Re: I can get zfs snapshot/rollback in a jail to work 99% but it isn't quite 100% working. What am I missing?

So as I mentioned I’ve able to mail the dataset. It gets mounted upon
starting the jail. It shows up in “zfs list”. And when I do zfs snapshot on
the dataset it appears to create the snapshot as it shows up in a “zfs list
-t snapshot” but the snapdir isn’t visible even after setting snapdir to
visible, and when I rollback using the snapshot it doesn’t actually
rollback. I’m so close to this working, something just isn’t right and I
can’t figure out what. I really wish this was written up in the handbook.
“How to jail a dataset from the host” and “how to snapshot and rollback a
jailed dataset”. :) if I figure this I’ll definitely be writing this up.

Chris

On Mon, Nov 6, 2023 at 2:35 PM DtxdF <DtxdF@disroot.org> wrote:

> Hi Chris,
>
> Maybe your dataset is not mounted inside the jail. I thought that simply
> enabling `/etc/rc.d/zfs` was fine, but no, it just doesn't work. I don't
> know if this behavior is a bug or something else, but at the moment I don't
> have time to investigate.
>
> I have a similar setup for a jail with a delegated dataset. I use AppJail,
> but the steps are similar to other tools:
>
> ```
> # zfs create -o jailed=on -o mountpoint=/jailed zroot/jailed
> # appjail quick jtest \
> mount_devfs \
> device='include $devfsrules_hide_all' \
> device='include $devfsrules_unhide_basic' \
> device='include $devfsrules_unhide_login' \
> device='path zfs unhide' \
> template=template.conf \
> overwrite=force \
> start
> ```
>
> In AppJail, a template configuration file is similar to `jail.conf(5)`:
>
> ```
> # cat template.conf
> exec.start: "/bin/sh /etc/rc"
> exec.stop: "/bin/sh /etc/rc.shutdown jail"
> allow.mount
> allow.mount.zfs
> enforce_statfs: 1
> exec.poststart: "zfs jail ${name} zroot/jailed"
> exec.poststart+: "appjail cmd jexec ${name} zfs mount zroot/jailed"
> exec.prestop: "appjail cmd jexec ${name} zfs umount zroot/jailed"
> exec.prestop+: "zfs unjail ${name} zroot/jailed"
> ```
>
> As you can see, the dataset is mounted after running `zfs-jail(8)`. The
> steps are similar when the jail is stopped, but the dataset is unmounted
> and `zfs-unjail(8)` is executed.
>
> Inside the jail I can see the mounted datasets:
>
> ```
> # appjail cmd jexec jtest zfs list -r
> NAME           USED  AVAIL     REFER  MOUNTPOINT
> zroot         34.1G   249G       96K  /zroot
> zroot/jailed    96K   249G       96K  /jailed
> # appjail cmd jexec jtest mount -t zfs
> zroot/appjail/jails/jtest/jail on / (zfs, local, noatime, nfsv4acls)
> zroot/jailed on /jailed (zfs, local, noatime, nfsv4acls)
> # appjail cmd jexec jtest ls /jailed
> index.txt
> # appjail cmd jexec jtest cat /jailed/index.txt
> Hi!
> ```
>
> And I can use `zfs-rollback(8)` just fine:
>
> ```
> # appjail cmd jexec jtest zfs snapshot zroot/jailed@guard
> # appjail cmd jexec jtest zfs list -t snapshot zroot/jailed
> NAME                 USED  AVAIL     REFER  MOUNTPOINT
> zroot/jailed@guard     0B      -       96K  -
> # appjail cmd jexec jtest dd if=/dev/random of=/jailed/index.txt bs=16
> count=1
> 1+0 records in
> 1+0 records out
> 16 bytes transferred in 0.000102 secs (157318 bytes/sec)
> # appjail cmd jexec jtest hd /jailed/index.txt
> 00000000  a1 26 2a 9c f5 96 7b 81  90 8d ba 36 d6 f9 4d 93
> |.&*...{....6..M.|
> 00000010
> # appjail cmd jexec jtest zfs list -t snapshot zroot/jailed
> NAME                 USED  AVAIL     REFER  MOUNTPOINT
> zroot/jailed@guard    56K      -       96K  -
> # appjail cmd jexec jtest zfs rollback zroot/jailed@guard
> # appjail cmd jexec jtest hd /jailed/index.txt
> 00000000  48 69 21 0a                                       |Hi!.|
> 00000004
> ```
>
> I hope this can help you.
>
>
> ~ DtxdF
>
>
> El 6 de noviembre de 2023 6:07:06 p. m. UTC, Chris Watson <
> bsdunix44@gmail.com> escribió:
>
>> I've been trying to get a zfs dataset delegated into a jail (to run PG
>> on), and allow snapshots and rollback to take place inside the jail. I can
>> get the dataset mounted into the jail, I can get zfs to take the snapshot,
>> list the snapshot, but when I rollback or try to ls -la the directory to
>> see the '.zfs' dir it isn't there and the zfs rollback completes but it
>> doesn't actually rollback. I'm so close to getting this to work! I'm just
>> missing *something* in the sauce. When I do the zfs rollback zfs looks like
>> it completes the rollback and goes back to a shell prompt but the files I
>> remove before the rollback are not in the /var/db/postgres/data16 directory
>> nor is ".zfs" shown in ls -la. So something is wonky on my end. I'm so
>> close, it's halfway there, it looks like it takes a snapshot, the snapshot
>> shows up in a zfs list -t snapshot, but it's also not really there. I'm
>> doing something just slightly wrong here. I just cant figure out what I
>> have wrong.
>>
>> Below are the configs:
>> # The jail's config
>> https://bsd.to/P176
>> # zfs list from inside the jail
>> https://bsd.to/mPde
>> # zfs list -t snapshot from inside the jail
>> https://bsd.to/R8dw
>> # ls -la /var/db/postgres/data16 output from inside the jail
>> https://bsd.to/1di2
>> # rc.conf of the jail
>> https://bsd.to/JcnH
>>
>> The jail is running 13.2-P4.
>> Using bastillebsd 0.10.20231013 for creation/management.
>>
>> Thanks!
>> Chris
>>
>