Where are the main system log files located in CentOS?
Jul 19, 2025 am 03:56 AM
In CentOS, the system log files are mainly stored in the /var/log directory. Common ones include: 1. /var/log/messages record system messages; 2. /var/log/secure record authentication-related logs; 3. /var/log/dmesg record kernel information; 4. /var/log/cron record timing task information; 5. /var/log/boot.log record startup process. CentOS 7 and above use rsyslog to manage logs, combined with systemd's journald tool, it can be viewed through the journalctl command. It is also recommended to use logrotate rotation logs, real-time monitoring, remote centralized recording and other methods to optimize log management.
In CentOS, system log files are mostly stored under the /var/log directory. This is where most of the default logging happens for both the system itself and various services running on it.
Common Log Files You'll Encounter
CentOS uses a few standard log files that are useful for troubleshooting or monitoring system behavior. Here are some of the main ones:
- /var/log/messages – General system messages, including those logged during system startup.
- /var/log/secure – Authentication-related logs such as SSH login attempts, sudo usage, and other security events.
- /var/log/dmesg – Kernel ring buffer messages, which are especially helpful when diagnosed hardware or boot issues.
- /var/log/cron – Records cron job activity, useful for checking if scheduled tasks are running properly.
- /var/log/boot.log – Logs related to the system boot process (not always present by default, depending on configuration).
These files give you a good starting point when you need to investigate what's going on with your system.
How Logging Works in CentOS
CentOS 7 and later versions typically use rsyslog , an enhanced syslog daemon, to manage logging. It routes log messages from different sources into appropriate log files based on rules defined in its configuration file located at /etc/rsyslog.conf and any additional files in /etc/rsyslog.d/ .
If you're running systemd, another logging tool called journald is also active. It stores logs in a binary format and can be accessed using the journalctl command. For example:
-
journalctl -bshows logs from the current boot only. -
journalctl -u sshd.serviceshows logs related to the SSH service.
You can combine both journal logs and traditional log files for more detailed troubleshooting.
Tips for Managing System Logs
Log files can grow quickly, so here are a few tips to help you stay on top of them:
- Use
logrotateto automatically rotate and compress logs. Configuration files are usually found in/etc/logrotate.confand/etc/logrotate.d/. - Tail logs in real-time using
tail -f /var/log/messagesor similar commands for live monitoring. - Set up remote logging if you manage multiple servers—this helps centralize logs and make auditing easier.
- Don't ignore permissions: make sure sensitive logs like
/var/log/secureare readable only by root.
Also, be aware that some services may write logs outside of /var/log . For example, Apache might store logs under /var/log/httpd/ , while MySQL/MariaDB logs go into /var/log/mariadb/ .
That's pretty much how logging works in CentOS. The key locations and tools don't change much across versions, though newer releases might offer more integration with systemd-journald.
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