"File exists" error while starting container

[Systems Administration]

On a freshly installed Ubuntu 20.04.1 VM, while starting a container created using

sudo lxc-create -t ubuntu -n testlxc

the following messages are shown:

lxc-start: testlxc: cgroups/cgfsng.c: mkdir_eexist_on_last: 1143 File exists - Failed to create directory "/sys/fs/cgroup/cpuset//lxc.monitor.testlxc"
lxc-start: testlxc: conf.c: lxc_setup_boot_id: 3249 Permission denied - Failed to mount /dev/.lxc-boot-id to /proc/sys/kernel/random/boot_id

The container starts correctly but it would be nice find out why those errors are being issued.

lxc-checkconfig output follows:

Kernel configuration not found at /proc/config.gz; searching...
Kernel configuration found at /boot/config-5.4.0-42-generic
--- Namespaces ---
Namespaces: enabled
Utsname namespace: enabled
Ipc namespace: enabled
Pid namespace: enabled
User namespace: enabled
Network namespace: enabled

--- Control groups ---
Cgroups: enabled

Cgroup v1 mount points:
/sys/fs/cgroup/systemd
/sys/fs/cgroup/hugetlb
/sys/fs/cgroup/cpuset
/sys/fs/cgroup/memory
/sys/fs/cgroup/cpu,cpuacct
/sys/fs/cgroup/net_cls,net_prio
/sys/fs/cgroup/blkio
/sys/fs/cgroup/perf_event
/sys/fs/cgroup/pids
/sys/fs/cgroup/freezer
/sys/fs/cgroup/devices
/sys/fs/cgroup/rdma

Cgroup v2 mount points:
/sys/fs/cgroup/unified

Cgroup v1 clone_children flag: enabled
Cgroup device: enabled
Cgroup sched: enabled
Cgroup cpu account: enabled
Cgroup memory controller: enabled
Cgroup cpuset: enabled

--- Misc ---
Veth pair device: enabled, loaded
Macvlan: enabled, not loaded
Vlan: enabled, not loaded
Bridges: enabled, loaded
Advanced netfilter: enabled, not loaded
CONFIG_NF_NAT_IPV4: missing
CONFIG_NF_NAT_IPV6: missing
CONFIG_IP_NF_TARGET_MASQUERADE: enabled, not loaded
CONFIG_IP6_NF_TARGET_MASQUERADE: enabled, not loaded
CONFIG_NETFILTER_XT_TARGET_CHECKSUM: enabled, loaded
CONFIG_NETFILTER_XT_MATCH_COMMENT: enabled, not loaded
FUSE (for use with lxcfs): enabled, not loaded

--- Checkpoint/Restore ---
checkpoint restore: enabled
CONFIG_FHANDLE: enabled
CONFIG_EVENTFD: enabled
CONFIG_EPOLL: enabled
CONFIG_UNIX_DIAG: enabled
CONFIG_INET_DIAG: enabled
CONFIG_PACKET_DIAG: enabled
CONFIG_NETLINK_DIAG: enabled
File capabilities:

Note : Before booting a new kernel, you can check its configuration
usage : CONFIG=/path/to/config /usr/bin/lxc-checkconfig

[Stéphane Graber (stgraber)]

The cpuset "error" is normal, it just means the directory was already there and is getting recycled. The boot_id permission problem has already been fixed upstream.

[Launchpad Janitor (janitor)]

This bug was fixed in the package lxc - 1:4.0.12-0ubuntu1

---------------
lxc (1:4.0.12-0ubuntu1) jammy; urgency=medium

  * Cherry-pick upstream bugfixes (stable-4.0):
    - 0002-lxc-checkconfig-Fix-bashism.patch
    - 0003-doc-Fix-reverse-allowlist-denylist.patch (LP: #1957934)

  * New upstream bugfix release (4.0.12):
    (https://discuss.linuxcontainers.org/t/lxc-4-0-12-has-been-released/13288)
    - Fixed CRIU restoration of containers with pre-created veth interfaces
    - Fixed issue with kernels lacking SMT support
    - Extended cgroup2 config options in lxc.mount.auto (cgroup2)
    - lxc-download now relies on HTTPS for validation (avoids GPG issues)

  * New upstream bugfix release (4.0.11)
    (LP: #1943441, LP: #1938771, LP: #1891903):
    (https://discuss.linuxcontainers.org/t/lxc-4-0-11-has-been-released/12427)
    - Core scheduling support (lxc.sched.core)
    - riscv64 support in lxc.arch
    - Significantly improved bash completion profile
    - Greater use of the new VFS mount API (when supported by the kernel)
    - Fix containers with empty network namespaces
    - Handle kernels that lack TIOCGPTPEER
    - Improve CPU bitmask/id handling (handle skipped CPU numbers)
    - Reworked the tests to run offline

  * Bump to debhelper 12 (allows focal SRUs)
  * Bump standards to 4.6.0.1
  * Add lintian overrides for incorrect bashism detection
  * Remove bash completion install logic (now done upstream)

 -- Stéphane Graber <email address hidden> Wed, 02 Feb 2022 20:48:39 -0500