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Martin Roukala (né Peres) 8db2b4b733 man: Document the interaction between --systemd and --privileged
Users need to know about this side effect.

Fixes: 5a2405ae1b3a ("Don't mount /dev/tty* inside privileged...")
Fixes: f4c81b0aa5fd ("Only prevent VTs to be mounted inside ...")
Signed-off-by: Martin Roukala (né Peres) <martin.roukala@mupuf.org>
2023-01-16 16:23:53 +02:00

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####> This option file is used in:
####> podman create, run
####> If file is edited, make sure the changes
####> are applicable to all of those.
#### **--systemd**=*true* | *false* | *always*
Run container in systemd mode. The default is **true**.
- **true** enables systemd mode only when the command executed inside the container is *systemd*, */usr/sbin/init*,
*/sbin/init* or */usr/local/sbin/init*, systemd mode is enabled.
- **false** disables systemd mode.
- **always** enforces the systemd mode to be enabled.
Running the container in systemd mode causes the following changes:
* Podman mounts tmpfs file systems on the following directories
* _/run_
* _/run/lock_
* _/tmp_
* _/sys/fs/cgroup/systemd_
* _/var/lib/journal_
* Podman sets the default stop signal to **SIGRTMIN+3**.
* Podman sets **container_uuid** environment variable in the container to the
first 32 characters of the container id.
* Podman will not mount virtual consoles (_/dev/tty\d+_) when running with **--privileged**.
This allows systemd to run in a confined container without any modifications.
Note that on **SELinux** systems, systemd attempts to write to the cgroup
file system. Containers writing to the cgroup file system are denied by default.
The **container_manage_cgroup** boolean must be enabled for this to be allowed on an SELinux separated system.
```
setsebool -P container_manage_cgroup true
```