98

I just got a message from the default disk analyses software (Baobab) that I only have 1GB left on the hard drive. After some search, I found that the /var/log/ folder is the cause of this.

Some file/sizes in /var/log/:

  • kern.log = 12.6 GB
  • ufw.log = 12.5 GB
  • kern.log.1 = 6.1 GB
  • ufw.log.1 = 6.0 GB

Et cetera et cetera. /var/log is huge.

Can I delete those files or the entire /var/log folder? Or is that a BIG NO NO in Ubuntu?

Improve this question

7 Answers 7

Reset to default
63

You must not remove the entire folder but you can remove "Old-Packed" log files without harming your system.

For a typical home user, it's safe to remove any log file that is compressed and has a .gz extension (as you can see in the picture).

These compressed log files are old logs that are gzipped to reduce storage space, and as an average user, you don't need them.

Select .gz extention

Improve this answer
12
  • 18
    find /var/log -type f -name "*.gz" -exec rm -f {} \;
    – diyism
    Jun 24, 2013 at 12:14
  • @diyism i tried your code, but not much help. my log dir still use 6GB space @_@
    – GusDeCooL
    Jan 9, 2014 at 4:11
  • 4
    find /var/log -type f -name "*.gz" -delete, I removed the compressed files and I only freed around 1 GB of space. Isn't 50 GB enough for the / dir and the rest of my disk for /home !
    – Muhammad Gelbana
    Feb 2, 2014 at 6:56
  • My mother's PC had a kern.log file 21 GB in size. A big kern.log indicates problem in the Linux kernel itself or in something it's experiencing issues in dealing with. In both cases, it's recommended to go to the Linux shell terminal and run cat /var/log/kern.log or nano /var/log/kern.log (at the GUI, run something like e.g. gedit /var/log/kern.log or mousepad /var/log/kern.log) and check what may be the problem. Once you figure out what's wrong you can then run sudo rm /var/log/kern.log ; sudo telinit 6 in order to delete such (big) file and restart the operating system.
    – Yuri Sucupira
    Mar 22, 2017 at 4:35
  • 3
    In my case, this will remove only 15.7 MB of 41 files. The real problems here are messages (7.7 GB), user.log (7.7 GB), syslog (4.1 GB) and syslog.1 (3.5 GB). Those four files sum 23 GB. Any way to remove them, or at least reduce their size?
    – Rodrigo
    Sep 11, 2017 at 18:39
40

I wouldn't delete the entire /var/log folder - that will break things.

You could just destroy the logs as @jrg suggests - but unless the things writing to the log files (mostly syslogd) are restarted that won't actually regain you any disk space, as the files will continue to exist in a deleted state until the filehandles are closed.

Better would be to find out why the logs aren't being rotated (and later deleted). logrotate is supposed to do this for you, and I suspect it's not being run each night as it should.

First thing I would do would be:

sudo /etc/cron.daily/logrotate

This should rotate the log files (so kern.log becomes kern.log.1); and you can then delete kern.log.1 etc to free up the disk space.

If everything is good so far, the next question is why this isn't happening automatically. If you turn your computer off at night, make sure you have anacron installed.

Improve this answer
2
33

DISCLAIMER: I am not an expert on this, use at own risk!

After finding that my /var/log/journal folder was taking several GB, I followed:

https://ma.ttias.be/clear-systemd-journal/

journalctl --vacuum-time=10d

which cleared 90%+ of it

Improve this answer
1
  • Works like a charm in Ubuntu 18, 20 and 22.
    – josircg
    Feb 15 at 19:20
19

You should look at the logs and see what is getting written to them. My guess is ufw/iptables (you are logging all network traffic).

ufw - when you log all packets, you will get large logs. If you are not going to review the logs, turn logging off. If you wish to monitor your network, use snort. Snort will filter through the thousands of packets you receive and alert you to potentially problematic traffic.

My guess it that ufw is the culprit and you are getting a large log in kern.log because you are logging packets there as well.

