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root@openmediavault:/srv# grep fuse /etc/fstab
/srv/dev-disk-by-id-ata-WDC_WD15EADS-00P8B0_WD-WMAVU0832198-part1:/srv/dev-disk-by-id-ata-MAXTOR_STM3250310AS_6RY3A9KZ-part1 /srv/c4c6c5b1-76df-4fe0-b6e9-dee25caea041 fuse.mergerfs defaults,allow_other,direct_io,use_ino,category.create=epmfs,minfreespace=4G 0 0
root@openmediavault:/srv# ls -alth /srv
ls: cannot access '/srv/c4c6c5b1-76df-4fe0-b6e9-dee25caea041': No such file or directory
ls: cannot access '/srv/897fdf50-46e0-4ec1-8542-470409a78b1e': No such file or directory
total 56K
drwxr-xr-x 10 root root 4.0K Oct 26 06:27 .
drwxr-xr-x 4 root root 4.0K Oct 26 06:24 dev-disk-by-id-ata-MAXTOR_STM3250310AS_6RY3A9KZ-part1
drwxr-xr-x 1 root root 74 Oct 24 16:00 dev-disk-by-id-ata-WDC_WD15EADS-00P8B0_WD-WMAVU0832198-part1
drwxr-xr-x 1 root root 30 Oct 24 16:00 dev-disk-by-id-ata-WDC_WD15EADS-00P8B0_WD-WMAVU0114055-part1
drwxrwxr-x 20 root root 4.0K Oct 21 17:39 ..
drwxr-xr-x 5 root root 4.0K Oct 21 17:26 salt
drwxr-xr-x 3 root root 4.0K Oct 21 17:26 pillar
drwxr-xr-x 2 ftp nogroup 4.0K Oct 21 17:26 ftp
d????????? ? ? ? ? ? 897fdf50-46e0-4ec1-8542-470409a78b1e
d????????? ? ? ? ? ? c4c6c5b1-76df-4fe0-b6e9-dee25caea041
So I've just started using openmediavault - from the website it wasn't very obvious that OMV5 is BETA so I just picked the newest release. I'm getting a similar issue with the mergefs filesystem and looking in fstab and /srv I can see the above.
Looks like the mount point hasn't been created correctly? I then unmounted it and then ran mount -a and it now looks like this and it works.
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root@openmediavault:/srv# ls -alth
total 80K
drwxr-xr-x 1 root root 86 Oct 26 06:47 c4c6c5b1-76df-4fe0-b6e9-dee25caea041
drwxr-xr-x 1 root root 86 Oct 26 06:47 dev-disk-by-id-ata-WDC_WD15EADS-00P8B0_WD-WMAVU0832198-part1
drwxr-xr-x 11 root root 4.0K Oct 26 06:43 .
drwxr-xr-x 2 root root 4.0K Oct 26 06:43 pool
drwxr-xr-x 4 root root 4.0K Oct 26 06:24 dev-disk-by-id-ata-MAXTOR_STM3250310AS_6RY3A9KZ-part1
drwxrwxrwx 2 root root 4.0K Oct 25 07:08 897fdf50-46e0-4ec1-8542-470409a78b1e
drwxr-xr-x 1 root root 30 Oct 24 16:00 dev-disk-by-id-ata-WDC_WD15EADS-00P8B0_WD-WMAVU0114055-part1
drwxrwxr-x 20 root root 4.0K Oct 21 17:39 ..
drwxr-xr-x 5 root root 4.0K Oct 21 17:26 salt
drwxr-xr-x 3 root root 4.0K Oct 21 17:26 pillar
drwxr-xr-x 2 ftp nogroup 4.0K Oct 21 17:26 ftp
Hope that helps in some way although I suspect you already know what i've found.