IP of proxy2. Finally, when request arrives apache2 errorlog x-forwarded-for the reverse proxy sitting in front of my app, the XFF header is now: "192.168.1.100, apache2 errorlog x-forwarded-for, 100.99.98.97, 95.94.93.92".

Issue I'm seeing: At the reverse_proxyhttpd seems to be ignoring or dropping the last/most right IP in the X-Forwarded-For header chain, specifically when there are more than 2 addresses.

  • tcpdump at reverse apache2 errorlog x-forwarded-for shows the header contains full chain, so AWS ALB is doing what it should and appending proxy2's address.
  • when printing the XFF header in httpd access log, apache2 errorlog x-forwarded-for, I only see the first 2 addresses in the chain printed.
  • more importantly, when trying to take action on the expected third address, this tests fails, further proving (I think), apache2 errorlog x-forwarded-for, the 3rd address is dropped. By 'take action' I mean trying to invoke directive (mod_authz_host), after setting in the vhost.
  • If I remove from the flow, then I see address for in the XFF header at the reverse proxy without issue.

I'm not sure what I missed in my config or testing, and while not a standard, multiple addresses in XFF header is common. I face this issue only in Apache httpd 2.4. In version 2.2, this wasn't an issue and I can repeat the same setup/flow and I see all 3 addresses in the chain. Thanks in advance.

example vhost:

How to Get the Real Client IP Address from Cloudflare in Apache or PHP

Introduction

Cloudflare is great as a quick-and-easy CDN and DDoS protection, but one downside is that the IP address seen by your web server will be that of the Clouflare proxy apache2 errorlog x-forwarded-for not the actual client.

This can be a big security issue because your Apache access and error logs will only show apache2 errorlog x-forwarded-for IP of the Cloudflare proxy and not the actual client. Also, if you have IP restrictions in place defined in or a PHP script, these will not work.

Cloudflare sends the real client IP as in the HTTP header, and we can pass this on to PHP or Apache using .

Note: Cloudflare’s own Apache mod is now redundant and discontinued as Apache’s own mod  performs the same function.

PHP Script

You can easily fetch the real client IP in PHP with no further configuration required.

If you do this, and the validity of the visiting IP address is important, you might need to verify that the  contains an actual Cloudflare proxy IP address, because anyone can fake the header if they are able to connect directly to the server. See “Trusted Apache2 errorlog x-forwarded-for down the page for more info.

Apache

This configuration was tested on Ubuntu 20.04 and 18.04, but the process should be similar for any Debian-based web servers.

This method also works for Virtual Hosts. If you have multiple sites hosted and some do not use Cloudflare, Apache will simply default back to the Remote Address ().

Enable remoteip mod

Firstly, enable the mod.

Restart Apache:

Edit Config and Define Trusted Proxies

In order to pass the real client IP address from Cloudflare to Apache, we need to define the directive as in the configuration file .

Create the configuration file:

Simply add as the error no running copy line and then a list of trusted Cloudflare proxies below it (). As it’s easy for hackers to spoof in the http communication error minecraft 1.8, we need to make sure that Apache knows which proxies to apache2 errorlog x-forwarded-for. Cloudflare keeps an updated list of these proxies here: Cloudflare IPv4 Proxies and Cloudflare IPv6 Proxies.

/etc/apache2/conf-enabled/remoteip.conf

Save and exit (press  + , apache2 errorlog x-forwarded-for, press  and then press )

Restart Apache:

If Apache doesn’t detect in the HTTP header (e.g. if Cloudflare is turned off or not configured for a particular Virtual Host), it will fall back to the Remote Address ().

If Apache does detect  but it is coming from an IP not defined in (e.g. a hacker trying to spoof the headers), Apache will fall back to the Remote Address ().

Apache Access and Error Logs (optional)

You may not need to complete this step, but If you find that your access and error logs are showing the Cloudflare proxy IP instead of the remote user IP, you may need to do some further configuration.

Visit a page on your website in order to create an access log entry, then view the access log to see if it shows your IP or the Cloudfare proxy IP:

If it apache2 errorlog x-forwarded-for not showing your IP, continue below.

In order for the real client IP () to appear in andwe must make a small change to .

Edit :

Press + and search for .

The default log format should look something similar to below:

/etc/apache2/apache2.conf

The variable in red here is the Remote Apache2 errorlog x-forwarded-for. We just need to change this towhich is the Client IP as defined by the module.

/etc/apache2/apache2.conf

Save and exit (press  + , press  and then press )

Restart Apache:

To view the access log to see if it is now reporting :

Make sure that the Cloudlfare Proxy IP does not appear in the access log, but instead your own client IP.

If Apache doesn’t detect in the HTTP apache2 errorlog x-forwarded-for (e.g. if Cloudflare is turned off or not configured for a particular Virtual Host), the log will fall back to the Remote Address ().

If Apache does detect  but it is coming from an IP not defined in (e.g. a hacker trying to spoof the headers), the log will fall back to the Remote Address ().

Let me know if this helped. Follow me on Twitter, Facebook and YouTube, or 🍊 buy me a smoothie.

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