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Document how to enable CPU limit delegation

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Signed-off-by: Jordan Christiansen <xordspar0@gmail.com>
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Jordan Christiansen
2020-10-24 22:35:29 -05:00
parent 6fa6470d24
commit f393d32e96
4 changed files with 70 additions and 2 deletions
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12
docs/source/markdown/podman-build.1.md
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@ -115,6 +115,10 @@ Limit the CPU CFS (Completely Fair Scheduler) period
Limit the container's CPU usage. This flag tell the kernel to restrict the container's CPU usage to the period you specify.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpu-quota**=*limit*
Limit the CPU CFS (Completely Fair Scheduler) quota
@ -123,6 +127,10 @@ Limit the container's CPU usage. By default, containers run with the full
CPU resource. This flag tell the kernel to restrict the container's CPU usage
to the quota you specify.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpu-shares**, **-c**=*shares*
CPU shares (relative weight)
@ -787,9 +795,9 @@ registries.conf is the configuration file which specifies which container regist
## Troubleshooting
If you are using a useradd command within a Containerfile with a large UID/GID, it will create a large sparse file `/var/log/lastlog`. This can cause the build to hang forever. Go language does not support sparse files correctly, which can lead to some huge files being created in your container image.
### lastlog sparse file
### Solution
If you are using a useradd command within a Containerfile with a large UID/GID, it will create a large sparse file `/var/log/lastlog`. This can cause the build to hang forever. Go language does not support sparse files correctly, which can lead to some huge files being created in your container image.
If you are using `useradd` within your build script, you should pass the `--no-log-init or -l` option to the `useradd` command. This option tells useradd to stop creating the lastlog file.

12
docs/source/markdown/podman-create.1.md
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@ -107,6 +107,10 @@ Limit the CPU CFS (Completely Fair Scheduler) period
Limit the container's CPU usage. This flag tell the kernel to restrict the container's CPU usage to the period you specify.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpu-quota**=*limit*
Limit the CPU CFS (Completely Fair Scheduler) quota
@ -115,6 +119,10 @@ Limit the container's CPU usage. By default, containers run with the full
CPU resource. This flag tell the kernel to restrict the container's CPU usage
to the quota you specify.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpu-rt-period**=*microseconds*
Limit the CPU real-time period in microseconds
@ -171,6 +179,10 @@ PID container CPU CPU share
Number of CPUs. The default is *0.0* which means no limit.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpuset-cpus**=*cpus*
CPUs in which to allow execution (0-3, 0,1)

12
docs/source/markdown/podman-run.1.md
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@ -120,6 +120,10 @@ Write the pid of the **conmon** process to a file. As **conmon** runs in a separ
Limit the container's CPU usage by setting CPU CFS (Completely Fair Scheduler) period.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpu-quota**=*limit*
Limit the CPU CFS (Completely Fair Scheduler) quota.
@ -128,6 +132,10 @@ Limit the container's CPU usage. By default, containers run with the full
CPU resource. This flag tell the kernel to restrict the container's CPU usage
to the quota you specify.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpu-rt-period**=*microseconds*
Limit the CPU real-time period in microseconds.
@ -182,6 +190,10 @@ division of CPU shares:
Number of CPUs. The default is *0.0* which means no limit.
On some systems, changing the CPU limits may not be allowed for non-root
users. For more details, see
https://github.com/containers/podman/blob/master/troubleshooting.md#26-running-containers-with-cpu-limits-fails-with-a-permissions-error
**--cpuset-cpus**=*number*
CPUs in which to allow execution. Can be specified as a comma-separated list

36
troubleshooting.md
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@ -644,3 +644,39 @@ $ podman run --read-only --rootfs /path/to/rootfs ....
Another option would be to create an overlay file system on the directory as a lower and then
then allow podman to create the files on the upper.
### 26) Running containers with CPU limits fails with a permissions error
On some systemd-based systems, non-root users do not have CPU limit delegation
permissions. This causes setting CPU limits to fail.
#### Symptom
Running a container with a CPU limit options such as `--cpus`, `--cpu-period`,
or `--cpu-quota` will fail with an error similar to the following:
Error: opening file `cpu.max` for writing: Permission denied: OCI runtime permission denied error
This means that CPU limit delegation is not enabled for the current user.
#### Solution
You can verify whether CPU limit delegation is enabled by running the following command:
cat "/sys/fs/cgroup/user.slice/user-$(id -u).slice/user@$(id -u).service/cgroup.controllers"
Example output might be:
memory pids
In the above example, `cpu` is not listed, which means the curent user does
not have permission to set CPU limits.
If you want to enable CPU limit delegation for all users, you can create the
file `/etc/systemd/system/user@.service.d/delegate.conf` with the contents:
[Service]
Delegate=memory pids cpu io
After logging out and loggin back in, you should have permission to set CPU
limits.