Hi, This is not due to NFS, but due to the fact that the NFS mount is mounted nosuid (and nodev, probably). I can reproduce it on a local filesystem mounted nosuid.
It seems that, when remounting a bind mount which is originally nosuid inside a mount ns, you need to specify explicitely the nosuid option, or else can_change_locked_flags()[1] will return false. [1] https://github.com/torvalds/linux/blame/master/fs/namespace.c#L2480 There's a concept of "locked mount flags" that cannot be cleared by a less privileged user (see [2]). Our call to 'mount -o remount' ignores the fact that the filesystem is mounted nosuid (and does not include this flag), so the remount call tries to remove nosuid, and fails. [2] https://github.com/torvalds/linux/commit/9566d6742852c527bf5af38af5cbb878dad75705 This probably needs to be fixed in Guix by fetching the current mount flags and including them in the bind+remount+readonly call. Unfortunately I did not find an easy way to convert mount flags in /proc/$$/mountinfo to flags for the mount syscall... Lucas
