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Description of problem:

Running domainname in unprivileged container fails with

domainname: you must be root to change the domain name

Version-Release number of selected component (if applicable):

docker-1.2.0-1.5.el7.x86_64 on the host

How reproducible:

Deterministic

Steps to Reproduce:
1. docker run -ti rhel7 bash -c 'yum install -y hostname ; domainname example.test'
2. echo $?

Actual results:

# docker run -ti rhel7 bash -c 'yum install -y hostname ; domainname example.test'
rhel-7-server-rpms                                      | 3.7 kB  00:00:00     
rhel-7-server-rpms/7Server/x86_64/primary_db            | 6.7 MB  00:00:02     
[...]
Complete!
domainname: you must be root to change the domain name
# echo $?
1
#

Expected results:

# docker run -ti rhel7 bash -c 'yum install -y hostname ; domainname example.test'
rhel-7-server-rpms                                      | 3.7 kB  00:00:00     
rhel-7-server-rpms/7Server/x86_64/primary_db            | 6.7 MB  00:00:02     
[...]
Complete!
# echo $?
0
#

Additional info:

Strace shows

brk(0)                                  = 0xd4b000
setdomainname("example.test", 12)       = -1 EPERM (Operation not permitted)
write(2, "domainname: ", 12domainname: )            = 12
write(2, "you must be root to change the d"..., 42you must be root to change the domain name) = 42

This is not a bug.  You are not allowed to change the domainname or hostname from within a container.

(In reply to Daniel Walsh from comment #3)
> This is not a bug.  You are not allowed to change the domainname or hostname
> from within a container.

Does it apply to the NIS/YP domain name as well? That's what domainname changes. It's not dealing with DNS hostname/domain name.

Yes, you would need to set these domains outside of the container, in the docker command. Or run with the sys_admin or maybe net_admin capability.