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Jails snapshot (zfs-only)

jsnapshot command

% cbsd jsnapshot

Description:

A variety of operations on jails become available through jsnapshot when the node is kept on a ZFS filesystem and zfsfeat is set to 1 in $workdir/nc.inventory. The mode parameter is used to specify which of the following actions are taken:

  • list — show a list of existing snapshots for the selected jail
  • create — create a snapshot
  • destroy — delete a specific snapshot of the jail
  • destroyall — remove all of the jail's snapshots
  • clone — clone an existing snapshot into new jail
  • rollback — rollback the selected jail to current snapshot state

Additional arguments:

  • jname — specifies the jail upon which the action will be performed
  • snapname — gives the snapshot a name

It should be kept in mind that snapshots follow a tree structure. This means, if you created a series of snapshots : 1,2,3,4 and roll back to snapshot 2, then the snapshots 3 and 4 will be lost, since from the point of snapshot 2 they did not exist yet. Also use a unique name for a snapshot at creation. You can specify snapname=gettimeofday. In this case, the system automatically sets the current timestamp as the name for the new snapshot. When listing snapshots, you can use modifiers to customize output fields with arguments to display=

Example:

create snapshot named gromozeka for jail1 jail:

% cbsd jsnapshot mode=create jname=jail1 snapname=gromozeka

create snapshot named zelepuka for jail1 jail:

% cbsd jsnapshot mode=create jname=jail1 snapname=zelepuka

Run jail1 and stop after some modification:

% cbsd jstart jail1
..
% cbsd jexec jname=jail1 cp /bin/date /root
% cbsd jexec jname=jail1 file -s /root/date
/root/date: ELF 64-bit LSB executable, x86-64, version 1 (FreeBSD), dynamically linked (uses shared libs), for FreeBSD 9.0 (900506), stripped
% cbsd jstop jail1
..

Rollback jail1 to snapshot zelepuka state:

% cbsd jsnapshot mode=rollback snapname=zelepuka jname=jail1
% cbsd jstart jail1
...
% cbsd jexec jname=jail1 file -s /root/date
/root/date: ERROR: cannot open `/root/date' (No such file or directory)