buildah-unshare - Man Page

buildah unshare [options] [--] [command]

Launches a process (by default, $SHELL) in a new user namespace.  The user namespace is configured so that the invoking user's UID and primary GID appear to be UID 0 and GID 0, respectively.  Any ranges which match that user and group in /etc/subuid and /etc/subgid are also mapped in as themselves with the help of the newuidmap(1) and newgidmap(1) helpers.

buildah unshare is useful for troubleshooting unprivileged operations and for manually clearing storage and other data related to images and containers.

It is also useful if you want to use the buildah mount command.  If an unprivileged user wants to mount and work with a container, then they need to execute buildah unshare.  Executing buildah mount fails for unprivileged users unless the user is running inside a buildah unshare session.

--mount,  -m [VARIABLE=]containerNameOrID

Mount the containerNameOrID container while running command, and set the environment variable VARIABLE to the path of the mountpoint.  If VARIABLE is not specified, it defaults to containerNameOrID, which may not be a valid name for an environment variable.

buildah unshare id

buildah unshare pwd

buildah unshare cat /proc/self/uid_map /proc/self/gid_map

buildah unshare rm -fr $HOME/.local/share/containers/storage /run/user/`id -u`/run

buildah unshare --mount containerID sh -c 'cat ${containerID}/etc/os-release'

If you want to use buildah with a mount command then you can create a script that looks something like:

cat buildah-script.sh << _EOF
#!/bin/sh
ctr=$(buildah from scratch)
mnt=$(buildah mount $ctr)
dnf -y install --installroot=$mnt PACKAGES
dnf -y clean all --installroot=$mnt
buildah config --entrypoint="/bin/PACKAGE" --env "FOO=BAR" $ctr
buildah commit $ctr imagename
buildah unmount $ctr
_EOF

Then execute it with:

buildah unshare buildah-script.sh

buildah(1), buildah-mount(1), namespaces(7), newuidmap(1), newgidmap(1), user_namespaces(7)

buildah(1), buildah-mount(1).