NAME

       umoci unpack - Unpacks an OCI image tag into an runtime bundle

SYNOPSIS

       umoci unpack --image=image[:tag] [--rootless] [--uid-map=value] [--uid-map=value]
       [--keep-dirlinks] bundle

DESCRIPTION

       Extracts all of the layers (deterministically) to an OCI runtime bundle at the path
       bundle, as well as generating an OCI runtime configuration that corresponds to the image's
       configuration. In addition, an mtree(8) specification is generated at the time of
       unpacking to allow filesystem deltas to be generated by umoci-repack(1) and thus allowing
       for the creation of layered OCI images.

OPTIONS

       The global options are defined in umoci(1).

       --image=image[:tag]
         The OCI image tag which will be extracted to the bundle. image must be a
         path to a valid OCI image and tag must be a valid tag in the image. If
         tag is not provided it defaults to "latest".

       --rootless
         Enable rootless unpacking support. This allows for umoci-unpack(1) and
         umoci-repack(1) to be used as an unprivileged user. Use of this flag
         implies --uid-map=0:$(id -u):1 and --gid-map=0:$(id -g):1, as well as
         enabling several features to fake parts of the unpacking in an attempt to
         generate an as-close-as-possible extraction of the filesystem. Note that it
         is almost always not possible to perfectly extract an OCI image with
         --rootless, but it will be as close as possible.

       --uid-map=value
         Specifies a UID mapping to use while unpacking (and repacking) layers. This
         is used in a similar fashion to user_namespaces(7), and is of the form
         container:host[:size].

       --gid-map=value
         Specifies a GID mapping to use while unpacking (and repacking) layers. This
         is used in a similar fashion to user_namespaces(7), and is of the form
         container:host[:size].

       --keep-dirlinks
         Instead of overwriting directories which are links to other directories when
         higher layers have an explicit directory, just write through the symlink.
         This option is inspired by rsync's option of the same name.

EXAMPLE

       The following downloads an image from a docker(1) registry using skopeo(1), unpacks said
       image and then creates a new container using the extracted OCI runtime bundle with
       runc(8). Then, the image is repacked with umoci-repack(1).

              % skopeo copy docker://opensuse/amd64:42.2 oci:image:latest
              # umoci unpack --image image bundle
              # runc run -b bundle ctr
              [ container session ]
              # umoci repack --image image bundle

       With --rootless it is also possible to do the above example without root privileges. umoci
       will generate a configuration that works with rootless containers in runc(8).

              % skopeo copy docker://opensuse/amd64:42.2 oci:image:latest
              % umoci unpack --image image --rootless bundle
              % runc --root $HOME/runc run -b bundle ctr
              [ rootless container session ]
              % umoci repack --image image --rootless bundle

SEE ALSO

       umoci(1), umoci-repack(1), runc(8)