ref: 9ff7598b92db75af690f20caeb41fae9ed9acdb2
dir: /sys/man/8/gefs/
.TH GEFS 8 .SH NAME gefs \- file server maintenance .SH SYNOPSIS .PD 0 .PP .B check .PP .B df .PP .B halt .PP .B help .PP .B permit [ .B on | .BR off ] .PP .B save trace .I filename .PP .B snap [ -Smdl ] [ .I old [ .I new ] ] .PP .B sync .PP .B users .SH DESCRIPTION .IR Gefs (4) provides an administration console on .IR /srv/gefs.cmd . By default, this console is only readable and writable by the owner of the file system. .SH CONSOLE .PP The console handles the following commands: .PP .I Check applies basic consistency checks to the file system, reporting invalid blocks, broken metadata, and other similar structural issues. .PP .I Df prints the amount of used space and total space in megabytes, as well as the percentage of space occupied. .PP .I Halt syncs all IO to disk and exits the file system. While the syncing occurs, the file system does not allow new writes. .PP .I Help prints a summary of the available commands. This table includes additional debug commands that are subject to change, and are intentionally undocumented. .PP .I Permit [ .B on | .B 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 .I % sigil. Permissive disables permissions checks when accessing files, and allows .IR wstat (5) to modify the owner of the file. This may be useful during file system initialization. .PP .B Snap manages snapshots. It can be invoked as .I snap .BR -l , .I snap .B -d .IR snap , or .I snap [ .B -flags ] .IR "[[old] new]" , which will list, delete, or create new snapshots respectively. By default, the .I snap command creates a snapshot of .IR old , tagging it with the name .IR new . It accepts the following options: .TP .B -l Lists snapshots and their attributes. This flag accepts no arguments. .TP .BI "-d " snap Deletes a snapshot, reclaiming whatever space is not shared is not shared with other snapshots. This flag accepts a single argument, .IR old , as the partition to delete. .TP .B -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. .TP .B -S Disables automatic timed snapshots. This flag only has an effect when tagging a new snapshot, and is ignored otherwise. .PP .I Sync writes dirty blocks in memory to the disk. .PP .B Users attempts to reload the user table from .IR /adm/users . .PP .I Save trace saves a trace of recent operations to a file. If a file is not specified, it prints to the console. .SH 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 im time. They are referred to by name, and are selected at mount time with an attach spec. When the attach spec starts with the .B % 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 .I adm group. .PP There are several attach names that are reserved for the file system's internal use. All of these other than the .I main snapshot are required for the file system to work correctly, and may not be removed. .TP .I 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. .TP .I 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. .TP .I adm: This is the snapshot where administrative files live. The .I 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. .TP .I 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. .PP All snapshots are allocated from the same storage pool, and therefore share space. .SH ADM FILES .PP 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 .IR adm . .PP The adm snapshot would conventionally be mounted in .IR /adm . It contains the .IR users (6) file. .IR The .I users file is read at file system startup, or when the .I 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. .I Permissive mode will allow the file system to fall back to a default users table. It will also allow any user to mount the .I adm snapshot: this can help recover from disasters. .PP The .B default table looks like this: .IP .EX -1:adm:adm: 0:none:: 1:$user:$user: .EE .PP Where .I $user is specified at the time that the file system is reamed. .SH EXAMPLES .PP To show current disk usage, the following may be written on the console: .IP .EX gefs# df .EE .PP To create a new snapshot: .IP .EX gefs# snap main myimmutable .EE .PP To create a new mutable snapshot that does not take automatic checkpoints: .IP .EX gefs# snap -Sm main mymutable .EE .PP To delete a snapshot: .IP .EX gefs# snap -d mysnap .EE .PP To create a new user: .IP .EX # mount the adm namespace (as a user in adm group): # and add the user to the user file % mount /srv/gefs /adm adm % sam /adm/users # create the user home directory # and tmp snapshot % mount /srv/gefs /n/u %main % mkdir /n/u/usr/$newuser % chgrp -u $newuser /n/u/usr/$newuser % chgrp $newuser /n/u/usr/$newuser .EE .SH BUGS .PP Currently, it's not possible to change the mutability of a snapshot. Instead, a new label needs to be created. .PP .SH SEE ALSO .IR gefs (4)