I’ve had a truenas server that’s been through many OS upgrades over the years, and not much actual use. In recent weeks I’ve been constantly getting notification emails that “Space usage for pool ‘freenas-boot’ is 95%.” and been trying to understand why.
My first attempt to see what might be taking space was shelling into the server playing around with du and df commands, but nothing was really eating up much space aside from maybe the /var and /usr directories. Then I discovered running sudo zfs list -r -o space,refer,written -t all freenas-boot from boot volume is almost full, after jail back up | TrueNAS Community which revealed a number of lines like freenas-boot/ROOT/OLD-TRUENAS-VERSION that were taking up gigabytes of space. Is there a safe way to delete these?
Longer answer: It is generally nice to have 2 prior boot environments available for trouble shooting.
However, if you upgraded your DATA pool features beyond what a prior boot environment supports, then those boot environments are more or less useless for booting back to. (But, those old boot environments can be helpful as online backups.)
My recommendation on upgrading DATA pool features, is to wait until such features are covered by all your boot environments. Enable only those features. Then, you can use the older boot environments as back out plans AND know that such features have been around a longer time, (with hopefully no or reduced bugs).
Note: You should never upgrade the boot-pool / freenas-boot feature set. Leave it as it was from installation, (or if the iX upgrade process does so automatically).
Correct, and that’s the first place you should look, because nothing else should be going on your boot device. At one time, it was fairly common to see FTP misconfiguration put everything into /root, which is on the boot pool, but I haven’t seen that come up in some time now.
So, yes: clear out old boot environments (maybe saving the last couple), and you should be good.
