On FreeBSD, you can jail a ZFS dataset – that is, the jail can manipulate the ZFS dataset as if it was a host (more or less). This has useful applications.
In my case, I want to backup a snapshot of that dataset from the host.
For example, I want to backup this dataset:
[12:19 r730-01 dvl ~] % zfs list data02/freshports/jailed/dev-ingress01/data/latest_commits NAME USED AVAIL REFER MOUNTPOINT data02/freshports/jailed/dev-ingress01/data/latest_commits 572K 798G 120K /var/db/ingress/latest_commits
Within the jail, the path to that dataset is /var/db/ingress/latest_commits. Indeed, within the jail, you can see the snapshots, including the one I want to backup ( snapshot-for-backup):
[12:21 dev-ingress01 dan /var/db/ingress/latest_commits] % cd .zfs/snapshot [12:21 dev-ingress01 dan /var/db/ingress/latest_commits/.zfs/snapshot] % ls autosnap_2023-12-25_06:00:02_hourly/ autosnap_2023-12-25_10:00:03_hourly/ autosnap_2023-12-25_11:15:02_frequently/ autosnap_2023-12-25_12:00:00_hourly/ autosnap_2023-12-25_07:00:08_hourly/ autosnap_2023-12-25_10:45:04_frequently/ autosnap_2023-12-25_11:30:04_frequently/ autosnap_2023-12-25_12:15:04_frequently/ autosnap_2023-12-25_08:00:03_hourly/ autosnap_2023-12-25_11:00:02_frequently/ autosnap_2023-12-25_11:45:00_frequently/ snapshot-for-backup/ autosnap_2023-12-25_09:00:10_hourly/ autosnap_2023-12-25_11:00:02_hourly/ autosnap_2023-12-25_12:00:00_frequently/ [12:21 dev-ingress01 dan /var/db/ingress/latest_commits/.zfs/snapshot] %
The problem to solve: how to go from this:
/var/db/ingress/latest_commits/.zfs/snapshot
to this:
/jails/dev-ingress01/var/db/ingress/latest_commits/.zfs/snapshot
when all you have is the dataset name:
data02/freshports/jailed/dev-ingress01/data/latest_commits
zfs get all
I know how to get this information about the dataset. Line 13 has the mount point. That’s part of what is needed.
[12:08 r730-01 dvl ~] % zfs get all data02/freshports/jailed/dev-ingress01/data/latest_commits NAME PROPERTY VALUE SOURCE data02/freshports/jailed/dev-ingress01/data/latest_commits type filesystem - data02/freshports/jailed/dev-ingress01/data/latest_commits creation Sun Dec 24 19:43 2023 - data02/freshports/jailed/dev-ingress01/data/latest_commits used 572K - data02/freshports/jailed/dev-ingress01/data/latest_commits available 798G - data02/freshports/jailed/dev-ingress01/data/latest_commits referenced 120K - data02/freshports/jailed/dev-ingress01/data/latest_commits compressratio 1.79x - data02/freshports/jailed/dev-ingress01/data/latest_commits mounted yes - data02/freshports/jailed/dev-ingress01/data/latest_commits quota none default data02/freshports/jailed/dev-ingress01/data/latest_commits reservation none default data02/freshports/jailed/dev-ingress01/data/latest_commits recordsize 32K inherited from data02/freshports/jailed/dev-ingress01 data02/freshports/jailed/dev-ingress01/data/latest_commits mountpoint /var/db/ingress/latest_commits local data02/freshports/jailed/dev-ingress01/data/latest_commits sharenfs off default data02/freshports/jailed/dev-ingress01/data/latest_commits checksum on default data02/freshports/jailed/dev-ingress01/data/latest_commits compression on inherited from data02 data02/freshports/jailed/dev-ingress01/data/latest_commits atime off inherited from data02 data02/freshports/jailed/dev-ingress01/data/latest_commits devices on default data02/freshports/jailed/dev-ingress01/data/latest_commits exec on default data02/freshports/jailed/dev-ingress01/data/latest_commits setuid on default data02/freshports/jailed/dev-ingress01/data/latest_commits readonly off default data02/freshports/jailed/dev-ingress01/data/latest_commits jailed on inherited from data02/freshports/jailed/dev-ingress01 data02/freshports/jailed/dev-ingress01/data/latest_commits snapdir hidden default data02/freshports/jailed/dev-ingress01/data/latest_commits aclmode discard default data02/freshports/jailed/dev-ingress01/data/latest_commits aclinherit restricted default data02/freshports/jailed/dev-ingress01/data/latest_commits createtxg 8714200 - data02/freshports/jailed/dev-ingress01/data/latest_commits canmount on default data02/freshports/jailed/dev-ingress01/data/latest_commits xattr on default data02/freshports/jailed/dev-ingress01/data/latest_commits copies 1 default data02/freshports/jailed/dev-ingress01/data/latest_commits