Sometimes there is a kernel or hardware problem that fills the logs. In that event it is best to fix the problem or file a bug, you will need to review the logs to do that.

If you can not fix the problem, you can configure syslog to as to not fill your logs.

See http://manpages.ubuntu.com/manpages/precise/man5/syslog.conf.5.html

If you provide more details on the problem we can help debug it better.

Improve this answer
1
  • 2
    That's a very good point. It's worth finding out what's clogging up the logs rather than just deleting them. +1.
    – richvdh
    Jan 30, 2012 at 23:06
8

Deleting /var/log is probably a bad idea, but deleting the individual logfiles should be OK.

On my laptop, with a smallish SSD disk, I set up /var/log (and /tmp and /var/tmp) as tmpfs mount points, by adding the following lines to /etc/fstab:

temp        /tmp        tmpfs   rw,mode=1777    0   0
vartmp      /var/tmp    tmpfs   rw,mode=1777    0   0
varlog      /var/log    tmpfs   rw,mode=1777    0   0

This means that nothing in those directories survives a reboot. As far as I can tell, this setup works just fine. Of course, I lose the ability to look at old logs to diagnose any problems that might occur, but I consider that a fair tradeoff for the reduced disk usage.

The only problem I've had is that some programs (most notably APT) want to write their logs into subdirectories of /var/log and aren't smart enough to create those directories if they don't exist. Adding the line mkdir /var/log/apt into /etc/rc.local fixed that particular problem for me; depending on just what software you have installed, you may need to create some other directories too.

(Another possibility would be to create a simple tar archive containing just the directories, and to untar it into /var/log at startup to create all the needed directories and set their permissions all at once.)

Improve this answer
1
  • 1
    ufw was the probleem apparently i set the logging to FULL so it logde everything. thanks for the help :)
    – blade19899
    Jan 31, 2012 at 19:00
7

I had and issue with enormous log files (like 100G each) with some useless messages from gnome 'cannot find video buffer' or something. Doing:

sudo rm -rf /var/log/user.log sudo rm -rf /var/log/syslog sudo rm -rf /var/log/messages

did not solve the problem, but doing systemctl restart syslog.service right after freed space used by those files.

Improve this answer
2
3

I had a several GBytes /var/log folder that I made shrink to less than 250MBytes using both /etc/systemd/journald.conf and logrotate:

config for journald: (cf man journald.conf)

SystemMaxUse=250M
SystemMaxFileSize=50M

config for /etc/logrotate.conf:

compress

/var/log/journal {
    daily
    dateext
    delaycompress
    copytruncate
    notifempty
    missingok
    rotate 3
    size 500k
    sharedscripts
}

also look into files in /etc/logrotate.d/*

Improve this answer
5
  • This isn't a solution. Even if you make this change to logrotete configuration, logfiles can grow to multi GB between logrotete is run - typecally once a day. Look in the largest of the active logfile (with tail -f filename.log) to determine what are the real problem, and then fix this promlem.
    – Soren A
    Feb 21, 2020 at 14:51
  • @SorenA $ du -sh /var/log now evaluates to 233M , whereas it was almost 5GB before. Maybe there remains issues for you, but it is a clearly a solution for the question about a "massive /var/log".
    – Stephane Rolland
    Feb 21, 2020 at 15:16
  • 1
    It's not professional to remove the symptom instead of the cause.You will end up with log-files with all kinds of "noise", or so short-lived, so that the day your sever have a real problem, the log-files don't contain the needed histiric data, or you can't find them among all the garbage.
    – Soren A
    Feb 21, 2020 at 17:35
  • @SorenA thanks for the remark. I peeked more closely at logs , and noticed a recurring error message which seems recurring often enough to be responsible for GBytes over months. Not crucial, but gotta fix this issue.
    – Stephane Rolland
    Feb 21, 2020 at 22:25
  • don't limit it too much, or you will not be able to find noise making apps, e.g.: sudo sed s/#SystemMaxUse=$/SystemMaxUse=500M/g /etc/systemd/journald.conf -i
    – rubo77
    Jun 1, 2022 at 7:35

You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .