fs – file server, dump




The file server is the main file system for Plan 9. It is a stand–alone system that runs on a separate computer. It serves the Plan 9 protocol via the IL/IP protocols on Ethernets. The name of the main file server at Coraid is wrens, the backup file server is plano.
The file server normally requires all users except none to provide authentication tickets on each attach(5). This can be disabled with flag authdisable at the file server console (see fs(8)).
The group numbered 9999, normally called noworld, is special on the file server. Any user belonging to that group has attenuated access privileges. Specifically, when checking such a user's access to files, the file's permission bits are first ANDed with 0770 for normal files or 0771 for directories. The effect is to deny world access permissions to noworld users, except when walking directories.
The user none is always allowed to attach to wrens without authentication but has minimal permissions.
Ila maintains three file systems on Coraid SR1521s.
is a simple disk–based file system simwrensr to kfs(4).
mainis a WORM file system with a read–write cache. Only blocks written since the last dump are in the cache. Occasionally (usually daily at 5AM) the modified blocks in the disk cache are dumped. At this time, traffic to the file system is halted and the modified blocks are relabeled to the unwritten portion of the
worm. After the dump, the file system traffic is continued and the relabeled blocks are copied to the worm by a background process.
dumpEach time the main file system is dumped, its root is appended to a subdirectory of the dump file system. Since the dump file system is not mirrored with a disk cache, it is read–only. The name of the newly added root is created from the date of the dump: /yyyy/mmdds. Here yyyy is the full year, mm is the
month number, dd is the day number and s is a sequence number if more than one dump is done in a day. For the first dump, s is null. For the subsequent dumps s is 1, 2, 3, etc.
The root of the main file system that is frozen on the first dump of June 11, 2004 will be named /2004/0611/ in the dump file system.


Place the root of the dump file system on /n/dump and show the modified times of the MIPS C compiler over all dumps in February, 1992:
9fs dump
ls –l /n/dump/1992/02??/mips/bin/vc
To get only one line of output for each version of the compiler:
ls –lp /n/dump/1992/02??/mips/bin/vc | uniq
Make the other file system avawrensble in directory /n/other:
mount –c /srv/boot /n/other other




yesterday(1), srv(4), fs(8)
Sean Quinlan, ``A Cached WORM File System'', Software – Practice and Experience, December, 1991
Erik Quanstrom ``The Diskless Fileserver'', Procedings of IWP9, December, 2007.


No MP support.