down (305B)
1 # umount all filesystems except specials, if possible 2 foreground { umount --all --verbose --detach-loop -t nodevtmpfs,noproc,nosysfs,nodevpts,nomqueue } 3 # remount the rest read-only, except for tmpfs 4 foreground { umount --all --read-only --verbose -t nodevtmpfs,noproc,nosysfs,nodevpts,nomqueue,notmpfs }