Running diskless Fedora via iSCSI

If you have a diskless machine and want it to boot and run your favourite distro over network, you have several options how to achieve it.

In my case the machine was a rather small one, with slow CPU and little RAM, therefore I could not run anaconda on it. NFS can not be swapped on, therefore I used a iSCSI target to swap on, and also placed the root filestem image on iSCSI.

This article describes how to create a filesystem image that can be used for network booting painlessly and how to boot it.

Server setup

iSCSI target

You need to run an iSCSI target on the server. In Fedora, you have several choices of the target software. User-space based solution that are available netbsd-iscsi and scsi-target. All should work equally well. I chose a kernel-based solution, IET, that is available from Livna repository in iscsitarget package. It depends on kernel module, kmod-iscsitarget.

This is what my configuration in /etc/ietd.conf looks like:

  Target iqn.2008-02.lan:target0
          Lun 0 Path=/var/local/diskless-root
          MaxConnections 1

  Target iqn.2008-02.lan:target1
          Lun 0 Path=/var/local/diskless-swap
          MaxConnections 1

Before you start the iscsi-target service, be sure to create the images. Files with holes are perfectly ok and will occupy virtually no space when they are created:

  # dd if=/dev/zero of=/var/local/diskless-root bs=1k count=0 seek=5M
  # dd if=/dev/zero of=/var/local/diskless-swap bs=1k count=0 seek=512k

Now you can fire up the service.

  # service iscsi-target start

Network boot

You need just two things:

1. DHCP server
2. TFTP server with images for boot

For the former, you need the dhcp package. The latter consist of tftp-server package, pxelinux from syslinux package, kernel you'll copy from the client filesystem tree once it's created and ramdisk once it's generated. you'll have to copy the client kernel and the ramdisk to the boot server

Network boot setup is documented in various places in more detail. Search the Internets!

Installing the client image

Now move to your workstation. You need iscsi-initiator-utils there and iscsi service running. Log in to the iSCSI targets, create root partition and the filesytem.

  # iscsiadm -m discovery -t st -p server-address
  # iscsiadm -m node --login

Unless you've added some cool udev rules, you need to kind of guess which /dev/sd* device is your iSCSI target for the root filesystem. Probably dmesg or /proc/partitions are your friends while identifying.

  # fdisk /dev/sdb
  (...create at least one partition, for root...)
  # mke2fs -j -L diskless-root /dev/sdb1
  # mkswap -L diskless-swap /dev/sdc

Now we can start installing the operating system. You need anaconda. Having a mirror with Fedora tree will come handy

  # mount LABEL=diskless-root /mnt
  # anaconda -G -r /mnt -m http://mirror-address/fedora/linux/development/i386/os/

Once finished, update the target fstab and generate an inital ram disk image.

  # cat >>/etc/fstab <<EOF
  LABEL=diskless-root   /       ext3    relatime        1 1
  LABEL=diskless-swap   swap    swap    defaults        0 0
  EOF
  # mkinitrd -v --preload=crc32c                        \
        --fstab=/mnt/etc/fstab                          \
        --rootfs ext3 --rootdev=LABEL=diskless-root     \
        --with=via-rhine --with=sis900                  \
        initrd-image $(uname -r)

Note the following:

• --with=via-rhine --with=sis900 should be replaced with the module for your actual network card
• --preload=crc32c is here due to a known bug. It is needed by iSCSI initiator

Copy kernel from /mnt/boot, and the initrd-image to the TFTP server and you can safely unmount your target image.

  # umount LABEL=diskless-root

Log off the targets and you boot up your client. Good luck!

First published

Wed Feb 27 11:45:59 2008

Last changed

Thu Mar 27 22:37:38 2008

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