CUSTOM LOGROTATE RULES ALONGSIDE SYSTEM-WIDE CONFIGURATION

We frequently use logrotate to control log rotation on Linux servers. By default, logrotate use the custom configuration files locate in /etc/logrotate.d.

But what if we need a specific log file to be handled separately from the system-wide log rotation?

In this case, we can create a custom logrotate configuration file outside the /etc/logrotate.d directory.

Create a Custom Configuration File

sudo vim /apps/app_name/logrotate/app_name

Configure Log Rotation

In this new file, specify the log file, how frequently you want it to rotate, how many rotated versions to keep, and any other specific settings:

/apps/app_name/logs/log_name.log
{
    daily
    rotate 7
    # Add any other needed configurations here
}

Save the file and exit the text editor.

Configuration options

In a logrotate configuration file, you can use various options to customize the behaviour of log rotation. Here are some of the common options:

• compress: This option compresses the rotated log files using gzip or other compress utility. It is used to save disk space.

• copytruncate: This option allows logrotate to truncate the original log file after creating a copy, instead of moving or deleting it. This is useful for applications that do not support log file rotation.

• create: This option creates a new empty log file after rotation, if it does not exist. You can specify the permissions and owner/group for the new file.

• daily: Rotates the log file once a day. This is one of the frequency options. Other options include weekly, monthly, and yearly.

• dateext: Appends a date in YYYYMMDD format to the rotated log files. This is useful for keeping track of when each log was created.

• delaycompress: Postpones the compression of log files until the next rotation. This can be useful in conjunction with copytruncate to prevent race conditions.

• ifempty: Rotates the log file even if it is empty. By default, logrotate skips empty files.

• missingok: Ignores errors if the log file is missing.

• notifempty: Prevents log rotation if the log file is empty.

• rotate n: Specifies how many rotated versions of the log file to keep. For example, rotate 4 will keep four rotated log files.

• size: Rotates the log file when it reaches a specified size. You can use suffixes like k for kilobytes, M for megabytes, etc. For example, size 10M means rotate when the file reaches 10 megabytes.

• sharedscripts: Runs the postrotate script only once for all rotated logs, rather than once for each log.

• su: Specifies the user and group ownership of the log file after rotation. This can be used to change ownership if log files are created with elevated privileges.

• postrotate and prerotate: These options allow you to specify shell commands or scripts to be run before or after log rotation. For example, you could use postrotate to reload a service after log rotation.

• lastaction: This is similar to postrotate and prerotate but is run after all log files have been rotated.

These are some common options you can use in a logrotate configuration file. Depending on your specific needs, you may use a combination of these options to achieve the desired log rotation behaviour.

Verify Configuration

Check the syntax of your configuration file:

sudo logrotate -vdf /etc/logrotate_custom/custom_log

-vdf stands for:

• v: produce a detailed verbose output
• d: execute a dry-run, in other words, a simulation of which logrotate would do
• f: force the rotation even if the defined criteria are not met

Create a Cron Job

Open the crontab configuration for editing:

crontab -e

Add a line to schedule the execution of your custom log rotation at the desired time. For example, if you want to run it every day at 7 PM, add the following line:

0 19 * * * /usr/sbin/logrotate -f /apps/app_name/logrotate/app_name

Save and exit the editor.

With this setup, your custom log rotation for the /apps/app_name/logs/log_name.log file will occur at the time specified in the cron job, and it won’t be affected by the system-wide log rotation.