NAME

	gefs – file server maintenance

SYNOPSIS

	check df halt help permit [ on | off ] save trace filename set [ snap ] key val clr [ snap ] key snap [ –mdl ] [ old [ new ] ] sync users

DESCRIPTION

	Gefs(4) provides an administration console on /srv/gefs.cmd. By default, this console is only readable and writable by the owner of the file system.

CONSOLE

The console handles the following commands: Check applies basic consistency checks to the file system, reporting invalid blocks, broken metadata, and other similar structural issues. Df prints the amount of used space and total space in megabytes, as well as the percentage of space occupied. Halt syncs all IO to disk and exits the file system. While the syncing occurs, the file system does not allow new writes. Help prints a summary of the available commands. This table includes additional debug commands that are subject to change, and are intentionally undocumented. Permit [ on | off ] has two effects. First, if the user table is broken, it allows a fallback to a default user list. This allows the system administrator to recover if they reboot with a broken user file. Second, it allows mounts to occur in permissive mode by any user. Permissive mounts are designated by prefixing the attach spec with a % sigil. Permissive disables permissions checks when accessing files, and allows wstat(5) to modify the owner of the file. This may be useful during file system initialization. Set or clr sets or clears a configuration key, respectively. If the snap name is passed, then the key is set in that snapshot. If not, then it is set globally. This key is a free form string which controls some aspect of file system behavior on that snapshot. All changes take effect after the file system is restarted. Currently, one configuration option is supported: retain'timespec' sets the schedule for which snapshots are retained. The timespec is a sequence of counts and intervals, in the form < count>@< interval>< scale>. Every interval, a new snapshot is taken. Up to count snapshots are retained in the history, with old ones aging out. If the count is omitted, then old snapshots are not trimmed. If the interval is omitted, it defaults to 1. Snapshot timing is taken from the config key attached to the snapshot. If there is no key attached to the snapshot, the global config key is used. If there is no global config key, the default value `60@1m 24@1h @1d' is used. Snap manages snapshots. It can be invoked as snap –l, snap –d snap, or snap [ –flags ] [[old] new], which will list, delete, or create new snapshots respectively. By default, the snap command creates a snapshot of old, tagging it with the name new. It accepts the following options: –l    Lists snapshots and their attributes. This flag accepts no arguments. –d snap Deletes a snapshot, reclaiming whatever space is not shared with other snapshots. This flag accepts a single argument, old, as the partition to delete. – m    Marks the newly created snapshot as mutable, rather than read–only. This flag only has an effect when tagging a new snapshot, and is ignored otherwise. Sync writes dirty blocks in memory to the disk. Users attempts to reload the user table from /adm/users. Save trace saves a trace of recent operations to a file. If a file is not specified, it prints to the console.

SNAPSHOTS

Snapshots are independent views of a filesystem hierarchy. A snapshot may be mutable or immutable. Mutable snapshots can be mounted and written to; immutable snapshots are a view of a file system hierarchy at a point in time. They are referred to by name, and are selected at mount time with an attach spec. When the attach spec starts with the % sigil, a snapshot is mounted in permissive mode. This allows the mounting user to bypass normal file system permission checks. In order to mount a snapshot in permissive mode, the mounting user must be in the adm group. There are several attach names that are reserved for the file system's internal use. All of these other than the main snapshot are required for the file system to work correctly, and may not be removed. dump:This is the name used to mount a list of all snapshots. Each snapshot in the file system will be listed in a directory. empty: This is a read–only empty snapshot. It contains no files or directories. The empty snapshot may be forked in order to create a new hierarchy, independent of other snapshots. adm:This is the snapshot where administrative files live. The users file is read at gefs startup, and define the users and groups for all snapshots. This file is described in detail in the following section. main:This snapshot is less special than the other special snapshots. It is created by default at file system mount time, and is the snapshot which is mounted when an attach specifier is not given. However, it is otherwise not special. It may be deleted, created, and freely modified. All snapshots are allocated from the same storage pool, and therefore share space.

ADM FILES

Gefs supports independent snapshots in the same file system. As a result, global configuration needs to be separated from snapshots. The global configuration resides in a well known snapshot called adm. The adm snapshot would conventionally be mounted in /adm. It contains the users(6) file. The users file is read at file system startup, or when the users command is run on the console. If the users file is malformed at file system start, then the file system will refuse to initialize. Permissive mode will allow the file system to fall back to a default users table. It will also allow any user to mount the adm snapshot: this can help recover from disasters. The default table looks like this: – 1:adm:adm: 0:none:: 1:$user:$user: Where $user is specified at the time that the file system is reamed.

EXAMPLES

To show current disk usage, the following may be written on the console: gefs# df To create a new snapshot: gefs# snap main myimmutable To create a new mutable snapshot that does not take automatic checkpoints: gefs# snap –m main mymutable gefs# set mymutable retain '' To delete a snapshot: gefs# snap –d mysnap To set the snapshot retention on the main snapshot to 12 snapshots taken every five minutes, along with 48 snapshots taken every 2 hours, and a daily snapshot with no trimming: gefs# set main retain '12@5m 48@2h @d' To set the default snapshot retention to daily, with no minute or hour snapshots: gefs# set retain @d To create a new user: # Mount the adm namespace (as a user in adm group): # and add the user to the user file % mount /srv/gefs /adm adm % sam /adm/users # From the console, reload the user table. # if there is an error in the user file, # an error will be printed on the console. % con –C /srv/gefs.cmd gefs# users refreshed users gefs# ^\ >>> q # Mount the file system in permissive mode to allow # changing file ownership, then create the user dir % mount /srv/gefs /n/u %main % mkdir /n/u/usr/$newuser % chgrp –u $newuser /n/u/usr/$newuser % chgrp $newuser /n/u/usr/$newuser # Create a tmp dir in the unsnapshotted 'other' # dataset. If it's present, the default namespace # will use it. % mount –c /srv/gefs /n/o %other % mkdir –p /n/o/usr/$newuser/tmp % chgrp $newuser /n/o/usr/$newuser^('' /tmp) % chmod 700 /n/o/usr/$newuser^('' /tmp)

BUGS

	Currently, it's not possible to change the mutability of a snapshot. Instead, a new label needs to be created.

SEE ALSO

	gefs(4)