Contents

  1. Verify UFS support
  2. Mount
  3. Edit /etc/fstab
  4. Write support
  5. Remarks

Verify UFS support

To check whether your Linux kernel supports the UFS filesystem 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. 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

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.

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