Apparently, Knoppix cannot be used to write on UFS file system (Solaris).

It happened to me that one disk in a RAID 1 array failed and the array could not be restored. Therefore, I tried to modify /etc/vfstab using Knoppix on the remaining intact disk drive (with the vi editor). Knoppix crashed, and the /etc directory was destroyed. This was reproducible with a less critical directory.

The disk was mounted like this:

mount -t ufs -o ufstype=sun /dev/hdd1 /mnt/hdd1

and made writable with the Knoppix read/write toggle.