"lxc-create -B best" fails on non-btrfs/zfs system

[Martin Pitt]

As per documentation, the `-B best` option should automatically select the best backingstore, falling back all the way to dir.

But apparently it doesn't, at least not in artful's 2.1.0-0ubuntu1:

$ sudo lxc-create -B best --name=autopkgtest-xenial -t ubuntu -- -r xenial
lxc-create: autopkgtest-xenial: storage/btrfs.c: btrfs_create: 860 Inappropriate ioctl for device - Failed to create btrfs subvolume "/var/lib/lxc/autopkgtest-xenial/rootfs"
lxc-create: autopkgtest-xenial: storage/zfs.c: zfs_create: 758 Failed to create zfs dataset "zfs:lxc/autopkgtest-xenial": lxc-create: autopkgtest-xenial: utils.c: run_command: 2326 failed to exec command
lxc-create: autopkgtest-xenial: storage/zfs.c: zfs_mount: 256 No such file or directory - Failed to mount "lxc/autopkgtest-xenial" on "/usr/lib/x86_64-linux-gnu/lxc"
lxc-create: autopkgtest-xenial: lxccontainer.c: create_run_template: 1294 Failed to mount rootfs
lxc-create: autopkgtest-xenial: lxccontainer.c: create_run_template: 1473 container creation template for autopkgtest-xenial failed
lxc-create: autopkgtest-xenial: storage/zfs.c: zfs_destroy: 613 Failed to detect zfs dataset "lxc/autopkgtest-xenial": lxc-create: autopkgtest-xenial:
lxc-create: autopkgtest-xenial: lxccontainer.c: container_destroy: 2653 Error destroying rootfs for autopkgtest-xenial
lxc-create: autopkgtest-xenial: tools/lxc_create.c: main: 326 Error creating container autopkgtest-xenial

Moreover, it creates cruft which is hard to clean up again:

$ sudo lxc-ls -f
NAME STATE AUTOSTART GROUPS IPV4 IPV6
autopkgtest-xenial STOPPED 0 - - -

$ sudo lxc-destroy -n autopkgtest-xenial
lxc-destroy: autopkgtest-xenial: storage/zfs.c: zfs_destroy: 613 Failed to detect zfs dataset "lxc/autopkgtest-xenial": lxc-destroy: autopkgtest-xenial: utils.c: run_command: 2326 failed to exec command
lxc-destroy: autopkgtest-xenial: lxccontainer.c: container_destroy: 2653 Error destroying rootfs for autopkgtest-xenial
Destroying autopkgtest-xenial failed

$ sudo ls -lR /var/lib/lxc/autopkgtest-xenial
/var/lib/lxc/autopkgtest-xenial:
total 8
-rw-r--r-- 1 root root 149 Feb 20 20:41 config
drwxr-xr-x 2 root root 4096 Feb 20 20:41 rootfs

/var/lib/lxc/autopkgtest-xenial/rootfs:
total 0

This can only be cleaned up with `sudo rm -r`.

autopkgtest-build-lxc uses this option to get performant containers out of the box. Arguably `-B best` is a sort of "unbreak my containers" option and should always implicitly be used, but is there something else that I should do here?

ProblemType: Bug
DistroRelease: Ubuntu 17.10
Package: lxc 2.1.0-0ubuntu1
ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13
Uname: Linux 4.13.0-32-generic x86_64
NonfreeKernelModules: zfs zunicode zavl zcommon znvpair
ApportVersion: 2.20.7-0ubuntu3.7
Architecture: amd64
Date: Tue Feb 20 20:38:55 2018
JournalErrors:
 Error: command ['journalctl', '-b', '--priority=warning', '--lines=1000'] failed with exit code 1: Hint: You are currently not seeing messages from other users and the system.
       Users in the 'systemd-journal' group can see all messages. Pass -q to
       turn off this notice.
 No journal files were opened due to insufficient permissions.
PackageArchitecture: all
SourcePackage: lxc
UpgradeStatus: No upgrade log present (probably fresh install)
defaults.conf:
 lxc.net.0.type = veth
 lxc.net.0.link = lxcbr0
 lxc.net.0.flags = up
 lxc.net.0.hwaddr = 00:16:3e:xx:xx:xx
lxcsyslog:

[Christian Brauner (cbrauner)]

On Tue, Feb 20, 2018 at 08:43:41PM -0000, Martin Pitt wrote:
> Public bug reported:
>
> As per documentation, the `-B best` option should automatically select
> the best backingstore, falling back all the way to dir.
>
> But apparently it doesn't, at least not in artful's 2.1.0-0ubuntu1:

Hm, is it possible for you to try and reproduce with current master.
Works fine for me:

chb@conventiont|~
> sudo lxc-create -B best --name=autopkgtest-xenial -t ubuntu -- -r xenial
lxc-create: autopkgtest-xenial: storage/btrfs.c: btrfs_create: 861 Inappropriate ioctl for device - Failed to create btrfs subvolume "/var/lib/lxc/autopkgtest-xenial/rootfs"
lxc-create: autopkgtest-xenial: storage/zfs.c: zfs_create: 762 Failed to create zfs dataset "zfs:default/lxc/autopkgtest-xenial": The ZFS modules are not loaded.
Try running '/sbin/modprobe zfs' as root to load them.
lxc-create: autopkgtest-xenial: storage/lvm.c: do_lvm_create: 183 Failed to create logical volume "autopkgtest-xenial": Volume group "lvm_img" not found
lxc-create: autopkgtest-xenial: storage/lvm.c: lvm_create: 655 Error creating new logical volume "lvm:/dev/lvm_img/autopkgtest-xenial" of size "1073741824 bytes"
Checking cache download in /var/cache/lxc/xenial/rootfs-amd64 ...
Installing packages in template: apt-transport-https,ssh,vim,language-pack-en
Downloading ubuntu xenial minimal ...
W: Target architecture is the same as host architecture; disabling QEMU support
I: Running command: debootstrap --arch amd64 --verbose --components=main,universe --include=apt-transport-https,ssh,vim,language-pack-en xenial /var/cache/lxc/xenial/partial-amd64 http://archive.ubuntu.com/ubuntu
I: Retrieving InRelease
I: Checking Release signature
I: Valid Release signature (key id 790BC7277767219C42C86F933B4FE6ACC0B21F32)
I: Retrieving Packages
I: Validating Packages
I: Retrieving Packages