StatelessLinux/NFSRoot

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StatelessLinux - NFS Root

See Stateless Linux HOWTO

NOTE: Much of this is probably out of date now and it needs a complete review/revamp. Note that it also suggests modifying /etc/sysconfig/mkinitrd, which is wrong for a stateless environment.

This is probably the most straightforward way for stateless clients to use a root filesystem image which you have prepared.

Each client PXE boots (i.e. obtains the location of its bootloader via a DHCP request which in turn downloads a kernel and initrd using TFTP) and mounts its root filesystem over NFS.


Create An initrd

In order for the client to mount the NFS exported directory as its root filesystem, it must have an initrd which knows how to do it. The initrd must load the appropriate network card driver, initialise the device using DHCP and mount the root filesystem from the correct NFS server and export.

First, we mount the image and setup /tmp, /proc, /sys etc. for mkinitrd 

$> losetup /dev/loop0 ./terminal.img
$> mount -o ro /dev/loop0 nfs-export/
$> mount -t tmpfs none nfs-export/tmp
$> mount -t tmpfs none nfs-export/dev
$> mount -t tmpfs none nfs-export/var/lock
$> mount -t proc none nfs-export/proc
$> mount -t sysfs none nfs-export/sys

Next, in /etc/sysconfig/mkinitrd, configure the network device and driver modules which the clients will use: 

$> mount -o remount,rw nfs-export/
$> cat > /etc/sysconfig/mkinitrd << EOF
NET_LIST="eth0"
MODULES="e1000"
EOF
$> mount -o remount,ro nfs-export/

Now run mkinitrd: 

$> chroot nfs-export/ mkinitrd --rootdev 172.31.0.7:/stateless/terminal/nfs-export \
--rootfs nfs -f /tmp/initrd.img 2.6.17-1.2510.fc6
$> mv nfs-export/tmp/initrd.img .


Clean up after yourself: 

$> for dir in sys proc var/lock dev tmp; do umount nfs-export/$dir; done
$> umount nfs-export/
$> losetup -d /dev/loop0

Notes

Boot A Client

First, you need to make the appropriate kernel and initrd available to pxelinux and create a pxelinux config file pointing at them: 

$> cp vmlinuz initrd.img /tftpboot/linux-install
$> cat > /tftpboot/linux-install/pxelinux.cfg/default << EOF
default linux
kernel vmlinuz
append initrd=initrd.img selinux=0
EOF

Next, export the root filesystem over NFS: 

$> cat > /etc/exports << EOF
/stateless/terminal/nfs-export 172.31.0.0/24(ro,async,no_root_squash)
EOF
$> exportfs -r

Finally, configure the client's BIOS to boot via PXE and you should see it use DHCP to configure its NIC and obtain the location of pxelinux, download pxelinux using TFTP, download the pxelinux config file, downloaed and boot the kernel and initrd which will in turn mount the root filesystem over NFS.

Notes: 

def mac_address_to_filename (mac_address):
return "01-" + mac_address.lower ().replace (":", "-")


Boot With Xen

You can also boot a client with NFS root using Xen.

First, though, you need a different kernel and initrd:

Using xm: 

$> cat > ./Terminal.cfg << EOF
name = "Terminal"
memory = "512"
vif = [ "" ] 
kernel = "/stateless/terminal/vmlinuz"
ramdisk = "/stateless/terminal/initrd.img"
extra = "selinux=0"
EOF

Using libvirt: 

$> cat > ./Terminal.xml << EOF
<domain type='xen'>
<name>Terminal</name>
<os>
<type>linux</type>
<kernel>/redhat/stateless/terminal/vmlinuz</kernel>
<initrd>/redhat/stateless/terminal/initrd.img</initrd>
<cmdline>selinux=0</cmdline>
</os>
<memory>524288</memory>
<vcpu>1</vcpu>
<devices><interface/></devices>
</domain>
EOF
$> virsh create ./Terminal.xml
$> xm console Terminal

Notes:

Retrieved from "https://fedoraproject.org/wiki/StatelessLinux/NFSRoot"