Thanks for trying to help 
ymir /home/jonesmz # urbackupclientctl list-backupdirs
PATH NAME FLAGS
/mnt mnt follow_symlinks,symlinks_optional,share_hashes
ymir /home/jonesmz # gawk ‘$1~//dev//{print $0}’ /proc/mounts
gawk: cmd. line:1: ‘~//dev//{print
gawk: cmd. line:1: ^ invalid char ‘���’ in expression
So I assume discourse did something screwy.
Rewriting it with the normal tick-marks I get
ymir /home/jonesmz # gawk ‘$1~//dev//{print $0}’
gawk: cmd. line:1: $1~//dev//{print $0}
gawk: cmd. line:1: ^ unterminated regexp
Presumably this is the information you’re looking for
ymir /home/jonesmz # grep -e “/dev/” /proc/mounts
/dev/sda3 / btrfs rw,noatime,compress=lzo,ssd,space_cache,subvolid=418,subvol=/@ 0 0
tmpfs /dev/shm tmpfs rw,nosuid,nodev 0 0
devpts /dev/pts devpts rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000 0 0
mqueue /dev/mqueue mqueue rw,relatime 0 0
hugetlbfs /dev/hugepages hugetlbfs rw,relatime,pagesize=2M 0 0
/dev/sda3 /mnt btrfs rw,noatime,compress=lzo,ssd,space_cache,subvolid=5,subvol=/ 0 0
/dev/sda3 /home btrfs rw,noatime,compress=lzo,ssd,space_cache,subvolid=1524,subvol=/@home 0 0
/dev/sda1 /boot vfat rw,relatime,fmask=0022,dmask=0022,codepage=437,iocharset=iso8859-1,shortname=mixed,errors=remount-ro 0 0
Note that /mnt/ has two folders
ymir /home/jonesmz # ls /mnt
@ @home
The @ folder is just another mount location for the btrfs subvolume of my root filesystem.
@home is another mount location for the btrfs subvolume for my home directory.
The main goal here is to backup everything on my local disk, but nothing that’s mounted from another filesystem. Since everything that would be mounted, e.g. network filesystems, kernel filesystems, so on, gets mounted under the “/” directory, and not the “/mnt” directory, I should be able to backup everything i want and nothing i don’t want by only backing up “/mnt” and subfolders.
Note further that I already have a nightly rsync process to back up “/mnt”, which works exactly as I expect, and I’m trying to replace that with Urbackup.
/usr/bin/rsync -arvh --inplace --delete-after /mnt/ rsync://backupprocess@mimir/nightly-operating-system-backup/%H/
However, the log clearly shows that urbackup is looking at folders outside of the indicated path
Feb 21 11:01:52 ymir systemd[1]: Started UrBackup backup client backend.
Feb 21 11:06:50 ymir urbackupclientbackend[238019]: 2019-02-21 11:06:50: ERROR: Error listing files in directory “/home/jonesmz/samba/Mikes_Files/.snapshots”: Permission denied (13)
Feb 21 11:06:50 ymir urbackupclientbackend[238019]: 2019-02-21 11:06:50: ERROR: Error while getting files in folder “/home/jonesmz/samba/Mikes_Files/.snapshots”. User may not have permissions to access this folder. Errno is 13
Feb 21 11:06:50 ymir urbackupclientbackend[238019]: 2019-02-21 11:06:50: ERROR: Indexing files failed, because of error
Where here /home/jonesmz/samba/Mikes_Files/ is a CIFS mount from a samba share on another machine.
The reason I want to backup /mnt/ and not / or /home is specifically to avoid Urbackup accessing /home/jonesmz/samba/*