[systemd-devel] fsck, /home, btrfs, multiple partitions/drives, boot failure [Ubuntu 15.04]

[Roger Binns]

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My immediate problem is a boot failure with systemd on Ubuntu 15.04
because of fsck issues (systemd timing out fscking something it
shouldn't).  Prior Ubuntu releases and upstart work just fine.  Martin
Pitt @ Ubuntu said I should bring the issue here in the Ubuntu bug report:

  https://bugs.launchpad.net/ubuntu/+source/systemd/+bug/1447879

I have 6 drives in my system.  Two identical 960GB SSDs (model,
firmware etc all the same, only serial number difference), another two
identical 256GB SSDs (same story), and two spinning drives.

Of note is that my root and /home are both btrfs subvolumes of a RAID0
btrfs using the two first SSDs.  /etc/fstab has these two lines for
them (wrapped by email client):

UUID=3ff68715-0daa-4e44-8de2-0997f36d8ab6 / btrfs
defaults,autodefrag,compress=lzo,subvol=@ 0 1

UUID=3ff68715-0daa-4e44-8de2-0997f36d8ab6 /home btrfs
defaults,autodefrag,compress=lzo,subvol=@home 0 2

blkid output mentioning that UUID:

/dev/sda1: LABEL="main" UUID="3ff68715-0daa-4e44-8de2-0997f36d8ab6"
UUID_SUB="12243c27-9502-4a1e-b1d1-d1998107b9e4" TYPE="btrfs"
PARTUUID="011a8e03-01"

/dev/sdb1: LABEL="main" UUID="3ff68715-0daa-4e44-8de2-0997f36d8ab6"
UUID_SUB="abda2c4f-3346-44e5-b32e-7c1bba0ba728" TYPE="btrfs"
PARTUUID="1537012a-01"

What happens is that / is mounted successfully, as are all the other
filesystems that aren't /home or mounted below /home.

There will be a message about waiting for fsck either including the
UUID above, or CT960M500SSD1 (drive id), and after 1m30s it times out
and dumps me in a root shell.

The devices/partitions are already mounted as root, so no amount of
further checking makes sense.  If it just went ahead and mounted the
@home subvolume it would be fine.  Instead systemd is unhelpfully
timing out, without any diagnostics as to why it is trying this and
why it doesn't succeed.

Note that /sbin/fsck.btrfs is a shell script (Suse/SGI copyright) that
just prints out "BTRFS file system" if the device node exists - and
doesn't do anything else.

The Ubuntu bug report includes numerous attachments with various
systemctl and similar outputs, full /etc/fstab etc.  I'll happily
capture whatever else can help diagnose and fix this problem.

Roger
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