From 18d0d68e4e4fbca95e738c8e5405902f405797f2 Mon Sep 17 00:00:00 2001 From: Stoiko Ivanov Date: Wed, 31 Mar 2021 11:52:04 +0200 Subject: [PATCH] zfs: add section on zpool-features primarily in order to warn users booting from ZFS with grub. Signed-off-by: Stoiko Ivanov Reviewed-By: Aaron Lauterer Signed-off-by: Thomas Lamprecht --- local-zfs.adoc | 35 +++++++++++++++++++++++++++++++++++ 1 file changed, 35 insertions(+) diff --git a/local-zfs.adoc b/local-zfs.adoc index 4819678..5433c4f 100644 --- a/local-zfs.adoc +++ b/local-zfs.adoc @@ -699,3 +699,38 @@ in the pool will opt in for small file blocks). ---- # zfs set special_small_blocks=0 / ---- + +[[sysadmin_zfs_features]] +ZFS Pool Features +~~~~~~~~~~~~~~~~~ + +Changes to the on-disk format in ZFS are only made between major version changes +and are specified through *features*. All features, as well as the general +mechanism are well documented in the `zpool-features(5)` manpage. + +Since enabling new features can render a pool not importable by an older version +of ZFS, this needs to be done actively by the administrator, by running +`zpool upgrade` on the pool (see the `zpool-upgrade(8)` manpage). + +Unless you need to use one of the new features, there is no upside to enabling +them. + +In fact, there are some downsides to enabling new features: + +* A system with root on ZFS, that still boots using `grub` will become + unbootable if a new feature is active on the rpool, due to the incompatible + implementation of ZFS in grub. +* The system will not be able to import any upgraded pool when booted with an + older kernel, which still ships with the old ZFS modules. +* Booting an older {pve} ISO to repair a non-booting system will likewise not + work. + +IMPORTANT: Do not upgrade your rpool if your system is still booted with `grub`, +as this will render your system unbootable. This includes systems installed +before {pve} 5.4, and systems booting with legacy BIOS boot (see +xref:sysboot_determine_bootloader_used[how to determine the bootloader]). + +.Enable new features for a pool: +---- +# zpool upgrade +----