Linux: how to limit /var/log folder size

Sometimes the /var/log folder grows so large that it causes a shortage of disk space. How to limit the size of this folder? By following the two steps in this article, you can control the size of the /var/log folder.

Step 1. Limiting the size of journald logs

The logs of all systemd services are added to the /var/log/journal/ folder by the journald service. To set the size limit for this folder, run the following commands:

sudo bash -c 'echo "SystemMaxUse=100M" >> /etc/systemd/journald.conf'
sudo systemctl restart systemd-journald

Instead of the 100M size, you can specify any other size, in K, M, G, T units. After the above commands, you can verify that the size of the folder /var/log has become the specified size using the command:

du -sh /var/log/journal/

Step 2. Limiting the number of log files stored by logrotate

Logrotate rotates almost all log files in the /var/log folder every day. For example, if I type the command ls /var/log/kern*, then I will see that in addition to the file /var/log/kern.log I have 4 more files stored that logrotate saved:

ls /var/log/kern*

/var/log/kern.log    /var/log/kern.log.2.gz  /var/log/kern.log.4.gz
/var/log/kern.log.1  /var/log/kern.log.3.gz

To limit the number of log files, edit the file /etc/logrotate.d/rsyslog. Looking at the contents of the /etc/logrotate.d/rsyslog file, we can see that the default value of the rotate parameter is 4:

cat /etc/logrotate.d/rsyslog

/var/log/syslog
/var/log/mail.info
/var/log/mail.warn
/var/log/mail.err
/var/log/mail.log
/var/log/daemon.log
/var/log/kern.log
/var/log/auth.log
/var/log/user.log
/var/log/lpr.log
/var/log/cron.log
/var/log/debug
/var/log/messages
{
    rotate 4
    weekly
    missingok
    notifempty
    compress
    delaycompress
    sharedscripts
    postrotate
        /usr/lib/rsyslog/rsyslog-rotate
    endscript
}

You can change 4 to some other value, such as 1, so that only one file is stored. In the /etc/logrotate.d/ folder you will also find many other configuration files related to other log files, where you can also change the rotate setting.