How is the /tmp directory cleaned up?
My temporary files never get written to the disk. They get written to a RAM disk. I did put tmpfs /tmp tmpfs defaults,noatime,mode=1777 0 0 in /etc/fstab.
8 Answers 8
Note! This answer is outdated since at least ubuntu 14.04. See other answers for current situation and if they prove correct then upvote them furiously. Also post comment so I can put link here to current correct answer.
The cleaning of /tmp is done by the upstart script /etc/init/mounted-tmp.conf . The script is run by upstart everytime /tmp is mounted. Practically that means at every boot.
The script does roughly the following: if a file in /tmp is older than $TMPTIME days it will be deleted.
The default value of $TMPTIME is 0, which means every file and directory in /tmp gets deleted. $TMPTIME is an environment variable defined in /etc/default/rcS .
@Martin Schröder — the script exists on my system & it is a clean install of 14.04 and tmpreaper doesn’t exist!
I am using arch linux now so I cannot verify. Sorry. Please someone verify this and comment or edit my answer.
in ubuntu 16.04 tmpreaper is abandoned as un-secure please see: fossies.org/linux/tmpreaper/debian/README.security
No. In Ubuntu 16.04 it is simply superseded by a systemd mechanism. Read that document, and what you will actually find is an explanation of why the security analysis claiming insecurity is flawed.
The directory is cleared by default at every boot, because TMPTIME is 0 by default.
Here you can change the time in the following file:
TMPTIME says how frequent the tmp dir sould be cleared in days
Clearing at every boot is not ideal for a machine that is never rebooted, like a server. I’ve got over 500,000 files taking 5Gb space in my /tmp because my server has 378 days uptime. I’m reluctant to reboot it, simply because clearing those files on reboot make take hours.
While the /tmp folder is not a place to store files long-term, occasionally you want to keep things a little longer than the next time you reboot, which is the default on Ubuntu systems. I know a time or two I’ve downloaded something to /tmp during testing, rebooted after making changes and then lost the original data again. This can be changed if you’d like to keep your /tmp files a little bit longer.
Changing the /tmp Cleanup Frequency
The default setting that tells your system to clear /tmp at reboot is held in the /etc/default/rcS file. The value we’ll look at is TMPTIME .
The current value of TMPTIME=0 says delete files at reboot despite the age of the file. Changing this value to a different (positive) number will change the number of days a file can survive in /tmp .
This setting would allow files to stay in /tmp until they are a week old, and then delete them on the next reboot. A negative number ( TMPTIME=-1 ) tells the system to never delete anything in /tmp . This is probably not something you want, but is available.
good explanation. But in which script is the cleanup command? I have seen /etc/init/mounted-temp.conf , but it has the line start on mounted MOUNTPOINT=/tmp that make me think it is non applicable.
It’s also handy to keep files you don’t want to lose (rendered video frames) when your machine crashes, possibly due to OOM. A better solution would be to fix the problem, of course. 🙂
I think it would be better to keep such longer-term temp files in /var/tmp (as Gilles said). Then you can mount /tmp as tmpfs (as Arch Linux does).
I’m checking this on Ubuntu 16.10. I can certify that editing /etc/default/rcS has no effect at all anymore and the files in tmp are wiped out by reboot no matter what you put in that file. As others mention, tmpreaper is no longer used.
I think the right answer is that Ubuntu 16.10 has a new setup. There is a folder /etc/tmpfiles.d, documented in the man page «tmpfiles.d». In that folder, one should place a configuration file to control whether the /tmp is to be erased. This is what I am doing to stop reboots from erasing files in /tmp unless they are 20 days old:
#/etc/tmpfiles.d/tmp.conf d /tmp 1777 root root 20d Replace «20d» by «-» if you never want files deleted. This is my best effort, that man page is nearly impenetrable with detail.
The advantage of the new setup is that a file cleaner can still run even if the system is not rebooted (as in the case of an always on server). That’s a big plus, I think.
I found that you can preserve the original file permissions and owner by using hyphens: d /tmp/ — — — 20d
Also worth noting: you can test your configuration by running the cleaning job manually: systemctl start systemd-tmpfiles-clean
Creating /etc/tmpfiles.d/tmp.conf overrides /usr/lib/tmpfiles.d/tmp.conf causing the configuration for the other directories there to be lost if not copied (e.g., /var/tmp/systemd-private-%b-* ). See the source.
