[lxc-users] lxd-agent and Snap package

[David Lakatos]

Hi LXC community,

I read about the situation on multiple forums that CentOS 7 and CentOS 8
LXD VM images currently cannot start the lxd-agent.service due to a
possible CentOS kernel bug. It seems that I hit the same issue, but found
something really strange in the meantime, which I could not explain. Please
help me out if you have any idea why there is a difference between the two
scenarios' results:

# id
uid=0(root) gid=0(root) groups=0(root)
# uname -a
Linux dlakatos847-laptop 5.9.10-1-default #1 SMP Mon Nov 23 09:08:45 UTC
2020 (b7c3768) x86_64 x86_64 x86_64 GNU/Linux

Scenario A: I use OpenSuSE Tumbleweed OSS repo's LXD package:

   1. # zypper in -y lxd
   ...
   Checking for file conflicts:
   ...................................................................................................................[done]
   (1/2) Installing: lxd-4.8-1.1.x86_64
   ...........................................................................................................[done]
   (2/2) Installing: lxd-bash-completion-4.8-1.1.noarch
   ...........................................................................................[done]
   2. # systemctl start lxd.service
   3. # /usr/bin/lxc version
   Client version: 4.8
   Server version: 4.8
   4. # /usr/bin/lxd init
   ...
   5. # /usr/bin/lxc launch images:centos/7/amd64 centos --vm
   Creating centos
   Starting centos
   6. # /usr/bin/lxc ls

   +--------+---------+-----------------------+-----------------------------------------------+-----------------+-----------+
   | NAME   |  STATE  |         IPV4          |                     IPV6
                      |      TYPE       | SNAPSHOTS |

   +--------+---------+-----------------------+-----------------------------------------------+-----------------+-----------+
   | centos | RUNNING | 10.137.136.143 (eth0) |
   fd42:3542:bbfa:726c:216:3eff:fe5f:670b (eth0) | VIRTUAL-MACHINE | 0
   |

   +--------+---------+-----------------------+-----------------------------------------------+-----------------+-----------+
   7. # /usr/bin/lxc exec centos bash
   *Error: Failed to connect to lxd-agent*

I checked, the lxd-agent.service could not start, looks like the same issue
as explained by Stéphane:
https://lists.linuxcontainers.org/pipermail/lxc-users/2020-October/015342.html

Scenario B: I use the Snap package:

   1. # snap install lxd
   lxd 4.8 from Canonical* installed
   2. # /snap/bin/lxc version
   Client version: 4.8
   Server version: 4.8
   3. # /snap/bin/lxd init
   ... (use the same bridge lxdbr0) ...
   4. # /snap/bin/lxc launch images:centos/7/amd64 centos --vm
   Creating centos
   Starting centos
   5. # /snap/bin/lxc ls

   +--------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
   |  NAME  |  STATE  |         IPV4         |                     IPV6
                    |      TYPE       | SNAPSHOTS |

   +--------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
   | centos | RUNNING | 10.137.136.89 (eth0) |
   fd42:3542:bbfa:726c:216:3eff:fe78:dc48 (eth0) | VIRTUAL-MACHINE | 0
   |

   +--------+---------+----------------------+-----------------------------------------------+-----------------+-----------+
   6. # /snap/bin/lxc exec centos bash
   *[root at localhost ~]#*

If the lxd-agent.service issue really is a CentOS bug, why does it matter
if I use my distro's LXD or the Snap package? Why is it working, when I use
the Snap package?

Thank you,
David Lakatos
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