Ubuntu – cifs mount fails with “mount error(112): Host is down”

On the server (sharing) side : right click on folder you want to share (e.g Documents) then click properties :

Enable sharing option (nautilus will download and install samba for you). You may also need to check access for guests.

On the client side :

sudo apt-get install cifs-utils

and mount it (as guest) :

sudo mount -t cifs -o guest //sharing_machine_ip/Documents /mountpoint

you can also add some other options like user and password:

sudo mount -t cifs -o username=your_username,password=your_password //sharing_machine_ip/Documents /mountpoint

If you want this to automount (as guest - indicates you don't need a password to access the share) at startup you can add to the end of /etc/fstab:

//sharing_machine_ip/Documents  /your_mountpoint  cifs  guest   0 0

or with password protected share:

//sharing_machine_ip/Documents  /your_mountpoint  cifs  username=your_username,password=your_password   0 0

I recommend you use fstab for mounting.

Try to check the logs to troubleshoot the causes of your problem, try this command to display the list of files which could display the mount logs:

grep -e mount -e ext4 -lR /var/log 2> /dev/null

For me, the mount logs were in /var/log/syslog it may be different for you.

Now you need two terminal tabs open, enter the command on one tab: sudo tail -f /var/log/syslog

And on the second tab, try to mount the system with the following command:

mount -t cifs -o user=USER,domain=DOMAIN,cruid=USER,sec=krb5 //HOST/Share /mnt/tmp

If you go back to your first tab you should be able to see some log errors. For me the errors were(for you it may be different):

   kernel: No dialect specified on mount. Default has changed to a more secure dialect, SMB2.1 or later (e.g. SMB3), from CIFS (SMB1). To use the less secure SMB1 dialect to access old servers which do not support SMB3 (or SMB2.1) specify vers=1.0 on mount.
   kernel: CIFS VFS: protocol revalidation - security settings mismatch
   kernel: CIFS VFS: session ffff90a6a2959000 has no tcon available for a dfs referral request
   kernel: CIFS VFS: cifs_mount failed w/return code = -5

Depending on your error logs, you may be able to get away with adding vers=1.0 to your mount command and this could work but it is the less secure version of smb. Otherwise, you could workout what the solution is based on the error you get.

What you could also try is configure the Samba server inside /etc/samba/smb.conf similar to this (it works for me):

[username]
   comment = Username's developer directory
   read only = no
   locking = no
   path = /var/www/username
   guest ok = no
   writeable = yes

Then on the client, add the following line to /etc/fstab

//server/username /mountpoint cifs vers=1.0,username=username,iocharset=utf8,uid=your_profile_uid_on_the_server 0 0

Use sudo mount /mountpint See how this goes, hopefully this information will be useful to you.