NeilBrown
83897d5470
"-c", which is short for "--no-canonicalize", tells /bin/umount that the path name is canonical (no .. or symlinks etc). systemd always uses a canonical name, so this flag is appropriate for systemd to use. Knowing that the path is canonical allows umount to avoid some calls to lstat() on the path. From v2.30 "-c" goes further and causes umount to avoid all attempts to 'lstat()' (or similar) the path. This is important when automatically unmounting a filesystem, as lstat() can hang indefinitely in some cases such as when an NFS server is not accessible. "-c" has been supported since util-linux 2.17 which is before the earliest version supported by systemd. So "-c" is safe to use now, and once util-linux v2.30 is in use, it will allow mounts from non-responsive NFS servers to be unmounted.
systemd - System and Service Manager
Details
General information about systemd can be found in the systemd Wiki.
Information about build requirements are provided in the README file.
Consult our NEWS file for information about what's new in the most recent systemd versions.
Please see the HACKING file for information how to hack on systemd and test your modifications.
Please see our Contribution Guidelines for more information about filing GitHub Issues and posting GitHub Pull Requests.
When preparing patches for systemd, please follow our Coding Style Guidelines.
If you are looking for support, please contact our mailing list or join our IRC channel.