zpool cache not respected by opnsense

[nt1]

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Describe the bug

zpools other than zroot present in zpool cache (/etc/zfs/zpool.cache or /boot/zfs/zpool.cache) are not imported at boot time in OPNsense 24.1.9.

To Reproduce

Steps to reproduce the behavior:

1. Access command line of device and get a root shell.
2. Create a new zpool.
3. Export the zpool (zpool export )
4. Import the zpool (zpool import )
5. Verify the zpool exists in zpool cache (zdb -U /etc/zfs/zpool.cache)
6. Reboot the system.
7. When the system is back up, access the command line and check if the new zpool was imported (zpool list). Notice only zroot exists.

Expected behavior

Upon reboot, the newly created zpool was imported.

Describe alternatives you considered

It is possible to manually import the zpool using zpool import after the reboot, but this doesn't really scale.

I was able to get the pool to import as expected by adding zfs_enable="YES" to /etc/rc.conf which allowed /etc/rc.d/zfs to start at boot per expectations. I notice opnsense sets this variable in /usr/local/etc/rc.loader.d/20-zfs, perhaps this variable isn't making it to freebsd's rc.d?

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Relevant log files

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Additional context

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Environment

Software version used and hardware type if relevant, e.g.:

OPNsense 24.1.9

[fichtner]

The code you may want to improve is this:

core/src/etc/rc

Lines 153 to 160 in 0f73da0

	if kldstat -qm zfs; then
	mount -uw /
	zpool import -Na
	zfs mount -va
	# maybe there is a mountpoint in fstab
	# that requires ZFS to be fully set up
	mount -a
	fi

Do not confuse _load with _enable vars. We don’t use the RC subsystem that much as it tends to interfere with the boot sequence.

[nt1]

Adding -c CACHE_FILE to the referenced zpool import and removing changes to /etc/rc.conf fixes my issue. However, I'm fairly certain that adding additional pools worked in a previous release of OPNSense with no changes.

The behavior of zpool import -a changed when OpenZFS was adopted in FreeBSD 13. In prior releases, -a would default to searching for pools in /dev:
https://github.com/freebsd/freebsd-src/blob/b5ad6b488d9e62d820fe90fdce4aee4f4d3d7162/cddl/contrib/opensolaris/cmd/zpool/zpool_main.c#L2634

This changes in OpenZFS, used in 13+, the environment variable ZPOOL_IMPORT_PATH is used as the search path:
https://github.com/freebsd/freebsd-src/blob/5fe9c9de03ef3191d216964bc4d8e427d5ed5720/sys/contrib/openzfs/cmd/zpool/zpool_main.c#L3492

[fichtner]

Thanks for looking into this. Feel free to provide a PR, but I won't be able to review and commit in the next two weeks.

[fichtner]

(I'd say that ZPOOL_IMPORT_PATH might be the better path forward as I've avoided -c in the past for portability.)

[nt1]

I'll open a PR to fix this this evening. I can work around this issue for now, so no rush on the review.

[nt1]

I will propose a change that imports pools from zpool cache at boot (just like vanilla FreeBSD) rather than allowing the implementation of zpool import to dictate what's imported.

Pros of using zpool cache

1. It's explicit, fstab like behavior.
2. Consistency across reboots, the system boots with the same pools it had at shutdown.
3. Prevents importing potentially problematic pools that are connected to the system, but have never been successfully imported.
4. On appliances, may help deter/prevent tampering with root fs.

Cons of using zpool cache

1. The existence and purpose of zpool cache does not appear to be widely known or extensively documented. This may surprise some people.
2. Boot behavior is changing. The end user may see a change in available pools after booting this release (easily resolved by importing missing pools and exporting those that shouldn't be there).
3. The cache file should be present in every existing install. If, for any reason, the cache file is missing, the system will not boot properly.
4. The path of the cachefile could change in future FreeBSD/OpenZFS releases (which would require a fix to rc).