> See > https://fedoraproject.org/wiki/LiveOS_image#Overlay_recovery THANK YOU. That was enormously helpful and saved my bacon big time. The lvm snapshot is active and the filesystem is back. For future reference what I actually did was find the cow dm device for the invalid lvm snapshot from dmsetup which was the device with the same name as the snapshot plus "-cow": # dmsetup status vg_root-lv_u01_dev: 0 4724490240 snapshot Invalid vg_root-lv_u01_dev-cow: 0 1048576000 linear Then I ran the command from that doc to set the valid bit: # echo $'\x01' | dd of=/dev/mapper/vg_root-lv_u01_dev-cow bs=1 count=1 seek=4 conv=notrunc 1+0 records in 1+0 records out 1 byte (1 B) copied, 2.9e-05 seconds, 34.5 kB/s Then I didn't know how to reload the dm state so I rebooted the machine. This caused a bit of a scare because loading the lvm volumes took about 30 minutes. I don't know why or what happened there. But it eventually did come up. Then I ran fsck a a few times, the third time it found no problems (the first time actually seemed to corrupt the filesystem!). So actually a few things didn't work as expected. Firstly the lvm snapshot expiring actually made one of the pv's in the vg invalid: --- Physical volume --- PV Name unknown device VG Name vg_root This caused a lot of confusion since it looked like a hardware problem. There were no hardware errors and after rebooting that device seems fine so I think this was caused by dm. Then rebooting after the bit was twiddled rebooting froze for a very long time on this step in the redhat boot process: Setting up Logical Volume Management: It was about 30 minutes before this appeared: Setting up Logical Volume Management: 4 logical volume(s) in volume group "vg_root" I don't know what could possibly have caused that. It wasn't even mounting anything at this stage. I actually went for a drink at this point sure that I had corrupted the snapshot data structures in some weird way. One catch is I had done lvextend already -- does the snapshot dm need to initialize all the blocks of the newly extended cow table? -- greg -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
