Added k3s stuff

README.md

@@ -8,6 +8,7 @@
 * [Android](./android.md)
 * [containerization](./containerization)
     * [Docker](./containerization/docker.md)
+    * [k3s](./containerization/k3s.md)
     * [Podman](./containerization/podman/README.md)
 * [curl](./curl.md)
 * [git](./git/README.md)

containerization/k3s.md

@@ -0,0 +1,45 @@
+# K3s
+
+### Import image into containerd
+
+#### Offline
+
+On a host where one can pull the image:
+
+```
+podman save -o <image_file_name>.tar <image_name>:<image_version>
+gzip <image_file_name>.tar
+```
+
+Copy the file to target host(s) and then run:
+
+```
+zcat <image_file_name>.tar.gz | /usr/local/bin/k3s ctr images import -
+```
+
+#### Online
+
+```
+crictl pull <image_name_or_url>:<image_version>
+```
+
+If one needs to supply credentials for the registry, use:
+
+```
+   --auth AUTH_STRING                         Use AUTH_STRING for accessing the registry. AUTH_STRING is a base64
+                                              encoded 'USERNAME[:PASSWORD]' [$CRICTL_AUTH]
+   --creds USERNAME[:PASSWORD]                Use USERNAME[:PASSWORD] for accessing the registry [$CRICTL_CREDS]
+   --username USERNAME, -u USERNAME           Use USERNAME for accessing the registry. The password will be
+                                              requested on the command line
+```
+
+`-u` is most secure, as the password is not supplied on the command line.
+
+### Access shell of container with root rights (uid 0)
+
+Get container ID in the running pod:
+
+```
+kubectl -n hydra get pod <pod_name> -o jsonpath="{.status.containerStatuses[].containerID}" | sed 's,.*//,,'; echo ''
+k3s ctr task exec -t --exec-id <random_name> --user root <container_id> bash
+```