Cache

Several cache mechanisms will be implemented but for now, ony one exists.

DirCache

This cache is based on a shared dir and requires no running daemon.

It must be initialized with a file LMAKE/size containing the overall size the cache is allowed to occupy. The value may end with a unit suffix in k, M, G, T (powers of 1024). For example LMAKE/size can contain 1.5T.

Permissions

For all users accessing the cache:

• The root dir of the cache and its LMAKE directory must have read/write access (including if only download is done to maintain the LRU state).
• The LMAKE/size must have read access.

If the group to use for access permission is not the default group of the users:

• the root of the cache must have this group, e.g. with chgrp -hR <group> <cache_dir>.
• its setgid bit must be set, e.g. with chmod g+s <cache_dir> <cache_dir>/LMAKE (this allows the group to propagate as sub-dirs are created)
• the operation above may have to be done recursively if the cache dir is already populated

To allow the group to have read/write access to all created dirs and files, there are 2 possibilities:

• Best is to the ACL's, e.g. using setfacl -d -R -m u::rwX,g::rwX,o::- <cache_dir>
• Altenatively, lmake.config.caches.<tag>.perm = 'group' can be set. This is slightly less performant as additional calls to chmod are necessary in that case.

Similarly, to allow the cache to be used by any user:

• Best is to the ACL's, e.g. using setfacl -d -R -m u::rwX,g::rwX,o::rwX <cache_dir>
• Altenatively, lmake.config.caches.<tag>.perm = 'other' can be set. This is slightly less performant as additional calls to chmod are necessary in that case.