**Contents** [[!toc]] # Verify UFS support To check whether your Linux kernel supports the [UFS filesystem](http://en.wikipedia.org/wiki/Unix_File_System) you may execute the following command: $ cat /proc/filesystems nodev sysfs nodev rootfs nodev proc . . . ext3 nodev usbfs vfat **ufs** The keyword `nodev` in the first column means that filesystem does not require a block device to be mounted, that's why it is also called [virtual filesystem](http://en.wikipedia.org/wiki/Virtual_file_system). The support is either compiled inside the kernel or as a module: $ ls -l /lib/modules/2.6.21-ARCH/kernel/fs/ufs/ufs.ko -rw-r--r-- 1 root root 84828 2007-05-25 20:11 /lib/modules/2.6.21-ARCH/kernel/fs/ufs/ufs.ko # Mount In order to find the device that corresponds to your FFS partition, run: 1. sfdisk -l 
    
Disk /dev/hda: 155061 cylinders, 16 heads, 63 sectors/track
Warning: extended partition does not start at a cylinder boundary.
DOS and Linux will interpret the contents differently.
Units = cylinders of 516096 bytes, blocks of 1024 bytes, counting from 0
  Device Boot Start     End   #cyls    #blocks   Id  System
/dev/hda1   *      0+  34536-  34537-  17406396    7  HPFS/NTFS
			   end: (c,h,s) expected (1023,15,63) found (1023,254,63)
/dev/hda2      34536+ 134767- 100231-  50516392+   f  W95 Ext'd (LBA)
			   start: (c,h,s) expected (1023,15,63) found (1023,255,63)
			   end: (c,h,s) expected (1023,15,63) found (1023,254,63)
/dev/hda3     134767+ 144935-  10169-   5124735   a5  FreeBSD
			   start: (c,h,s) expected (1023,15,63) found (1023,255,63)
			   end: (c,h,s) expected (1023,15,63) found (1023,254,63)
/dev/hda4     144935+ 155060   10126-   5103189   a9  NetBSD
			   start: (c,h,s) expected (1023,15,63) found (1023,255,63)
			   end: (c,h,s) expected (1023,15,63) found (1023,80,63)
/dev/hda5      34536+ 102366-  67830-  34186288+  83  Linux
			   start: (c,h,s) expected (1023,15,63) found (0,1,1)
			   end: (c,h,s) expected (1023,15,63) found (1023,254,63)
/dev/hda6     102366+ 104294    1929-    971901   82  Linux swap / Solaris
			   start: (c,h,s) expected (1023,15,63) found (0,1,1)
			   end: (c,h,s) expected (1023,15,63) found (120,254,63)
/dev/hda7     104295+ 134767-  30473-  15358108+  83  Linux
			   start: (c,h,s) expected (1023,15,63) found (0,1,1)
			   end: (c,h,s) expected (1023,15,63) found (1023,254,63)
/dev/hda8     134767+ 143910-   9143-   4608000
/dev/hda9     143910+ 144935-   1026-    516735
/dev/hda10    144935+ 154078-   9143    4608072
/dev/hda11    154078+ 155060     983-    495117
/dev/hda12         0+  34536-  34537-  17406396
/dev/hda13     34536+ 102366-  67830-  34186288+
/dev/hda14    102366+ 104294    1929-    971901
/dev/hda15    104295+ 144935-  40641-  20482843+
So for FreeBSD (FFSv2), we have `/dev/hda3` which is equivalent to `/dev/ad0s3` And for NetBSD (FFSv1), we have `/dev/hda4` which is equivalent to `/dev/wd0c` But these devices are whole BSD slices (BIOS partitions), not BSD partitions. By examinating carefully sfdisk - l output, we find that: `/dev/hda3` (134767+,144935-) includes `/dev/hda8` (134767+,143910-) and `/dev/hda9` (143910+,144935-) `/dev/hda4` (144935+,155060) includes `/dev/hda10` (144935+,154078-) and `/dev/hda11` (154078+,155060) And we may deduce that for FreeBSD: `/dev/hda8` is equivalent to `/dev/ad0s3a` (FreeBSD root partition) `/dev/hda9` is equivalent to `/dev/ad0s3b` (FreeBSD swap) And for NetBSD: `/dev/hda10` is equivalent to `/dev/wd0a` (NetBSD root partition) `/dev/hda11` is equivalent to `/dev/wd0b` (NetBSD swap) Thus FreeBSD root partition lies at /dev/hda8. First create a directory to mount FFS partition and then mount it: # mkdir /mnt/freebsd # mount -t ufs -o ro,ufstype=ufs2 /dev/hda8 /mnt/freebsd/ And NetBSD root partition lies at `/dev/hda10`. First create a directory to mount FFS partition and then mount it: # mkdir /mnt/netbsd # mount -t ufs -o ro,ufstype=44bsd /dev/hda10 /mnt/netbsd/ Let's browse it: # ls /mnt/*bsd /mnt/freebsd: bin cdrom COPYRIGHT dist etc lib media proc root sys usr boot compat dev entropy home libexec mnt rescue sbin tmp var /mnt/netbsd: altroot etc gnome-screensave.core mnt root var bin GENERIC kern netbsd sbin boot GENERIC-DIAGNOSTIC lib onetbsd stand CUSTOM GENERIC-LAPTOP libdata proc tmp dev GENERIC-NOACPI libexec rescue usr # Edit /etc/fstab Add the following line to your `/etc/fstab` file: /dev/hda8 /mnt/freebsd ufs ufstype=ufs2,ro 0 2 /dev/hda10 /mnt/netbsd ufs ufstype=44bsd,ro 0 2 Now you can mount the FFS partitions by typing: # mount /mnt/freebsd # mount /mnt/netbsd and verify with: $ mount [...] /dev/hda8 on /mnt/freebsd type ufs (ro,ufstype=ufs2) /dev/hda10 on /mnt/netbsd type ufs (ro,ufstype=44bsd) [...] # Write support Write support is available given several conditions are satisfied: - ufs write support option compiled in Linux kernel (`CONFIG_UFS_FS_WRITE=y`): it is disabled by default. - FFSv1 filesystem (FFSv2 not yet supported) Please note that as I do not really need write support on NetBSD partitions from GNU/Linux, I did not bother to rebuild my Linux kernel and hence have not tested this feature. # Remarks * If you forget the `ro` option, you will get the following message at dmesg: $ dmesg | grep ufs ufs was compiled with read-only support, can't be mounted as read-write * If you forget to set the `ufstype` option, you will get the following message at dmesg: $ dmesg | grep ufstype mount -t ufs -o ufstype=sun|sunx86|44bsd|ufs2|5xbsd|old|hp|nextstep|nextstep-cd|openstep ... >>>WARNING<<< Wrong ufstype may corrupt your filesystem, default is ufstype=old So, extra care should be taken. People have reported crashes using FFS partitions access under GNU/Linux (even in read-only mode, that is very strange). I am half convinced that has been caused by accessing a whole BSD slice (BSD dedicated BIOS partition) instead of a BSD partition.