Do you need to dismount /usr to dump it?

[Svein Halvor Halvorsen]

[Matt Staroscik, 2004-11-09]
>  If I boot to single-user mode (reboot, hit space, do boot -s) and dump /usr
>  to a file, I get read errors on a couple of blocks.
:
>  I thought it was safe to dump /usr in single-user mode. Will I need to boot
>  off a CD or try another trick to get a clean dump of /usr? Or perhaps I am
>  not using the right fsck options?


You do not mention which version you are running, but if you're running 
5.x and the /usr-partition has a ufs2 filsystem, you could use the -L 
option to make a dump of a 'live filesystem'

Dump will then make a snapshot of the filsystem, dump that, and then 
delete the snapshot. The dump will then be consistent, and as the disk 
were immideately after issuing the dump command.


Se more on dump(8), mksnap_ffs(8), mount(8) and 
/usr/src/sys/ufs/ffs/README.snapshot