dpkg-deb: error:

HI
Get following errors when trying to upgrade my OMV 4.1.27-1

dpkg: error processing archive /var/cache/apt/archives/linux-headers-4.19.0-0.bpo.6-common-rt_4.19.67-2+deb10u2~bpo9+1_all.deb (--unpack):
unable to create '/usr/src/linux-headers-4.19.0-0.bpo.6-common-rt/include/linux/of_graph.h.dpkg-new' (while processing './usr/src/linux-headers-4.19.0-0.bpo.6-common-rt/include/linux/of_graph.h'): No space left on device
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Preparing to unpack .../linux-headers-4.19.0-0.bpo.6-rt-amd64_4.19.67-2+deb10u2~bpo9+1_amd64.deb ...
Unpacking linux-headers-4.19.0-0.bpo.6-rt-amd64 (4.19.67-2+deb10u2~bpo9+1) ...
dpkg: error processing archive /var/cache/apt/archives/linux-headers-4.19.0-0.bpo.6-rt-amd64_4.19.67-2+deb10u2~bpo9+1_amd64.deb (--unpack):
unable to create '/usr/src/linux-headers-4.19.0-0.bpo.6-rt-amd64/include/config/infiniband/hfi1.h.dpkg-new' (while processing './usr/src/linux-headers-4.19.0-0.bpo.6-rt-amd64/include/config/infiniband/hfi1.h'): No space left on device
dpkg-deb: error: subprocess paste was killed by signal (Broken pipe)
Errors were encountered while processing:
/var/cache/apt/archives/linux-headers-4.19.0-0.bpo.6-common-rt_4.19.67-2+deb10u2~bpo9+1_all.deb
/var/cache/apt/archives/linux-headers-4.19.0-0.bpo.6-rt-amd64_4.19.67-2+deb10u2~bpo9+1_amd64.deb
E: Sub-process /usr/bin/dpkg returned an error code (1)
root@openmediavault:~#

Any help here ??

Thanks for reply
Here is the output:
root@openmediavault:~# du -d1 -h -x /
12M /etc
12K /media
344K /root
160K /opt
16K /lost+found
4.0K /lib64
4.0K /sharedfolders
13M /bin
613M /var
4.0K /mnt
446M /boot
16K /srv
4.0K /export
4.0K /home
2.8G /usr
3.1G /lib
15M /sbin
6.9G /

What to do next ??