To enable multipath support during installation use
install disk-detect/multipath/enable=true
at the installer prompt. If multipath devices are found these will show up as /dev/mapper/mpath<X> during installation.
Old and deprecacted information
/!\ grub2 has had multipath support since 1.99-12 (Debian 7, wheezy). All information below this point only applies to Debian versions older then that.
In order to test Multipath in d-i you still need a patched grub (442382) but see below.
Installing Grub Legacy
Since neither Debian's grub nor grub2 support multipath device names yet (483971), you have to manually install a patch grub legacy (442382) during installation. A prebuilt deb for i386 is available here. (In case you need to built for another architecture, the sources are available via this git tree).
Method 1
Proceed with the installation until the installer asks you if you want to install grub on the multipath device then:
- switch to the second VT using CTRL-ALT-F2.
- copy the patched grub to /target/tmp
- chroot /target dpkg -i /tmp/grub_*.deb
- switch back to the first VT using CTRL-ALT-F1 and continue with the installation.
Method 2
This method works if you're installing via a serial console and can't switch VTs. Finish the installation until you're asked to reboot. Then:
hit cancel and head back to the main menu
- spawn a shell in d-i.
copy the patched grub deb to /target/tmp.
- then do:
chroot /target dpkg -i /tmp/grub*deb echo "(hd0) /dev/mapper/mpath0" > /boot/grub/device.map grub --device-map=/boot/grub/device.map
assuming your root filesystem is the first partition on the first multipath device (/dev/mapper/mpath0-part1) enter at the grub prompt:
root (hd0,0) setup (hd0) quit
- this should complete without errors
close the shell (CTRL-D)
- reboot the system
Multipath Support in Debian Installer:
Squeeze
These are the know open issues for Squeeze, please test and provide feedback:
grub: correctly detect multipath partitions (442382) - patch for grub-legacy needs to be updated for grub2
multipath-tools >= 0.4.8+git0.761c66f-4 (currently in unstable) due to changes in udev and kernel (575902).
Lenny
This needed/needs to be done to support multipathing natively in DebianInstaller:
libaio udeb (440320) - done
multipath udeb (440334) - done
kernel-wedge needs to support multipath-modules (439410) - done
linux-kernel-di-i386 needs to include multipath-modules (440447) - done
hw-detect: disk-detect.sh needs to pull in /sbin/multipath and the necessary kernel modules. If there are multipath devices we need to also pull in partman-multipath. (440439) - done
parted: correctly identify multipath devices (440675) - done
partman-base (442236) - done:
- needs to skip block devices that are part of a multipath device (part_of_multipath())
- humandev() needs multipath support
- move all helper functions for the other modules to identify multipath devices here
partman-multipath (added to d-i svn) - done:
- mark devices as multipath
- call kpartx to create the partition mappings
grub: correctly detect multipath partitions (442382) - patch for grub-legacy needs to be updated for grub2
partman-auto: don't skip multipath devices - (468799) - done
grub-installer needs the same patch as grub's grub-install and furthermore mustn't treat mpath devices as LVM (468832) - done
- update the installer manual (TBD)
put up a for easy testing - done - you can use the official Lenny RC images