[linux-2.6-block.git] / Documentation / filesystems / nfs / nfsroot.txt

Mounting the root filesystem via NFS (nfsroot)
===============================================

Written 1996 by Gero Kuhlmann <gero@gkminix.han.de>
Updated 1997 by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
Updated 2006 by Nico Schottelius <nico-kernel-nfsroot@schottelius.org>
Updated 2006 by Horms <horms@verge.net.au>
Updated 2018 by Chris Novakovic <chris@chrisn.me.uk>


In order to use a diskless system, such as an X-terminal or printer server
for example, it is necessary for the root filesystem to be present on a
non-disk device. This may be an initramfs (see Documentation/filesystems/
ramfs-rootfs-initramfs.txt), a ramdisk (see Documentation/admin-guide/initrd.rst) or a
filesystem mounted via NFS. The following text describes on how to use NFS
for the root filesystem. For the rest of this text 'client' means the
diskless system, and 'server' means the NFS server.


1.) Enabling nfsroot capabilities
    -----------------------------

In order to use nfsroot, NFS client support needs to be selected as
built-in during configuration. Once this has been selected, the nfsroot
option will become available, which should also be selected.

In the networking options, kernel level autoconfiguration can be selected,
along with the types of autoconfiguration to support. Selecting all of
DHCP, BOOTP and RARP is safe.


2.) Kernel command line
    -------------------

When the kernel has been loaded by a boot loader (see below) it needs to be
told what root fs device to use. And in the case of nfsroot, where to find
both the server and the name of the directory on the server to mount as root.
This can be established using the following kernel command line parameters:


root=/dev/nfs

  This is necessary to enable the pseudo-NFS-device. Note that it's not a
  real device but just a synonym to tell the kernel to use NFS instead of
  a real device.


nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]

  If the `nfsroot' parameter is NOT given on the command line,
  the default "/tftpboot/%s" will be used.

  <server-ip>	Specifies the IP address of the NFS server.
		The default address is determined by the `ip' parameter
		(see below). This parameter allows the use of different
		servers for IP autoconfiguration and NFS.

  <root-dir>	Name of the directory on the server to mount as root.
		If there is a "%s" token in the string, it will be
		replaced by the ASCII-representation of the client's
		IP address.

  <nfs-options>	Standard NFS options. All options are separated by commas.
		The following defaults are used:
			port		= as given by server portmap daemon
			rsize		= 4096
			wsize		= 4096
			timeo		= 7
			retrans		= 3
			acregmin	= 3
			acregmax	= 60
			acdirmin	= 30
			acdirmax	= 60
			flags		= hard, nointr, noposix, cto, ac


ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
   <dns0-ip>:<dns1-ip>:<ntp0-ip>

  This parameter tells the kernel how to configure IP addresses of devices
  and also how to set up the IP routing table. It was originally called
  `nfsaddrs', but now the boot-time IP configuration works independently of
  NFS, so it was renamed to `ip' and the old name remained as an alias for
  compatibility reasons.

  If this parameter is missing from the kernel command line, all fields are
  assumed to be empty, and the defaults mentioned below apply. In general
  this means that the kernel tries to configure everything using
  autoconfiguration.

  The <autoconf> parameter can appear alone as the value to the `ip'
  parameter (without all the ':' characters before).  If the value is
  "ip=off" or "ip=none", no autoconfiguration will take place, otherwise
  autoconfiguration will take place.  The most common way to use this
  is "ip=dhcp".

  <client-ip>	IP address of the client.

  		Default:  Determined using autoconfiguration.

  <server-ip>	IP address of the NFS server. If RARP is used to determine
		the client address and this parameter is NOT empty only
		replies from the specified server are accepted.

		Only required for NFS root. That is autoconfiguration
		will not be triggered if it is missing and NFS root is not
		in operation.

		Value is exported to /proc/net/pnp with the prefix "bootserver "
		(see below).

		Default: Determined using autoconfiguration.
		         The address of the autoconfiguration server is used.

  <gw-ip>	IP address of a gateway if the server is on a different subnet.

		Default: Determined using autoconfiguration.

  <netmask>	Netmask for local network interface. If unspecified
		the netmask is derived from the client IP address assuming
		classful addressing.

		Default:  Determined using autoconfiguration.

  <hostname>	Name of the client. If a '.' character is present, anything
		before the first '.' is used as the client's hostname, and anything
		after it is used as its NIS domain name. May be supplied by
		autoconfiguration, but its absence will not trigger autoconfiguration.
		If specified and DHCP is used, the user-provided hostname (and NIS
		domain name, if present) will be carried in the DHCP request; this
		may cause a DNS record to be created or updated for the client.

  		Default: Client IP address is used in ASCII notation.

  <device>	Name of network device to use.

		Default: If the host only has one device, it is used.
			 Otherwise the device is determined using
			 autoconfiguration. This is done by sending
			 autoconfiguration requests out of all devices,
			 and using the device that received the first reply.

  <autoconf>	Method to use for autoconfiguration. In the case of options
                which specify multiple autoconfiguration protocols,
		requests are sent using all protocols, and the first one
		to reply is used.

		Only autoconfiguration protocols that have been compiled
		into the kernel will be used, regardless of the value of
		this option.

                  off or none: don't use autoconfiguration
				(do static IP assignment instead)
		  on or any:   use any protocol available in the kernel
			       (default)
		  dhcp:        use DHCP
		  bootp:       use BOOTP
		  rarp:        use RARP
		  both:        use both BOOTP and RARP but not DHCP
		               (old option kept for backwards compatibility)

		if dhcp is used, the client identifier can be used by following
		format "ip=dhcp,client-id-type,client-id-value"

                Default: any

  <dns0-ip>	IP address of primary nameserver.
		Value is exported to /proc/net/pnp with the prefix "nameserver "
		(see below).

