github.com/containers/podman/v2@v2.2.2-0.20210501105131-c1e07d070c4c/rootless.md (about)

     1  # Shortcomings of Rootless Podman
     2  
     3  The following list categorizes the known issues and irregularities with running Podman as a non-root user.  Although currently functional, there is still a number of work items that are under consideration to be added.  These proposed changes are in varying degrees of design and development.
     4  
     5  Contributors are more than welcomed to help with this work.  If you decide to carve off a piece and work on it, please create an issue in [GitHub](https://github.com/containers/podman/issues), and assign it to yourself.  If you find other unexpected behavior with rootless Podman and feel it’s warranted, please feel free to update this document.
     6  
     7  * Podman can not create containers that bind to ports < 1024.
     8    * The kernel does not allow processes without CAP_NET_BIND_SERVICE to bind to low ports.
     9    * You can modify the `net.ipv4.ip_unprivileged_port_start` sysctl to change the lowest port.  For example `sysctl net.ipv4.ip_unprivileged_port_start=443` allows rootless Podman containers to bind to ports >= 443.
    10  * “How To” documentation is patchy at best.
    11  * If /etc/subuid and /etc/subgid are not setup for a user, then podman commands
    12  can easily fail
    13    * This can be a big issue on machines using Network Based Password information (FreeIPA, Active Directory, LDAP)
    14    * We are working to get support for NSSWITCH on the /etc/subuid and /etc/subgid files.
    15  * No cgroup V1 Support
    16    * cgroup V1 does not safely support cgroup delegation.
    17    * As of Fedora 31 defaults to cgroup V2, which has full support of rootless cgroup management.  Note this requires the --cgroup-manager within rootless containers to use systemd, which new containers will get by default.
    18  * Some system unit configuration options do not work in the rootless container
    19    * systemd fails to apply several options and failures are silently ignored (e.g. CPUShares, MemoryLimit). Should work on cgroup V2.
    20    * Use of certain options will cause service startup failures (e.g. PrivateNetwork).  The systemd services requiring `PrivateNetwork` can be made to work by passing `--cap-add SYS_ADMIN`, but the security implications should be carefully evaluated.  In most cases, it's better to create an override.conf drop-in that sets `PrivateNetwork=no`.  This also applies to containers run by root.
    21  * Can not share container images with CRI-O or other rootfull users
    22  * Difficult to use additional stores for sharing content
    23  * Does not work on NFS or parallel filesystem homedirs (e.g. [GPFS](https://www.ibm.com/support/knowledgecenter/en/SSFKCN/gpfs_welcome.html))
    24    * NFS and parallel filesystems enforce file creation on different UIDs on the server side and does not understand User Namespace.
    25    * When a container root process like YUM attempts to create a file owned by a different UID, NFS Server/GPFS denies the creation.
    26  * Does not work with homedirs mounted with noexec/nodev
    27    * User can setup storage to point to other directories they can write to that are not mounted noexec/nodev
    28  * Can not use overlayfs driver, but does support fuse-overlayfs
    29    * Ubuntu supports non root overlay, but no other Linux distros do.
    30  * Only other supported driver is VFS.
    31  * Cannot use ping out of the box.
    32    * [(Can be fixed by setting sysctl on host)](https://github.com/containers/podman/blob/master/troubleshooting.md#6-rootless-containers-cannot-ping-hosts)
    33  * Requires new shadow-utils (not found in older (RHEL7/Centos7 distros) Should be fixed in RHEL7.7 release)
    34  * A few commands do not work.
    35    * mount/unmount (on fuse-overlay)
    36       * Only works if you enter the mount namespace with podman unshare
    37    * podman stats (Works with cgroup V2 support)
    38    * Checkpoint and Restore (CRIU requires root)
    39    * Pause and Unpause (Works with cgroup V2 support)
    40  * Issues with higher UIDs can cause builds to fail
    41    * If a build is attempting to use a UID that is not mapped into the user namespace mapping for a container, then builds will not be able to put the UID in an image.
    42  * Making device nodes within a container fails, even when running --privileged.
    43    * The kernel does not allow non root user processes (processes without CAP_MKNOD) to create device nodes.  If a container needs to create device nodes, it must be run as root.
    44  * When using --net=host with rootless containers, subsequent podman execs to that container will not join the host network namespace because it is owned by root.