An der Stelle schon mal vielen Dank für die Hilfe...
Ach ja, falls noch wichtig:
Die zu sichernde, externe Festplatte ist formatiert in NTFS damit ich diese auch bei Win-Systemen anschließen kann (Büro Notebook...etc.)
Die externe Festplatte, auf die das Backup läuft, ist wiederum in ext4 formatiert (läuft auschließlich unter Ubuntu)
Das Problem besteht seit ungefähr Oktober letzten Jahres. Die letzte funktionierende Sicherung war Ende September. Danach wurde die Festplatte kurz abgezogen und wieder angeschlossen. Seitdem passierte erstmal nix (Urlaub, Umzug...etc.) aber so langsam wird die Thematik dringend 😉
mount:
marc@marc-OptiPlex-760:~$ mount
sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,nosuid,relatime,size=1914032k,nr_inodes=478508,mode=755)
devpts on /dev/pts type devpts (rw,nosuid,noexec,relatime,gid=5,mode=620,ptmxmode=000)
tmpfs on /run type tmpfs (rw,nosuid,noexec,relatime,size=387288k,mode=755)
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro,data=ordered)
securityfs on /sys/kernel/security type securityfs (rw,nosuid,nodev,noexec,relatime)
tmpfs on /dev/shm type tmpfs (rw,nosuid,nodev)
tmpfs on /run/lock type tmpfs (rw,nosuid,nodev,noexec,relatime,size=5120k)
tmpfs on /sys/fs/cgroup type tmpfs (ro,nosuid,nodev,noexec,mode=755)
cgroup on /sys/fs/cgroup/unified type cgroup2 (rw,nosuid,nodev,noexec,relatime,nsdelegate)
cgroup on /sys/fs/cgroup/systemd type cgroup (rw,nosuid,nodev,noexec,relatime,xattr,name=systemd)
pstore on /sys/fs/pstore type pstore (rw,nosuid,nodev,noexec,relatime)
cgroup on /sys/fs/cgroup/net_cls,net_prio type cgroup (rw,nosuid,nodev,noexec,relatime,net_cls,net_prio)
cgroup on /sys/fs/cgroup/cpu,cpuacct type cgroup (rw,nosuid,nodev,noexec,relatime,cpu,cpuacct)
cgroup on /sys/fs/cgroup/hugetlb type cgroup (rw,nosuid,nodev,noexec,relatime,hugetlb)
cgroup on /sys/fs/cgroup/devices type cgroup (rw,nosuid,nodev,noexec,relatime,devices)
cgroup on /sys/fs/cgroup/memory type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
cgroup on /sys/fs/cgroup/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset)
cgroup on /sys/fs/cgroup/freezer type cgroup (rw,nosuid,nodev,noexec,relatime,freezer)
cgroup on /sys/fs/cgroup/perf_event type cgroup (rw,nosuid,nodev,noexec,relatime,perf_event)
cgroup on /sys/fs/cgroup/pids type cgroup (rw,nosuid,nodev,noexec,relatime,pids)
cgroup on /sys/fs/cgroup/rdma type cgroup (rw,nosuid,nodev,noexec,relatime,rdma)
cgroup on /sys/fs/cgroup/blkio type cgroup (rw,nosuid,nodev,noexec,relatime,blkio)
systemd-1 on /proc/sys/fs/binfmt_misc type autofs (rw,relatime,fd=38,pgrp=1,timeout=0,minproto=5,maxproto=5,direct,pipe_ino=1880)
mqueue on /dev/mqueue type mqueue (rw,relatime)
hugetlbfs on /dev/hugepages type hugetlbfs (rw,relatime,pagesize=2M)
debugfs on /sys/kernel/debug type debugfs (rw,relatime)
fusectl on /sys/fs/fuse/connections type fusectl (rw,relatime)
configfs on /sys/kernel/config type configfs (rw,relatime)
/var/lib/snapd/snaps/core18_1705.snap on /snap/core18/1705 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gtk-common-themes_1506.snap on /snap/gtk-common-themes/1506 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gtk2-common-themes_5.snap on /snap/gtk2-common-themes/5 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gtk2-common-themes_9.snap on /snap/gtk2-common-themes/9 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/core_9066.snap on /snap/core/9066 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/vlc_1620.snap