How to Clean Unmanaged Log Files

Warning:

– We are not responsible for any data loss that is caused by an attempt to perform these steps.
– We recommend that only experienced system administrators attempt to perform these steps.

Step 1: Check the disk space from the command line

Before you begin, ensure that you are logged in to the terminal as the root user.

Use the du command to see which files and directories consume the most space inside of the /var/log directory.

# du -h /var/log/

The du command prints the estimated disk space usage of each file and directory for the path that you specified.

The -h argument causes the command to print the information in a human-readable format. When you issue the command in the above example, the du utility prints the estimated disk space of each file and directory that the /var/log directory path contains.

Example:

The output of the du command should resemble the following example:

root@host [~]# du -h /var/log/
24K /var/log/cups
16K /var/log/mail
36K /var/log/prelink
19M /var/log/audit
84K /var/log/bandwidth/2011/Jun
128K /var/log/bandwidth/2011/Jan
116K /var/log/bandwidth/2011/Feb
712K /var/log/bandwidth/2011
4.5M /var/log/bandwidth
2.6G /var/log/munin
8.0K /var/log/conman.old
8.0K /var/log/pm
8.0K /var/log/conman
12K /var/log/dcpumon/boot.1308161402
5.3M /var/log/dcpumon
8.0K /var/log/vbox
3.7G /var/log/

Notes:
It is possible that you may see more output from the utility than the example shows. Due to the size of the files and directories in the /var/log directory path, the du utility may require some time to produce an output.

Step 2: Select the files or directories that you want to clear

You can clear individual files within a directory.

Example:

– The /var/log/munin directory uses 2.6 G of space, and is the second largest log on the list.
– Use the cd command to move the prompt to the /var/log/munin/ directory. Then, use the du -h * command to see the file sizes.

The output should resemble the following example:

root@host [~]# cd /var/log/munin/
root@host [/var/log/munin]# du -h *
603M munin-graph.log
385M munin-html.log
67M munin-limits.log
99M munin-node.log
1.5G munin-update.log

The du -h command, without the asterisk, shows the directory’s size.

The output should resemble the following example:

root@host [/var/log/munin]# du -h
2.7 G.

Step 3: Empty the files

Use the cat command (concatenate) to empty the log files or directories.

# cat /dev/null > munin-update.log

/dev/null is a non-existent file with no information.

When you concatenate /dev/null to a log file, you empty the file data, but do not delete the file name.

Example:

Empty a file:

The output from the previous example shows that the munin-update.log file occupies 1.5G of space in the drive.

To empty this file, use the cat command.

The output should resemble the following example:

root@host [/var/log/munin]# cat /dev/null > munin-update.log
root@host [/var/log/munin]#

To confirm that you successfully emptied the file, use the du -h * command.

The output should resemble the following example:

root@host [/var/log/munin]# cat /dev/null > munin-update.log
root@host [/var/log/munin]# du -h *
603M munin-graph.log
385M munin-html.log
67M munin-limits.log
99M munin-node.log
0M munin-update.log