Project: Podman (App Definition and Development / Application Definition & Image Build)
File: userns.container.md

Set the user namespace mode for the container. If `--userns` is not set, the default value is determined as follows. If `--pod` is set, `--userns` is ignored and the user namespace of the pod is used. If the environment variable PODMAN_USERNS is set its value is used. If `userns` is specified in `containers.conf` this value is used. Otherwise, `--userns=host` is assumed. `--userns=""` (i.e., an empty string) is an alias for `--userns=host`. This option is incompatible with --gidmap, --uidmap, --subuidname and --subgidname. Rootless user --userns=Key mappings: Key | Host User | Container User |--| auto | $UID | nil (Host User UID is not mapped into container.) host | $UID | 0 (Default User account mapped to root user in container.) keep-id | $UID | $UID (Map user account to same UID within container.) keep-id:uid=200,gid=210 | $UID | 200:210 (Map user account to specified UID, GID value within container.) nomap | $UID | nil (Host User UID is not mapped into container.) Valid mode values are: auto[:OPTIONS,...]: automatically create a unique user namespace. `rootful mode`: The `--userns=auto` flag requires that the user name containers be specified in the /etc/subuid and /etc/subgid files, with an unused range of subordinate user IDs that Podman containers are allowed to allocate. Example: `containers:2147483647:2147483648`. `rootless mode`: The users range from the /etc/subuid and /etc/subgid files will be used. Note running a single container without using --userns=auto will use the entire range of UIDs and not allow further subdividing. See subuid(5). Podman allocates unique ranges of UIDs and GIDs from the `containers` subordinate user IDs. The size of the ranges is based on the number of UIDs required in the image. The number of UIDs and GIDs can be overridden with the `size` option. The option `--userns=keep-id` uses all the subuids and subgids of the user. The option `--userns=nomap` uses all the subuids and subgids of the user except the user's own ID. Using `--userns=auto` when starting new containers does not work as long as any containers exist that were started with `--userns=keep-id` or `--userns=nomap`. Valid `auto` options: gidmapping=CONTAINER\GID:HOST\GID:SIZE: to force a GID mapping to be present in the user namespace. size=SIZE: to specify an explicit size for the automatic user namespace. e.g. `--userns=auto:size=8192`. If `size` is not specified, `auto` estimates a size for the user namespace. uidmapping=CONTAINER\UID:HOST\UID:SIZE: to force a UID mapping to be present in the user namespace. The host UID and GID in gidmapping and uidmapping can optionally be prefixed with the `@` symbol. In this case, podman will look up the intermediate ID corresponding to host ID and it will map the found intermediate ID to the container id. For details see --uidmap. container:id: join the user namespace of the specified container. host or "" (empty string): run in the user namespace of the caller. The processes running in the container have the same privileges on the host as any other process launched by the calling user. keep-id: creates a user namespace where the current user's UID:GID are mapped to the same values in the container. For containers created by root, the current mapping is created into a new user namespace. Valid `keep-id` options: uid=UID: override the UID inside the container that is used to map the current user to. gid=GID: override the GID inside the container that is used to map the current user to. nomap: creates a user namespace where the current rootless user's UID:GID are not mapped into the container. This option is not allowed for containers created by the root user. ns:namespace: run the <<container|pod>> in the given existing user namespace.