"Can't mount proc on /newroot/proc: Operation not permitted" if /proc/fs/nfsd is mounted

[jiri-janousek]

I cannot run flatpaks on Debian Jessie (Flatpak 0.6.14) when /proc/fs/nfsd is mounted:

$ mount | grep nfsd
nfsd on /proc/fs/nfsd type nfsd (rw,relatime)
$ flatpak run ...
Can't mount proc on /newroot/proc: Operation not permitted
$ sudo umount /proc/fs/nfsd
$ flatpak run ...
# Everything ok

[alexlarsson]

I believe this is a similar issue to containers/bubblewrap#134

[alexlarsson]

(But that one is for xen)

[alexlarsson]

Both are kernel-level bugs really. They need to create the proc mountpoint with proc_create_mount_point instead of proc_mkdir

[jgarciao]

I suddenly found that none of my installed flatpak apps weren't working and thanks to this issue I found the reason and the solution (Debian Jessie + nfs-kernel-server + flatpak don't get along!)

It might not be a problem in flatpak itself but maybe the error message could add a link to a troubleshooting section in docs.flatpak.org explaining the issue and solutions.