loader: Add support for booting from a ZFS snapshot
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Authored by allanjude on Feb 15 2023, 1:59 AM.

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manu
tsoome
rew
imp

Group Reviewers

Klara

Commits

rGa849842f510a: loader: Add support for booting from a ZFS snapshot

Summary

When booting from a snapshot we need to follow a different code path
to turn the objset ID into the name, and for forward lookups we need
to walk the parent's snapnames_zap.

With this, it is possible to set the pools BOOTFS property to a
snapshot and boot with a read-only filesystem of that snapshot.

Sponsored By: Beckhoff Automation GmbH & Co. KG
Sponsored By: Klara, Inc.

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rG FreeBSD src repository

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Buildable 49934
Build 46826: arc lint + arc unit

Event Timeline

allanjude created this revision.Feb 15 2023, 1:59 AM

Herald added a reviewer: manu. · View Herald TranscriptFeb 15 2023, 1:59 AM

Herald added subscribers: dab, delphij, imp. · View Herald Transcript

allanjude added reviewers: tsoome, rew, Klara, imp.Feb 15 2023, 2:00 AM

Harbormaster returned this revision to the author for changes because remote builds failed.Feb 15 2023, 2:00 AM

Harbormaster failed remote builds in B49792: Diff 117273!

jlduran_gmail.com added a subscriber: jlduran_gmail.com.Feb 15 2023, 2:07 AM

val_packett.cool added a subscriber: val_packett.cool.Feb 19 2023, 5:13 PM

lwhsu added a subscriber: lwhsu.Feb 20 2023, 10:51 PM

Rebase

allanjude requested review of this revision.Feb 21 2023, 9:44 PM

Harbormaster completed remote builds in B49934: Diff 117713.Feb 21 2023, 9:44 PM

so can we use zfs:<snapshot> in all the places where we can use zfs:<dataset> now with these changes?

btw, this looks really cool...

One other thing... where is the 'read only' flag set. I may be missing it, but I don't see it here.

In D38600#881029, @imp wrote:

so can we use zfs:<snapshot> in all the places where we can use zfs:<dataset> now with these changes?

yes, you can use a snapshot for currdev etc.

You can use it with zpool set bootfs=<snapshot> pool

In D38600#881030, @imp wrote:

btw, this looks really cool...

One other thing... where is the 'read only' flag set. I may be missing it, but I don't see it here.

Like a CDROM, the snapshot is just always read-only, it didn't require setting any other flags. Every filesystem is read-only until we remount root r/w later in the boot process.

tsoome accepted this revision.Feb 21 2023, 10:39 PM

This revision is now accepted and ready to land.Feb 21 2023, 10:39 PM

Tested - works as expected for me,

Closed by commit rGa849842f510a: loader: Add support for booting from a ZFS snapshot (authored by allanjude). · Explain WhyMar 14 2023, 2:20 PM

This revision was automatically updated to reflect the committed changes.

allanjude added a commit: rGa849842f510a: loader: Add support for booting from a ZFS snapshot.