Re: [PATCH v2 3/3] mkdumprd: append "x-initrd.mount" to the mount options.

Now when mount in /etc/fstab fails, systemd would not consider it as critical and it would continue to boot. In fact, emergency service is triggered, but not in a isolation mode, and it results in the emergency service getting shutdown at some point later of the boot process. We need isolation otherwise we won't see any emergency service. That is because in kdump initramfs, mount units specified in /etc/fstab are required by "local-fs.target". When any of these mounts fails, local-fs.target fails. For kdump initramfs, we need to isolate to emergency service on any of the mount failure, that said, every service should be stopped and onlu emergency service would run. But local-fs.target won't trigger that on its failure. That means in case of mount failure, local-fs.target also enters failure state, but all the service will continue without any interruption. After digging looking into source code of systemd-fstab-generator. I find "x-initrd.mount" using in initramfs mount, will make the mount units required by "initrd-root-fs.target" rather than it's used to be "local-fs.target". "initrd-root-fs.target" is suitable to us because if it fails, it will isolate to emergency service. That means in case of any mount failure, the emergeny service will start and everything else will stop. We want this effect because we need to take kdump fail-safe action when there's a mount failure. From systemd unit point of view, "initrd-root-fs.target" has OnFailureIsolate=yes, but "local-fs.target" doesn't. From systemd.unit(5): OnFailureIsolate= Takes a boolean argument. If true, the unit listed in OnFailure= will be enqueued in isolation mode, i.e. all units that are not its dependency will be stopped. If this is set, only a single unit may be listed in OnFailure=. Defaults to false. NOTE: Harald who contributed "x-initrd.mount" in systemd, confirmed that this feature will stay. Signed-off-by: WANG Chao <chaowang(a)redhat.com&gt; --- mkdumprd | 11 +++++++++++ 1 file changed, 11 insertions(+) diff --git a/mkdumprd b/mkdumprd index ba35800..5d12a82 100644 --- a/mkdumprd +++ b/mkdumprd @@ -106,6 +106,17 @@ to_mount() { _fstype=$(findmnt -k -f -n -r -o FSTYPE $_dev) _options=$(findmnt -k -f -n -r -o OPTIONS $_dev) _options=${_options/#ro/rw} #mount fs target as rw in 2nd kernel + # "x-initrd.mount" mount failure will trigger isolate emergency service + # W/o this, systemd won't isolate, thus we won't get to emergency. + # This is not applicable to remote fs mount, because if we use + # "x-initrd.mount", remote mount will become required by + # "initrd-root-fs.target", instead of "remote-fs.target". That's how it is + # handled within systemd internal. We need remote mount to be required + # "remote-fs.target", because we need to bring up network before any remote + # mount and "remote-fs.target" can be a checkpoint of that.