/tmp and temporary files

/tmp is the directory for temporary files that programs need only for a short time. /var/tmp is for temporary files that should survive a reboot. On many distributions /tmp is cleared at boot or is a tmpfs in memory, and old files in both are removed by systemd-tmpfiles.

1/tmp versus /var/tmp

The Filesystem Hierarchy Standard says programs must not assume files in /tmp are kept between program runs, while /var/tmp is preserved across reboots. Both are writable by all users and have the sticky bit, so users can delete only their own files.

2Automatic cleaning

systemd-tmpfiles reads rules from tmpfiles.d directories, for example /usr/lib/tmpfiles.d/tmp.conf, which commonly sets an age of 10 days for /tmp and 30 days for /var/tmp. The cleaning runs daily through systemd-tmpfiles-clean.timer.

3tmpfs

When /tmp is mounted as tmpfs, its files live in RAM and swap and disappear at every reboot. findmnt /tmp shows whether it is a tmpfs.

How to check and clean /tmp

1. Check its size: sudo du -sh /tmp /var/tmp
2. See whether it is in memory: findmnt /tmp
3. Run the configured cleanup now: sudo systemd-tmpfiles --clean
4. List old files before deleting anything by hand: sudo find /tmp -type f -atime +10

Related articles

• Finding large and old files with findHow to use find to list big or old files on Linux, preview them safely and delete only what you checked.
• Disk usage with du and ncduHow to find what fills a Linux disk with du and the interactive ncdu, with options that stay on one file system.
• File permissions: chmod and chownHow Linux read, write and execute permissions work, what 755 and 644 mean, and how to change owner and mode safely.

Sources

1. tmpfiles.d(5) manual page man7.org
2. Filesystem Hierarchy Standard 3.0: /tmp refspecs.linuxfoundation.org

Note: RainServer offers monitoring and safe cleanup for Linux servers; it shows what will change and asks first.

Last reviewed: 2026-10-08