on /snap/vlc/1620 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/wine-platform-3-stable_6.snap on /snap/wine-platform-3-stable/6 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/core18_1754.snap on /snap/core18/1754 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gimp_252.snap on /snap/gimp/252 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/vlc_1397.snap on /snap/vlc/1397 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/wine-platform-5-stable_4.snap on /snap/wine-platform-5-stable/4 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/wine-platform-runtime_123.snap on /snap/wine-platform-runtime/123 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/foobar2000_294.snap on /snap/foobar2000/294 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/b1freearchiver_2.snap on /snap/b1freearchiver/2 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/foobar2000_293.snap on /snap/foobar2000/293 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gimp_273.snap on /snap/gimp/273 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gnome-3-28-1804_116.snap on /snap/gnome-3-28-1804/116 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gtk-common-themes_1502.snap on /snap/gtk-common-themes/1502 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/gnome-3-28-1804_110.snap on /snap/gnome-3-28-1804/110 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/core_8935.snap on /snap/core/8935 type squashfs (ro,nodev,relatime,x-gdu.hide)
/var/lib/snapd/snaps/b1freearchiver_1.snap on /snap/b1freearchiver/1 type squashfs (ro,nodev,relatime)
/var/lib/snapd/snaps/wine-platform-runtime_136.snap on /snap/wine-platform-runtime/136 type squashfs (ro,nodev,relatime,x-gdu.hide)
binfmt_misc on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,relatime)
tmpfs on /run/user/1000 type tmpfs (rw,nosuid,nodev,relatime,size=387284k,mode=700,uid=1000,gid=1000)
gvfsd-fuse on /run/user/1000/gvfs type fuse.gvfsd-fuse (rw,nosuid,nodev,relatime,user_id=1000,group_id=1000)
/dev/sdb1 on /mnt/usb-WD_My_Passport_0820_575832314141334B37343834-0:0-part1 type fuseblk (rw,nosuid,nodev,relatime,user_id=0,group_id=0,allow_other,blksize=4096,x-gvfs-show)
/dev/sdc1 on /media/marc/MV BACKUP type ext4 (rw,nosuid,nodev,relatime,data=ordered,uhelper=udisks2)
ls:
marc@marc-OptiPlex-760:~$ ls -aluh /media/$(whoami)
insgesamt 28K
drwxr-x---+ 7 root root 4,0K Mai 24 11:54 .
drwxr-xr-x 3 root root 4,0K Mai 22 21:10 ..
drwxr-xr-x 2 root root 4,0K Mär 28 20:59 Lenovo_Suite
drwxr-xr-x 2 root root 4,0K Mär 28 20:59 Lenovo_Suite1
drwxr-xr-x 2 root root 4,0K Mär 28 20:59 Lenovo_Suite2
drwx------ 3 marc marc 4,0K Mai 24 11:50 'MV BACKUP'
drwx------ 2 root root 4,0K Okt 25 2019 'MV DATEN'
cat:
marc@marc-OptiPlex-760:~$ cat /etc/fstab
# /etc/fstab: static file system information.
#
# Use 'blkid' to print the universally unique identifier for a
# device; this may be used with UUID= as a more robust way to name devices
# that works even if disks are added and removed. See fstab(5).
#
# <file system> <mount point> <type> <options> <dump> <pass>
# / was on /dev/sda1 during installation
UUID=c985c414-d838-43e9-b7a2-34f71a151a7a / ext4 errors=remount-ro 0 1
# swap was on /dev/sda5 during installation
UUID=7fb62355-5099-4171-b4a6-60134ecbeaf1 none swap sw 0 0
/dev/disk/by-id/usb-WD_My_Passport_0820_575832314141334B37343834-0:0-part1 /mnt/usb-WD_My_Passport_0820_575832314141334B37343834-0:0-part1 auto nosuid,nodev,nofail,x-gvfs-show,noauto 0 0