In Ubuntu 14.04 this is done by tmpreaper , which is called daily by cron (from /etc/cron.daily ). The program can be configured via /etc/default/rcS and /etc/tmpreaper.conf .
In a systemd Ubuntu (15.10 and newer), this is done by systemd, using the systemd-tmpfiles-clean service and timer:
$ systemctl cat systemd-tmpfiles-clean.service # /lib/systemd/system/systemd-tmpfiles-clean.service # This file is part of systemd. # # systemd is free software; you can redistribute it and/or modify it # under the terms of the GNU Lesser General Public License as published by # the Free Software Foundation; either version 2.1 of the License, or # (at your option) any later version. [Unit] Description=Cleanup of Temporary Directories Documentation=man:tmpfiles.d(5) man:systemd-tmpfiles(8) DefaultDependencies=no Conflicts=shutdown.target After=local-fs.target time-sync.target Before=shutdown.target [Service] Type=oneshot ExecStart=/bin/systemd-tmpfiles --clean IOSchedulingClass=idle $ systemctl cat systemd-tmpfiles-clean.timer # /lib/systemd/system/systemd-tmpfiles-clean.timer # This file is part of systemd. # # systemd is free software; you can redistribute it and/or modify it # under the terms of the GNU Lesser General Public License as published by # the Free Software Foundation; either version 2.1 of the License, or # (at your option) any later version. [Unit] Description=Daily Cleanup of Temporary Directories Documentation=man:tmpfiles.d(5) man:systemd-tmpfiles(8) [Timer] OnBootSec=15min OnUnitActiveSec=1d You can change the timer behaviour itself using systemctl edit systemd-tmpfiles-clean.timer , and using various systemd Timer configuration options (see man 5 systemd.timer ).
So systemd-tmpfiles-clean runs on shutdown, and once per day otherwise. The files it cleans can be extended using /etc/tmpfiles.d (mentioned in another answer).
It’s interesting to note that as default /etc/tmpfiles.d is empty. The file where the /tmp policy is defined is here:
# This file is part of systemd. # # systemd is free software; you can redistribute it and/or modify it # under the terms of the GNU Lesser General Public License as published by # the Free Software Foundation; either version 2.1 of the License, or # (at your option) any later version. # See tmpfiles.d(5) for details # Clear tmp directories separately, to make them easier to override D /tmp 1777 root root - #q /var/tmp 1777 root root 30d So, as already noted, to override it, you can see the other answer about tmpfiles.d.
How to clean /tmp?
will delete all files and folders older than 10 days. you may want to add it to the daily cron.
UPDATE
In comments below @sfussenegger recommends a slightly different format of this command that may be better suited to your needs and to the system you’re operating on.
sudo find /tmp -type f -atime +10 -delete
Here the command is using sudo to make sure everything is deleted (or you could run it as root), operating on files that haven’t been accessed for more than 10 days and only deletes files, not folders. It also uses -delete to avoid having to execute rm command
instead of creation time (-ctime) you may want to use access time (-atime) instead — of course only if the filesystem keeps this information (check for noatime in /etc/fstab)
ok, please bear with me but there’s one more thing: you want to search files only ( -type f ). otherwise you may find that the parent of a directory tree hasn’t been accessed in a while and delete all its content that could potentially still be in use. so the final command I’d recommend is sudo find /tmp -type f -atime +10 -delete
@sfussenegger, perhaps your could promote your comments to an answer? I think it is better than being «hidden» in the comments.
You can assume that anything inside a tmp directory (/tmp/ /usr/tmp etc) can be deleted. BEFORE you start deleting stop all programs and services you are using since /tmp/ can be used by programs to temporarily store information for that session. So do a sudo service mysql stop and sudo service apache2 stop if you have a mysql and/or apache running. The name of the files in the /tmp/ directory most times give a clue to what program they belong.
will empty the /tmp/ directory and remove all files and subdirectories. Be careful to type it correctly. The command pwd in there is not necessary but should show /tmp .
If you want it interactively (so you need to confirm deleting):
Also worth noting that a reboot will clear /tmp aswell as shown here: How is the /tmp directory cleaned up? So if /tmp/ is full of files after a reboot you need to investigate where those files originate from.