version 5 - data02/freshports/jailed/dev-ingress01/data/latest_commits utf8only off - data02/freshports/jailed/dev-ingress01/data/latest_commits normalization none - data02/freshports/jailed/dev-ingress01/data/latest_commits casesensitivity sensitive - data02/freshports/jailed/dev-ingress01/data/latest_commits vscan off default data02/freshports/jailed/dev-ingress01/data/latest_commits nbmand off default data02/freshports/jailed/dev-ingress01/data/latest_commits sharesmb off default data02/freshports/jailed/dev-ingress01/data/latest_commits refquota none default data02/freshports/jailed/dev-ingress01/data/latest_commits refreservation none default data02/freshports/jailed/dev-ingress01/data/latest_commits guid 15864338690700456792 - data02/freshports/jailed/dev-ingress01/data/latest_commits primarycache all default data02/freshports/jailed/dev-ingress01/data/latest_commits secondarycache all default data02/freshports/jailed/dev-ingress01/data/latest_commits usedbysnapshots 452K - data02/freshports/jailed/dev-ingress01/data/latest_commits usedbydataset 120K - data02/freshports/jailed/dev-ingress01/data/latest_commits usedbychildren 0B - data02/freshports/jailed/dev-ingress01/data/latest_commits usedbyrefreservation 0B - data02/freshports/jailed/dev-ingress01/data/latest_commits logbias latency default data02/freshports/jailed/dev-ingress01/data/latest_commits objsetid 61452 - data02/freshports/jailed/dev-ingress01/data/latest_commits dedup off default data02/freshports/jailed/dev-ingress01/data/latest_commits mlslabel none default data02/freshports/jailed/dev-ingress01/data/latest_commits sync standard default data02/freshports/jailed/dev-ingress01/data/latest_commits dnodesize legacy default data02/freshports/jailed/dev-ingress01/data/latest_commits refcompressratio 1.95x - data02/freshports/jailed/dev-ingress01/data/latest_commits written 68K - data02/freshports/jailed/dev-ingress01/data/latest_commits logicalused 537K - data02/freshports/jailed/dev-ingress01/data/latest_commits logicalreferenced 114K - data02/freshports/jailed/dev-ingress01/data/latest_commits volmode default default data02/freshports/jailed/dev-ingress01/data/latest_commits filesystem_limit none default data02/freshports/jailed/dev-ingress01/data/latest_commits snapshot_limit none default data02/freshports/jailed/dev-ingress01/data/latest_commits filesystem_count none default data02/freshports/jailed/dev-ingress01/data/latest_commits snapshot_count none default data02/freshports/jailed/dev-ingress01/data/latest_commits snapdev hidden default data02/freshports/jailed/dev-ingress01/data/latest_commits acltype nfsv4 default data02/freshports/jailed/dev-ingress01/data/latest_commits context none default data02/freshports/jailed/dev-ingress01/data/latest_commits fscontext none default data02/freshports/jailed/dev-ingress01/data/latest_commits defcontext none default data02/freshports/jailed/dev-ingress01/data/latest_commits rootcontext none default data02/freshports/jailed/dev-ingress01/data/latest_commits relatime on default data02/freshports/jailed/dev-ingress01/data/latest_commits redundant_metadata all default data02/freshports/jailed/dev-ingress01/data/latest_commits overlay on default data02/freshports/jailed/dev-ingress01/data/latest_commits encryption off default data02/freshports/jailed/dev-ingress01/data/latest_commits keylocation none default data02/freshports/jailed/dev-ingress01/data/latest_commits keyformat none default data02/freshports/jailed/dev-ingress01/data/latest_commits pbkdf2iters 0 default data02/freshports/jailed/dev-ingress01/data/latest_commits special_small_blocks 0 default data02/freshports/jailed/dev-ingress01/data/latest_commits snapshots_changed Mon Dec 25 12:00:00 2023 -
What is missing
I think the missing information is the name of the jail (dev-ingress01) and the mountpoint (root) of that jail, relative to the host (/jails/dev-ingress01).
mount point
I think we can get the mountpoint from jls:
[12:28 r730-01 dvl ~] % jls -j dev-ingress01
JID IP Address Hostname Path
8 10.55.0.37 dev-ingress01.int.unixathome. /jails/dev-ingress01
Jailed into what jail
How can I find out what jail a given dataset is jailed with?
That’s the missing information.
I may move to non-jailed datasets for stuff which needs backing up this way.
