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small tweaks on container post

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AtelierSnek 2022-10-24 22:44:09 -07:00
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content/posts/rootless-containers-alpine.md
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@ -62,10 +62,11 @@ XDG_RUNTIME_DIR=/tmp/1000-runtime-dir
With that done, we can move onto our next steps.
### Sysctl
There's some sysctl config required for older distros, but it's not required on Alpine, so on we go.
There's some sysctl config required for older distros, but this isn't required for Alpine.
### User Namespace Configuration
Rootless Containers use User Namespaces, subUIDs, and subGIDs, so we'll need to have those working. The apk package `shadow-subids` provides that functionality for us.
Rootless Containers use User Namespaces, subUIDs, and subGIDs, so we'll need to have those working.
The apk package `shadow-subids` provides that functionality for us.
```
~ ❯ apk info shadow-subids
shadow-subids-4.10-r3 description:
@ -110,23 +111,39 @@ To enable CGroups in general, we need to set `rc_controller_cgroups` to `YES`
# /sys/fs/cgroup in hybrid or legacy mode.
rc_controller_cgroups="YES"
```
From here, we can enable CGroups V2 by setting `rc_cgroup_mode` to `hybrid`
From here, we can enable CGroups V2 by setting `rc_cgroup_mode` to `unified`
```sh
# This sets the mode used to mount cgroups.
# "hybrid" mounts cgroups version 2 on /sys/fs/cgroup/unified and
# cgroups version 1 on /sys/fs/cgroup.
# "legacy" mounts cgroups version 1 on /sys/fs/cgroup
# "unified" mounts cgroups version 2 on /sys/fs/cgroup
rc_cgroup_mode="hybrid"
rc_cgroup_mode="unified"
```
And configure the particular controllers we want to use:
**(Doll)**: Doll confused.
**(Ashe)** So was I, for a bit. Despite what `rc.conf` says, cgroups V2 does *not* seem to be enabled on Alpine
unless `rc_cgroup_mode` is set to `unified`. The [https://wiki.alpinelinux.org/wiki/OpenRC#cgroups\_v2](Alpine Wiki)
seems to agree here, but isn't super clear. We'll find out if this is sufficient.
Next step is configuring the controllers we want to use:
```sh
# This is a list of controllers which should be enabled for cgroups version 2
# when hybrid mode is being used.
# Controllers listed here will not be available for cgroups version 1.
rc_cgroup_controllers="cpuset cpu io memory hugetlb pids"
```
Now we just reboot and we're ready to go!
Finally, we can add cgroups to a runlevel so that it's started automatically at boot:
```sh
rc-update add cgroups
```
From here, we can reboot, and continue on. If you don't want to reboot, you can start the cgroup service manually:
```sh
rc-service cgroups start
```
## Configuring the Rootless containerd service
We'll be using nerdctl as our containerd controller of choice. It comes with a rootless containerd.service, but since Alpine doesn't use systemd, we'll have to adapt this into an rc service.