Docker 1.6.0 on RHEL 6.5 with SELinux, can’t run containers without root

dockerrhel6selinux

I'm trying to run a container on a RHEL 6.5 but I keep hitting this problem:

sudo docker run -u postgres -it registry/postgres /bin/bash
/bin/bash: error while loading shared libraries: libtinfo.so.5: cannot open shared object file: Permission denied

When run as user 'root', the container starts fine but the problem appears again when trying to switch to another user:

$ sudo docker run -u root -it registry/database /bin/bash
[root@8a20410eaa5e /]# su postgres
su: /bin/bash: Permission denied

This is a specific container built by us, based on CentOS 6.5 an that runs Postgres. The Dockerfile to build it has "USER postgres" in it, and it works fine elsewhere except these servers. I can reproduce the same behaviour with a busybox container:

$ sudo docker run -u nobody -it 10.188.13.136:8080/busybox
/ $ ls
/bin/sh: ls: Permission denied

The RHEL 6.5 host has SELinux enabled. We have other other hosts where SELinux and this container works fine there. The audit log for this host looks clean, no error messages that I can see when trying to run the container.

This is what we've tried so far:

  • update the SELinux policies in RHEL ("sudo yum upgrade selinux-policy"), as they were not the latest versions
  • get SELinux into permissive mode (setenforce 0); not tried to switch it off completely and reboot
  • start the Docker daemon with "–selinux-enabled=true"
  • start the container with –privileged
  • start the container with –security-opt=:label:disable
  • we're running the latest RHEL 6.5 kernel: 2.6.32-504.16.2.el6.x86_64

Also run a strace session for the 'su ' command within the container but could not see much beyond these:

 17    setgid(10000)                     = 0
 17    setuid(10000)                     = 0
 17    munmap(0x7f07a3540000, 2101304)   = 0
 17    munmap(0x7f07a311c000, 2113776)   = 0
 17    munmap(0x7f07a2f03000, 2196352)   = 0
 17    munmap(0x7f07a2cea000, 2198192)   = 0
 17    munmap(0x7f07a2ae8000, 2101272)   = 0
 17    munmap(0x7f07a28e4000, 2109624)   = 0
 17    munmap(0x7f07a26e0000, 2109672)   = 0
 17    munmap(0x7f07a24d3000, 2148896)   = 0
 17    munmap(0x7f07a22d0000, 2105488)   = 0
 17    munmap(0x7f07a20cb000, 2113848)   = 0
 17    munmap(0x7f07a1ec5000, 2118168)   = 0
 17    munmap(0x7f07a3321000, 2221912)   = 0
 17    execve("/bin/bash", ["bash"], [/* 15 vars */]) = -1 EACCES (Permission denied)
 17    write(2, "su: ", 4)               = 4
 17    write(2, "/bin/bash", 9)          = 9

The full strace dump is here in case it's needed: http://pastebin.com/42C2B8LP.

We're not sure what to look for next, any ideas?

Best Answer

I was finally able to solve this problem. Which means that it seems that I found a solution, but I'm not still sure what the problem is:

1) pull container from registry 2.0 + run with docker 1.6 -> fail

2) pull container from registry 0.9.x (either Docker's own or the Artifactory server that we run internally) + run with docker 1.6 -> works

3) pull container from registry 2.0 + run with docker 1.5 or older -> fail

4) pull container form registry 0.9.x + run with docker 1.5 or newer -> works

I don't really think that Registry 2.0 is at fault but I have no better answer. The new registry is much faster than the old one but guess we'll stick with the older registry for the time being.

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