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VirtualBox 5.1.20 bug with Shared Folders (RHEL 7 guest)

Upgraded VirtualBox (as is my wont to do) and found the following problem after reinstalling the newer Guest Additions.
I've submitted a bug report 16697 for this.

# mount host_home
mount: wrong fs type, bad option, bad superblock on host_home,
       missing codepage or helper program, or other error

       In some cases useful info is found in syslog - try
       dmesg | tail or so.
dmesg tells me the following (I had already tried rebuilding the GA with rcvboxadd setup -- the systemd equivalent of /etc/init.d/vboxadd setup)
# dmesg | tail
[  334.616717] vboxsf: Successfully loaded version 5.1.20 (interface 0x00010004)
[  343.413650] sf_read_super_aux err=-22
A similar report from an earlier version suggested a installation bug with library locations, so looking around ...
# updatedb

# locate mount.vbox

# ls -l /usr/sbin/mount.vboxsf 
lrwxrwxrwx. 1 root root 49 Apr 26 10:04 /usr/sbin/mount.vboxsf 
    -> /opt/VBoxGuestAdditions-5.1.20/other/mount.vboxsf
Aha, it seems that mount.vboxsf is a broken link; the following are not the same:
/opt/VBoxGuestAdditions-5.1.20/lib/VBoxGuestAdditions/mount.vboxsf  <--- at="" available="" mount.vboxsf="" opt="" other="" oxguestadditions-5.1.20="" pointed="" pre="">

Bit of a quicky fix:
# rm -f /usr/sbin/mount.vboxsf

# ln -s /opt/VBoxGuestAdditions-5.1.20/lib/VBoxGuestAdditions/mount.vboxsf \

# ls -l /usr/sbin/mount.vboxsf 
lrwxrwxrwx. 1 root root 66 Apr 26 10:16 /usr/sbin/mount.vboxsf 
    -> /opt/VBoxGuestAdditions-5.1.20/lib/VBoxGuestAdditions/mount.vboxsf
Moment of truth:
# mount host_home

$ mount
host_home on /home/ckerr/host_home type vboxsf (rw,nodev,relatime)
Hallelujah! Though it does seem like something that should have been picked up in testing. I dare say the next version will have this fixed.


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