lxc-update-config for Ubuntu 18.04

[der.hans]

moin moin,

lxc wins this month's award for hidden requirements.

Ubuntu 18.04 moved to lxc 3.x where some deprecated options are no longer
allowed. They've mostly been renamed.

I've been using lxc on Ubuntu and debian for a couple of years and never
ran into any news about deprecation, much less that they would stop
working. Surprise.

The error message is less than useful as it says that the required option
listed in all of the resources I was reading is unknown.

----
lxc-ls: confile.c: parse_line: 2340 Unknown configuration key "lxc.id_map"
lxc-ls: parse.c: lxc_file_for_each_line_mmap: 102 Failed to parse config:
lxc.id_map = u 0 100000 65536
Failed to load config for fred
----

Yeah, that error is helpful and tells me how to fix the known issue...

Running lxc-update-config on the config file for each container seems to
fix the issue. Probably need to update general configs as well for new
containers.

Also, lxc-templates was uninstalled during the upgrade, but lxc complains
and fails if the templates from that package are missing.

https://github.com/lxc/lxd/issues/4396#issuecomment-378322166

Note that the [i] listed for the networking options appears to mean the
interface number. 0 works for my configs.

OK, time to clean up all this yak fur and try to remember what I was
actually trying to accomplish :).

ciao,

der.hans
-- 
#  https://www.LuftHans.com   https://www.PhxLinux.org
#  "If it's not a toy you're looking at it wrong." -- der.hans