| /var account cache crash games lock log opt run spool state tmp yp |
Variable data Process accounting logs (if supported) Application cache data System crash dumps (if supported) Variable game data Lock files Log files and directories User mailbox files Variable data for /opt Files relevant to running processes Application spool data Variable state information Temporary files preserved between system reboots Network Information Service (NIS) database files |
Tree 5.1
/var contains variable data files. This includes spool directories and files, administrative and logging data, and transient and temporary files.
Some portions of /var are not shareable between different systems. For instance, /var/log, /var/lock, and /var/run. Other portions may be shared, notably /var/mail, /var/cache/man, /var/cache/fonts, and /var/spool/news.
/var is specified here in order to make it possible to mount /usr read-only. Everything that once went into /usr that is written to during system operation (as opposed to installation and software maintenance) must be in /var.
If /var cannot be made a separate partition, it is often preferable to move /var out of the root partition and into the /usr partition. (This is sometimes done to reduce the size of the root partition or when space runs low in the root partition.) However, /var should not be linked to /usr because this makes separation of /usr and /var more difficult and is likely to create a naming conflict. Instead, link /var to /usr/var.
Applications should generally not add directories to the top level of /var. Such directories should only be added if they have some system-wide implication, and in consultation with the FHS mailing list.
The cache, lock, log, run, spool, state, and tmp directories must be included and used in all distributions; the account, crash, games, mail, and yp directories must be included and used if the corresponding applications or features are provided in the distribution.
Previous versions of the FHS included a /var/lib hierarchy. For further information, see the section on /var/state.
Several directories are `reserved' in the sense that they should not be used arbitrarily by some new application, since they would conflict with historical and/or local practice. They are:
/var/backups
/var/cron
/var/lib
/var/local
/var/msgs
/var/preserve