Rudder

On Docker /etc/hosts is a bind-mounted file, which cannot be moved, just edited.

root@rts_m01_r01:/# cat /proc/mounts  | grep hosts
/dev/sdb /etc/hosts btrfs rw,noatime,space_cache,subvolid=5,subvol=/containers/df161786fd391f3afd72e7f671dad354ae0bae730261b80b79ebbc50b6fcd737/hosts 0 0
root@rts_m01_r01:/#

This causes a promise to fail:

2016-03-18T00:08:57+0100    error: /default/check_generic_file_content/files/'/etc/hosts'[0]: Can't rename '/etc/hosts.cf-after-edit' to '/etc/hosts' - so promised edits could not be moved into place. (rename: Device or resource busy)
2016-03-18T00:08:57+0100    error: /default/check_generic_file_content/files/'/etc/hosts'[0]: Unable to save file '/etc/hosts' after editing

Not sure how this could be solved. I on my side did this by copying the file away, editing it, then cat'ing it back to the same inode it used to have.