That's because linux supports only UFS1 mount write.
No, Linux supports UFS2 read/write just fine, it's just marked as EXPERIMENTAL in the kernel configuration. The configuration variables for Linux can be shown like this:
Code:
mls:~$ zcat /proc/config.gz | grep UFS
CONFIG_UFS_FS=y
CONFIG_UFS_FS_WRITE=y
# CONFIG_UFS_DEBUG is not set
Note that it is EXPERIMENTAL for a reason, and judging from outside the box, Linux UFS2 write support doesn't update all the FS structures. So if you write to UFS2 from Linux, be sure to have FreeBSD
fsck
the partitions before using them, preferably with the
-y flag. In all cases I've seen,
fsck
updates the block counts that Linux didn't update, nothing more.
Still, having a shared junk partition would ultimately be a safer choice than having both systems write to the FreeBSD / over and over again. As much as "backups! backups! backups!" is a good motto, an accidental backup of a corrupted partition would probably be bad.