2024-02-06 cleanup of products ssnapshots on off2

It's been a while since we migrated off products to off2.

Previous snapshot system did not use sanoid. So there are several old snapshot that we should remove.

We can see snapshots with

zfs list  -r zfs-nvme/off/products -t snap -o name|grep -v autosnap

I see the old snapshots that looks like @20231122-1906. I want to keep one snapshot per month, but I will rename it to look like a sanoid snapshot. (so sanoid will clean it according to retention policy).

doing it manually it looks like this kind of command:

zfs rename zfs-nvme/off/products@20231101-0000 zfs-nvme/off/products@autosnap_2023-11-01_00:00:00_monthly

or more automatic (on off-pro products):

# remove the echo in front of zfs rename when you have tested it
for m in 0{5..9} 1{0,1};do echo zfs rename zfs-nvme/off-pro/products@2023${m}01-0000 autosnap_2023-${m}-01_00:00:00_monthly; done

Then I remove the old snapshots:

# remove the echo in front off zfs destroy when you have tested it
for f in $(zfs list  -r zfs-nvme/off/products -t snap -o name);do [[ $f == *"@2023"* ]] && echo $f && echo zfs destroy $f;done

I did it for off, off-pro, opf, opff and obf.

I then disable snapshot_purge from crontab.