| Summary: | systemd breaks /dev/console if run in a container | ||||||
|---|---|---|---|---|---|---|---|
| Product: | [Fedora] Fedora | Reporter: | Dietmar Kling <baldur> | ||||
| Component: | systemd | Assignee: | systemd-maint | ||||
| Status: | CLOSED NOTABUG | QA Contact: | Fedora Extras Quality Assurance <extras-qa> | ||||
| Severity: | high | Docs Contact: | |||||
| Priority: | unspecified | ||||||
| Version: | 25 | CC: | johannbg, lnykryn, msekleta, muadda, ssahani, s, systemd-maint, zbyszek | ||||
| Target Milestone: | --- | ||||||
| Target Release: | --- | ||||||
| Hardware: | x86_64 | ||||||
| OS: | Linux | ||||||
| Whiteboard: | |||||||
| Fixed In Version: | Doc Type: | If docs needed, set a value | |||||
| Doc Text: | Story Points: | --- | |||||
| Clone Of: | Environment: | ||||||
| Last Closed: | 2016-11-04 00:04:37 UTC | Type: | Bug | ||||
| Regression: | --- | Mount Type: | --- | ||||
| Documentation: | --- | CRM: | |||||
| Verified Versions: | Category: | --- | |||||
| oVirt Team: | --- | RHEL 7.3 requirements from Atomic Host: | |||||
| Cloudforms Team: | --- | Target Upstream Version: | |||||
| Attachments: |
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This was discussed upstream, with the conclusion that this is not a systemd bug: https://github.com/systemd/systemd/pull/4262. Please see the the upstream discussion for details. |
Created attachment 1206501 [details] Bugfix for systemd running in containers Description of problem: I run some service in a container with systemd. I noticed an incredible slowdown on docker containers in Fedora 25. When I debbuged the problem, it turned out that journald, which was configured to log to /dev/console, desperatly tried to open /dev/console for each log message an failed, because /dev/console was reported as "//deleted" if you did a cat /proc/1/mountinfo. e.g. cat /proc/1/mountinfo |grep console 2769 2749 0:20 /33//deleted /dev/console rw,nosuid,noexec,relatime - devpts devpts rw,gid=5,mode=620,ptmxmode=000 The root cause for this behaviour is systemd - which when run not as process 1 in the container, did _not_ close the /dev/console. Version-Release number of selected component (if applicable): systemd-231-6 How reproducible: Steps to Reproduce: 1. run systemd in docker container 2. docker exec -it <containername> bash 3. echo TEST >/dev/console Actual results: The echo returns an error and after some research i found that /dev/console is closed by systemd on startup. Expected results: Working /dev/console Additional info: I have traced the problem down in systemd/src/core/main.c which calls in the main function make_null_stdio(). If you comment out this function, systemd starts working again in the docker container and /dev/console just works as expected. I have analyzed the problem further, the following seems to happen: IN src/basic/terminal-util.c where make_null_stdio() resides, the functions opens "/dev/null" and passes the filedescriptor to make_stdio(fd) in the same file. make_stdio(int fd) contains s = dup2(fd, STDOUT_FILENO); This actually closes STDOUT_FILEN which is connected to the filehandle where the docker host receives the console messages. After this point /dev/console in the docker container is broken and cannot be used anymore. Therefore e.g. a docker logs -f <container> does not get any message from journald (which is configured to log to console) The attached patch disables make_null_stdio() for systemd when run in a container, which makes it useable again in docker.