For over a year, I've been able to backup numerous Windows servers using Ubuntu Server 16.04, but this all stopped working on Tuesday May 9th 2017.
Here's how I'm mounting these windows file systems using fstab:
sudo nano /etc/fstab \\192.168.1.1\c$ /mnt/win2012r2 cifs credentials=/home/user/.smb,iocharset=utf8,sec=ntlm 0 0 \\192.168.1.2\d$ /mnt/win2008r2 cifs credentials=/home/user/.smb,iocharset=utf8,sec=ntlm 0 0 \\192.168.1.3\c$ /mnt/win2012 cifs credentials=/home/user/.smb,iocharset=utf8,sec=ntlm 0 0 \\192.168.1.4\d$ /mnt/win2008 cifs credentials=/home/user/.smb,iocharset=utf8,sec=ntlm 0 0
The /home/user/.smb file contains only this:
username=administrator2 password=s3cr3tPW domain=company1
After a reboot, if I attempt to do a mount command, it shows that all of theses server's drives are already mounted to the linux file system:
sudo mount -a --verbose -vvv /mnt/win2012r2 : already mounted /mnt/win2008r2 : already mounted /mnt/win2012 : already mounted /mnt/win2008 : already mounted
However, if I try to list the directory where these mount-points are, it takes forever and eventually says these hosts are down:
ls /mnt ls: cannot access 'win2012r2': Host is down ls: cannot access 'win2008r2': Host is down ls: cannot access 'win2012': Host is down ls: cannot access 'win2008': Host is down
Above, is essentially the same error that I also see in my cron rsync logs:
failed: Host is down (112)
Again, this all started on Tuesday May 9th 2017. And, it is not just happening on this one network; its the same story at a completely different company where I'm using the same method for backup.
Lastly, no settings have been changed recently on these backup servers. I don't even recall explicitly doing any updates between May 8th and 9th.