[lxc-users] How to control order of bind mounts?

[Ben Warren]

Hi,

I have a container with two overlapping bind mounts.  I’m seeing that the order in which they are applied does not seem to be consistent.

Here’s a dump of the commands used:

# Create a container from local image
/usr/bin/lxc init local:c1 c1
# Add four bind mounts
/usr/bin/lxc config device add c1 build disk source=/home/ben/src path=/src
/usr/bin/lxc config device add c1 bincd disk source=/home/ben/src/sc/bin-cd path=/src/sc/bin
/usr/bin/lxc config device add c1 pkgcd disk source=/home/ben/src/sc/pkg-cd path=/src/sc/pkg
/usr/bin/lxc config device add c1 home disk source=/home/ben path=/home/ben
#set a bunch of config
/usr/bin/lxc config set c1 environment.PATH /usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:/usr/local/go/bin:/src/sc/bin
/usr/bin/lxc config set c1 environment.GOPATH /src/sc
/usr/bin/lxc config set c1 environment.SC_HOSTNAME localhost
/usr/bin/lxc config set c1 environment.WORKSPACE /
/usr/bin/lxc config set c1 environment.PYTHONPATH /src/sc/src
/usr/bin/lxc config set c1 raw.idmap "both 1001 0"
/usr/bin/lxc config set c1 raw.lxc lxc.aa_profile=unconfined
/usr/bin/lxc config device add c1 loop0 unix-block path=/dev/loop0
/usr/bin/lxc config device add c1 loop1 unix-block path=/dev/loop1
/usr/bin/lxc config device add c1 loop2 unix-block path=/dev/loop2
/usr/bin/lxc config device add c1 loop3 unix-block path=/dev/loop3
/usr/bin/lxc config device add c1 loop4 unix-block path=/dev/loop4
/usr/bin/lxc config device add c1 loop5 unix-block path=/dev/loop5
/usr/bin/lxc config device add c1 loop6 unix-block path=/dev/loop6
/usr/bin/lxc config device add c1 loop7 unix-block path=/dev/loop7
/usr/bin/lxc config device add c1 loop-control unix-char path=/dev/loop-control
# Start the container
/usr/bin/lxc start c1

What I see is that sometimes (but not always) the “build” mount overlaps the “bincd” mount, instead of the other way around.  Note that these mounts are configured before the container is started.  Is it better to start the container first, or is there a way to specify deterministically which order the bind mounts will be applied?

Version info:

ben at skycontrol:~$ lxc --version
2.0.10
ben at skycontrol:~$ cat /etc/lsb-release 
DISTRIB_ID=Ubuntu
DISTRIB_RELEASE=16.04
DISTRIB_CODENAME=xenial
DISTRIB_DESCRIPTION="Ubuntu 16.04.1 LTS”

thanks,
Ben


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