Presumably, if the external disk mounts in MX but not in ubuntu, then the disk itself is not a hardware problem. In that case, it's the difference in mounting processes between the two distros that appear to be issue.
To investigate then, it would be useful to compare the mounting processes of both systems by looking into the log files to detect the differences and perhaps find an error report in the ubuntu logs.
Below are some example commands that could be helpful. Not all may apply, for example, if no syslog package is installed, there won't be a /var/log/syslog file.
Also, adjust the commands to fit your system by using the correct mount point and device name in the commands. Bear in mind that there may be a lot of output, but what is of interest is the mounting of the particular disk, so looking for logs with its device name and mount point would be useful.
Code:
journalctl -b
journalctl -b -x -p 3 --no-pager
dmesg
less /var/log/kern.log
less /var/log/syslog
less /var/log/messages
To see what options MX uses to mount the drive, run:
and perhaps use some of those options in a command to try and mount in ubuntu, in particular a rw option.
Check the permissions of the mount points in both distros e.g.:
It may be that the apparmor settings in ubuntu are interfering with the mounting of an external drive. One can alter apparmor enforcement by setting it to "complain mode" globally so it doesn't enforce compliance for the current boot. To do that run, as root or sudo:
Code:
echo -n complain > /sys/module/apparmor/parameters/mode
See the manpage for apparmor for details. Then try and mount the external disk and see what happens.