FreeBSD HOWTO: Software Mirror System Disk

Danny Howard dannyman at
Mon Jan 24 12:25:01 PST 2005

Danny Howard wrote:

> As the documentation is a bit sketchy, here’s a quick cheat sheet for 
> setting this up with gmirror:
> (This crib sheet assumes you have a pair of identical IDE (in my case, 
> SATA) drives identified as ad4 and ad6.)

Let me apologize for Thunderbird formatting my mail goofy.  (I only use 
it for mailing lists, silly vim weenie.)  Here's a little clean-up:

      1. Install FreeBSD on to ad4.
      2. Reboot with the Install CD.
      3. Enter Fixit mode, using Install CD disc2 as the “live filesystem”
      4. # chroot /dist
         # mount_devfs devfs /dev
         # gmirror label -v -b round-robin gm0 /dev/ad4
         # gmirror insert gm0 /dev/ad6
         # mount /dev/mirror/gm0s1a /mnt
         # echo ‘geom_mirror_load="YES"‘ >> /mnt/boot/loader.conf
         # echo ’swapoff="YES"‘ >> /mnt/etc/rc.conf
      5. Edit /mnt/etc/fstab to convert ad4 -> mirror/gm0
      6. Reboot


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