RHEL 6 Storage Admin - 19.3. Configuring an Exported File System for Diskless Clients

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19.3. Configuring an Exported File System for Diskless Clients

The root directory of the exported file system (used by diskless clients in the network) is shared via NFS. Configure the NFS service to export the root directory by adding it to /etc/exports. For instructions on how to do so, refer to Section 10.6.1, “ The /etc/exports Configuration File”.

To accommodate completely diskless clients, the root directory should contain a complete Red Hat Enterprise Linux installation. You can synchronize this with a running system via rsync, as in:

rsync -a -e ssh --exclude='/proc/*' --exclude='/sys/*' hostname.com:/ /exported/root/directory

Replace hostname.com with the hostname of the running system with which to synchronize via rsync. The /exported/root/directory is the path to the exported file system.

Alternatively, you can also use yum with the --installroot option to install Red Hat Enterprise Linux to a specific location. For example:

yum groupinstall Base --installroot=/exported/root/directory

The file system to be exported still needs to be configured further before it can be used by diskless clients. To do this, perform the following procedure:

Configure the exported file system's /etc/fstab to contain (at least) the following configuration:

none          /tmp            tmpfs   defaults        0 0
tmpfs           /dev/shm        tmpfs   defaults        0 0
sysfs           /sys            sysfs   defaults        0 0
proc            /proc           proc    defaults        0 0

Select the kernel that diskless clients should use (vmlinuz-kernel-version) and copy it to the tftp boot directory:

cp /boot/vmlinuz-kernel-version /var/lib/tftpboot/
Create the initrd (i.e. initramfs-kernel-version.img) with network support:

dracut initramfs-kernel-version.img vmlinuz-kernel-version

Copy the resulting initramfs-kernel-version.img into the tftp boot directory as well.
Edit the default boot configuration to use the initrd and kernel inside /var/lib/tftpboot. This configuration should instruct the diskless client's root to mount the exported file system (/exported/root/directory) as read-write. To do this, configure /var/lib/tftpboot/pxelinux.cfg/default with the following:
```
default rhel6

label rhel6
  kernel vmlinuz-kernel-version
  append initrd=initramfs-kernel-version.img root=nfs:server-ip:/exported/root/directory rw
```
Replace server-ip with the IP address of the host machine on which the tftp and DHCP services reside.

The NFS share is now ready for exporting to diskless clients. These clients can boot over the network via PXE.