/cache contains Operating System managed, variable, binary data;
symbolic link farms and state.
It must be available during early boot to be used by init.
It should reside on the root filesystem or be mounted from the initrd.
It is assumed to be mounted read-write. It can be mounted read-only, but then it must be available for read-write during application of configuration updates and system updates.
It is not guaranteed to be shareable, but it can be, if the configuration of the shared systems is compatible.
In particular, this directory attempts to clean up existing abuse of
/etc. The intention is to keep /etc for only human readable and
human modifiable configuration, additions and overrides. And move all
cached and generated data out of the way. This should provide a
clearer separation of the Operating System provided defaults (/lib
and /usr), versus system administrator changes (/etc), versus the
combined state of the two (/cache). It also enables easier usage of
immutable, shared rootfs, and smaller /etc.
Applications may add directories to the top level of /cache, but not
individual files. Consultation with the
FHS-discuss mailing list is nonetheless advised, to
ensure cooperation across software providing or consuming similar
data.
There are no required directories in /cache.
/cache may contain directories, or symbolic links to directories.
/cache can also be empty, if none of the subsystems that use
/cache are installed or adopted its use.
Distributions may choose to optionally support and use /cache only in
certain configurations.
The following directories, or symbolic links to directories, may be in
/cache, if the corresponding subsystem is installed and in-use:
| Directory | Description |
|---|---|
/cache/apparmor |
AppArmor LSM binary compiled profiles |
/cache/certs |
X.509 public CA certificates bundles |
/cache/ldconfig |
ld.so dynamic linker cache files |
/cache/rcd |
LSB init.d script symbolic link farms and dependencies |
/cache/swap |
Linux Swap files |
See /cache/apparmor
See /cache/certs
See /cache/ldconfig
See /cache/rcd
See /cache/swap