NFS-Root mini-HOWTO

4. Booting the workstation

4.1 Using a boot ROM

As I have not used such a beast myself yet, I can give you only the following tips (courtesy of Christian Leutloff <leutloff at sundancer.tng.oche.de>):

• You can't use ``normal'' boot ROMs.
• There is a netboot packet by Gero Kuhlmann, that provides for boot ROMs for Linux, and further information. netboot is available from the local Linux mirror, or as a Debian package (netboot-0.4).
• Read the documentation coming with your boot ROM carefully.
• You probably will have to enable the tftpd on the server, but this depends upon your boot ROM's way of loading the kernel.
• Any information on boot-ROM vendors of these Linux variety, mentioned above, as not everybody has access to PROM burner :( (especially in Europe, as I'm located there.) welcome, I'll include them then here.

4.2 Using a raw kernel disk

If you have exported the root filesystem with the correct name for the default naming and your NFS server is also the RARP server (which implies that the boxes are on the same subnet.), than you can just boot the kernel by cating it to a disk. (You have to set the root device in the kernel to 0:255.) This assumes, that the root directory on the server is /tftpboot/IP Address (this value can be changed when compiling the kernel.)

4.3 Using a bootloader & RARP

Give the kernel all needed parameters when booting, and add nfsroot=<server-ip-addr>:</path/to/mount> where server-ip-addr is the IP address of your NFS-server, and /path/to/mount is the path to the root directory.

Tips:

• When using LILO consider using the ``lock'' feature: Simply type in once all the correct parameters and add ``lock''. Next time when booting let LILO timeout.
• When generating a workstation specific boot disk, you can also use the append= feature in lilo.conf.

4.4 Using a bootloader without RARP

The ip and nfsroot kernel parameters (which can be hardcoded into the kernel, interactively entered at some bootloader prompts, or included in lilo.conf via the append= parameter; see the next subsection) provide all of the information necessary for the client to set up its ethernet interface and to contact the NFS server, respectively. The parameters are fully documented in Documentation/nfsroot.txt, which is included in the kernel sources (usually found under /usr/src/linux). Here's the format for a machine with a static (pre-assigned) IP address:

• nfsroot=<NFS-server-IP-number>:/path/on/server/to/nfs_root ip=<client-IP-number>::<gateway-IP-number>:<netmask>:<client-hostname>:eth0:off

DHCP is much simpler:

• nfsroot=<NFS-server-IP-number>:/path/on/server/to/nfs_root ip=dhcp

4.5 Sample kernel command lines

Here's an example of a complete kernel command line such as you might include in lilo.conf or equivalent; only the IP numbers and NFS path are bogus:

• root=/dev/nfs rw nfsroot=12.345.67.89:/path/on/server/to/nfs_root ip=dhcp console=ttyS1

That uses DHCP to assign an IP address to the machine and puts its boot messages (console) on the second serial port. The following is the corresponding example using a static IP address; it also explicitly specifies Busybox's (non-standard) location for init:

• root=/dev/nfs rw nfsroot=12.345.67.89:/path/on/server/to/nfs_root ip=12.345.67.88::12.345.67.1:255.255.255.0:embed-o-matic:eth0:off console=ttyS1 init=/bin/init