[lxc-users] container complains about "too many levels of symbolic links"

[André Janowicz]

You were right, that was the problem. I think I'll get rid of autofs on
our servers..

Thank you very much!

On 21.07.2015 18:26, Michael H. Warfield wrote:
> On Tue, 2015-07-21 at 13:20 +0200, André Janowicz wrote:
>> Hello,
>>
>> does anybody know why my containers complain once per
>> "lxc.mount.entry"  about  "too many levels of symbolic links"  and
>> refuse to start, but then run fine on the  #mountpoints + 1st
>> attempt?
>> I asked this exact question two weeks ago at stackoverflow in more
>> detail but got no answers.  Here's my post:
>>
>> http://stackoverflow.com/questions/31266838/why-does-lxc-fail-to-start-because-of-too-many-levels-of-symbolic-links-but-do
>> I'm running Ubuntu 14.04 LTS with LXC 1.07 and I'd like to access
>> directories from within my lxc-container (ubuntu template) which are
>> NFS mounts managed by autofs on the host. 
>>
>> Lets say the host has 3 different NFS-shares mounted by autofs:
>>
>> auto.vol:
>>
>> /vol/server1 -fstype=nfs IPserver1:/vol/server1
>> /vol/server2 -fstype=nfs IPserver2:/vol/server2
>> /vol/server3 -fstype=nfs IPserver3:/vol/server3
>>
>> Now I try to access these from within my container, config looks like
>> this:
>>
>> lxc.mount.entry = /vol/server1     vol/server1 none bind 0 0
>> lxc.mount.entry = /vol/server2     vol/server2 none bind 0 0
>> lxc.mount.entry = /vol/server3     vol/server3 none bind 0 0
>>
>> Now the problem is this does only work the second or third time I
>> start the container, most of the time LXC complains about 'Too many
>> levels of symbolic links' and quits. This is the output:
>>
>> lxc-start: conf.c: mount_entry: 2049 Too many levels of symbolic links - failed to mount '/vol/server1' on '/usr/lib/x86_64-linux-gnu/lxc/vol/server1'
>> lxc-start: conf.c: lxc_setup: 4163 failed to setup the mount entries for 'vm.local'
>> lxc-start: start.c: do_start: 688 failed to setup the container
>> lxc-start: sync.c: __sync_wait: 51 invalid sequence number 1. expected 2
>>
>> The second time I start the container it complains about /vol/server2
>> and so on until it finally works as expected.
>>
>> what is the problem and why does it work as I start it more often?
> It seems to me (and I use autofs extensively) that you're running into a
> race condition with autofs automounting the file systems you want lxc to
> then bind mount and they're not coming ready in time.  The reason it
> will have worked the second time is that autofs will have had sufficient
> time automount the first file system and it's then there but then the
> next one isn't so you restart the whole process over again.
>
> Little experiment to try...  For your example above...  Before starting
> the container, try this...
>
> ls /vol/server1 /vol/server2 /vol/server3
>
> When that completes, the three file systems will have been automounted
> by autofs.  Then immediately start your container.  My guess is that it
> will start without a problem.  That would indicate that it is a race
> where the bind mounts in lxc are getting ahead of the automounts in
> autofs.
>
> I don't know what your trying to accomplish by going through autofs this
> way.  Once the container is up, the bind mounts are going to lock autofs
> into keeping those file systems mounted.  Wouldn't it make more sense to
> just hard mount them before starting the containers?  You would
> eliminate autofs periodially checking the mount points to see if they
> could be unmounted.  I just don't see what benefit you're deriving from
> having autofs in the loop here.
>
> The race condition may be a quirk in the way the bind mounts are
> executed by lxc in setting up the container.  If the "ls" hack works,
> you could automate this in one of the hook scripts to get the autofs
> file systems premounted.
>
>> Thanks in advance,
>>
>>
>> André
>>
>>
>>
>>
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-- 
André Janowicz, B.Sc.
Systemadministrator
Lehrstuhl für Genominformatik
Universität Duisburg-Essen
Virchowstr. 183
45147 Essen, Germany
Tel.+49 201 723-4045

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