Thanks for all the replies to the Error Messages. I don't know how you find which disk is referred to by ata5.
I think dm-0 is a reference to a Raid setup. Other information about my hardware and rebooting :- I have two 1 TB hard drives arranged as a RAID 1 array. The power supply :- Corsair TXM Gold 550 W 80+ Gold Certified Semi-modular ATX About 18 months old. Motherboard BIOS :- Someone else was checking the BIOS. They said it was a Beta version. I discovered my RYZEN 5 5600x is the stepping 0 version of the CPU. Ram :- I don't know the make of the Ram - someone built the PC for me. 16GB DDR4-3200MHz RAM (2 x 8GB sticks, I understand Reboots :- Subsequent to those error messages, I tried a reboot. This failed :- The reboot error says: /dev/mapper/vgpiglit-root contains a file system with errors, check forced. Inodes that were a part of a corrupted orphan linked lost found. /dev/mapper/vgpiglit-root : UNEXPECTED INCONSISTENCY; RUN fsck manually.(i.e ., without -a or -p options). fsck exited with status code 4. The root filesystem on /dev/mapper/vgpiglit-root requires a manual fsck There is then a flashing prompt after "(initramfs)". The fsck command was then performed :- fsck -y /dev/mapper/vgpiglit-root A subsequent reboot worked. Firefox then had a very lengthy cursor lag, but this was solved by deleting the places and favicons data in the Firefox profile. No more error messages yet.
