During a ufsrestore/installboot session while cloning a solaris 8 box I
found that I could no longer use the format command after restoing /
and getting the target machine to boot. I would get this error :

format unable to open /dev/tty

Format would just bomb after this and wouldn't display the drives.

I found a few posts here where people had the same problem but nobody
ever answered so at the risk of delurking . . .

In my case my box would always come up in maintenance (single user
mode) even though I wasn't explicitly telling it to (this was the main
clue). It turns out that the machine I made my ufsdump file from used
to have a secondary disksuite array which wasn't part of the slice I
ufsrestored but was still listed in /etc/vfstab. I commented out this
line in vfstab and rebooted in to non maintenance mode. Once I did this
I could run format again, recreate the disksuite drives and secondary
mirror using format, ufsrestore that array, and finally uncomment the
line in /etc/vfstab. Since the secondary array existed everything came
up fine and my clone was complete.

-M

PS
Sun has a knowledge base article on this but the site is currently
down. Oddly their site lets you search for error text and is pretty
good about returning results. Often though, you can't access those
results because the login piece of their website is down (this is
arguably more frustrating than Microsoft's site which simply fails to
return results). In MS's case though you can google MS error messages
and get results from MS's site that MS's search engine doesn't return
:-)