Red Hat Bugzilla – Bug 1291020
no processes producing IO are listed when run in (privileged) docker container
Last modified: 2016-12-20 11:58:01 EST
Description of problem:
When running iotop in a privileged docker container, it doesn't list any processes that are producing reads and/or writes to disk.
Version-Release number of selected component (if applicable):
Steps to Reproduce:
1. System is based on Fedora-Cloud_Atomic-x86_64-23.iso, with tree 23.29 deployed.
2. On host, btrfs check <dev>, and also btrfs scrub start. So there should be at least one btrfs process running with the attached strace, producing IO.
2. docker run --net=host -v /dev:/dev --privileged=true -it fedext /usr/sbin/iotop -d3
No processes listed, see screen shot which shows there is read IO happening, but no processes are listed.
When run outside of docker the process listing without -o is rather lengthy, but this has only two processes neither of which are btrfs user space tool doing the check or scrub.
I expect the same behavior in docker.
Started out here when it was crashing in docker, bug --net=host
Created attachment 1105172 [details]
strace iotop -d3
The result of 'strace iotop -d' inside a docker container run with command 'docker run --net=host -v /dev:/dev --privileged=true -it fedext /bin/bash' while the host was running 'btrfs check /dev/sda' and producing a bunch of read IO.
Created attachment 1105173 [details]
This is a screenshot of what I see with 'iotop -d3' when run in the privileged docker container.
Notice a textUI anomaly that's weird: the 3rd row (black text on white), between the SWAPIN and COMMAND columns is this phantom IO> text. This phantom text doesn't appear when the command is run outside of a container.
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