Apache log where is it

The format string consists of percent directives, each of which tell the server to log a particular piece of information. Literal characters may also be placed in the format string and will be copied directly into the log output. The quote character " must be escaped by placing a backslash before it to prevent it from being interpreted as the end of the format string. The CustomLog directive sets up a new log file using the defined nickname.

The filename for the access log is relative to the ServerRoot unless it begins with a slash. This standard format can be produced by many different web servers and read by many log analysis programs. The log file entries produced in CLF will look something like this:.

Another commonly used format string is called the Combined Log Format. It can be used as follows. This format is exactly the same as the Common Log Format, with the addition of two more fields.

The access log under this format will look like:. Multiple access logs can be created simply by specifying multiple CustomLog directives in the configuration file. For example, the following directives will create three access logs. The first contains the basic CLF information, while the second and third contain referer and browser information.

This example also shows that it is not necessary to define a nickname with the LogFormat directive. Instead, the log format can be specified directly in the CustomLog directive.

There are times when it is convenient to exclude certain entries from the access logs based on characteristics of the client request. This is easily accomplished with the help of environment variables. First, an environment variable must be set to indicate that the request meets certain conditions. This is usually accomplished with SetEnvIf. Some examples:. As another example, consider logging requests from english-speakers to one log file, and non-english speakers to a different log file.

In a caching scenario one would want to know about the efficiency of the cache. A very simple method to find this out would be:. In that case a cache hit will log - , while a cache miss will log 1.

In other cases, a literal "-" will be logged instead. Likewise, in the second example, the Referer will be logged if the HTTP status code is not , , or Note the "! Although we have just shown that conditional logging is very powerful and flexible, it is not the only way to control the contents of the logs. Log files are more useful when they contain a complete record of server activity. It is often easier to simply post-process the log files to remove requests that you do not want to consider.

On even a moderately busy server, the quantity of information stored in the log files is very large. The access log file typically grows 1 MB or more per 10, requests. It will consequently be necessary to periodically rotate the log files by moving or deleting the existing logs. Just read across the line in your log file, and each entry can be decoded as above.

If there is no information, the log will display a hyphen. You can also create a custom log format by using the custom log module.

For more information about decoding log formats, see this page. Apache log analysis gives you the opportunity to measure the ways that clients interact with your website. For example, you might look at a timestamp to figure out how many access requests arrive per hour to measure traffic patterns. You could look at the user agent to find out if particular users are logging in to a website to access a database or create content.

You could even track failed authentications to monitor various types of cybersecurity attacks against your system. The apache error log can be used similarly. A error happens when a client requests a missing resource, and this can alert you on broken links or other errors within the page. In addition, as it is a standardized format in use by multiple web servers, CLF-formatted log files can be easily used by many log analysis platforms. Another format that is often used with Apache access logs is the Combined Log Format.

This format is very similar to the Common Log Format but contains a few extra fields to provide more information for use in analysis and debugging operations. An access log record that is recorded in the Combined Log Format looks something like this:.

As you can see, the first seven fields are identical to those in Common Log Format. The remaining fields represent two additional properties:.

Here, we defined the combined log format via the LogFormat directive, and we followed that up by defining the location and format combined for the access log using the CustomLog directive. As you can see, modifying the location or format of the access log is a straightforward process.

In addition, the use of the CustomLog directive affords us several other capabilities that we will describe below. This could be useful for a variety of reasons, including the exclusion of records associated with particular clients. Visit the official documentation on the CustomLog directive for more information. Like anything else on a server, log files take up space. And on a relatively busy Apache server, log files such as access logs can grow quickly.

Luckily, an Apache HTTP server has the ability to do this through the use of graceful restarts and piped log processes. A graceful restart of an Apache server allows for restarting without losing client connections. This restart enables Apache to open and write to new log files without client interruption, thereby allowing the execution of processing to compress or delete old log files in the interest of saving space.

Piped log processes, on the other hand, can allow for log rotation to be performed without a server restart; for example, a program called rotatelogs is included with Apache HTTP server. You should see a sample dashboard such as the one shown below:.

Using the GoAccess web interface, you can filter for specific information such as URL, operating system information, browser information, and more. In this guide, we discussed two simple steps to analyze Apache logs. If you are looking for a more visual and detailed method, check out our visualizing Apache Logs with ELK stack.

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