		Default: None if not using autoconfiguration; determined
		automatically if using autoconfiguration.

  <dns1-ip>	IP address of secondary nameserver.
		See <dns0-ip>.

  <ntp0-ip>	IP address of a Network Time Protocol (NTP) server.
		Value is exported to /proc/net/ipconfig/ntp_servers, but is
		otherwise unused (see below).

		Default: None if not using autoconfiguration; determined
		automatically if using autoconfiguration.

  After configuration (whether manual or automatic) is complete, two files
  are created in the following format; lines are omitted if their respective
  value is empty following configuration:

  - /proc/net/pnp:

	#PROTO: <DHCP|BOOTP|RARP|MANUAL>	(depending on configuration method)
	domain <dns-domain>			(if autoconfigured, the DNS domain)
	nameserver <dns0-ip>			(primary name server IP)
	nameserver <dns1-ip>			(secondary name server IP)
	nameserver <dns2-ip>			(tertiary name server IP)
	bootserver <server-ip>			(NFS server IP)

  - /proc/net/ipconfig/ntp_servers:

	<ntp0-ip>				(NTP server IP)
	<ntp1-ip>				(NTP server IP)
	<ntp2-ip>				(NTP server IP)

  <dns-domain> and <dns2-ip> (in /proc/net/pnp) and <ntp1-ip> and <ntp2-ip>
  (in /proc/net/ipconfig/ntp_servers) are requested during autoconfiguration;
  they cannot be specified as part of the "ip=" kernel command line parameter.

  Because the "domain" and "nameserver" options are recognised by DNS
  resolvers, /etc/resolv.conf is often linked to /proc/net/pnp on systems
  that use an NFS root filesystem.

  Note that the kernel will not synchronise the system time with any NTP
  servers it discovers; this is the responsibility of a user space process
  (e.g. an initrd/initramfs script that passes the IP addresses listed in
  /proc/net/ipconfig/ntp_servers to an NTP client before mounting the real
  root filesystem if it is on NFS).


nfsrootdebug

  This parameter enables debugging messages to appear in the kernel
  log at boot time so that administrators can verify that the correct
  NFS mount options, server address, and root path are passed to the
  NFS client.


rdinit=<executable file>

  To specify which file contains the program that starts system
  initialization, administrators can use this command line parameter.
  The default value of this parameter is "/init".  If the specified
  file exists and the kernel can execute it, root filesystem related
  kernel command line parameters, including `nfsroot=', are ignored.

  A description of the process of mounting the root file system can be
  found in:

    Documentation/early-userspace/README


3.) Boot Loader
    ----------

To get the kernel into memory different approaches can be used.
They depend on various facilities being available:


3.1)  Booting from a floppy using syslinux

	When building kernels, an easy way to create a boot floppy that uses
	syslinux is to use the zdisk or bzdisk make targets which use zimage
      	and bzimage images respectively. Both targets accept the
     	FDARGS parameter which can be used to set the kernel command line.

	e.g.
	   make bzdisk FDARGS="root=/dev/nfs"

   	Note that the user running this command will need to have
     	access to the floppy drive device, /dev/fd0

     	For more information on syslinux, including how to create bootdisks
     	for prebuilt kernels, see http://syslinux.zytor.com/

	N.B: Previously it was possible to write a kernel directly to
	     a floppy using dd, configure the boot device using rdev, and
	     boot using the resulting floppy. Linux no longer supports this
	     method of booting.

3.2) Booting from a cdrom using isolinux

     	When building kernels, an easy way to create a bootable cdrom that
     	uses isolinux is to use the isoimage target which uses a bzimage
     	image. Like zdisk and bzdisk, this target accepts the FDARGS
     	parameter which can be used to set the kernel command line.

	e.g.
	  make isoimage FDARGS="root=/dev/nfs"

     	The resulting iso image will be arch/<ARCH>/boot/image.iso
     	This can be written to a cdrom using a variety of tools including
     	cdrecord.

	e.g.
	  cdrecord dev=ATAPI:1,0,0 arch/x86/boot/image.iso

     	For more information on isolinux, including how to create bootdisks
     	for prebuilt kernels, see http://syslinux.zytor.com/

3.2) Using LILO
	When using LILO all the necessary command line parameters may be
	specified using the 'append=' directive in the LILO configuration
	file.

	However, to use the 'root=' directive you also need to create
	a dummy root device, which may be removed after LILO is run.

	mknod /dev/boot255 c 0 255

	For information on configuring LILO, please refer to its documentation.

3.3) Using GRUB
	When using GRUB, kernel parameter are simply appended after the kernel
	specification: kernel <kernel> <parameters>

3.4) Using loadlin
	loadlin may be used to boot Linux from a DOS command prompt without
	requiring a local hard disk to mount as root. This has not been
	thoroughly tested by the authors of this document, but in general
	it should be possible configure the kernel command line similarly
	to the configuration of LILO.

	Please refer to the loadlin documentation for further information.

3.5) Using a boot ROM
	This is probably the most elegant way of booting a diskless client.
	With a boot ROM the kernel is loaded using the TFTP protocol. The
	authors of this document are not aware of any no commercial boot
	ROMs that support booting Linux over the network. However, there
	are two free implementations of a boot ROM, netboot-nfs and
	etherboot, both of which are available on sunsite.unc.edu, and both
	of which contain everything you need to boot a diskless Linux client.

3.6) Using pxelinux
	Pxelinux may be used to boot linux using the PXE boot loader
	which is present on many modern network cards.

	When using pxelinux, the kernel image is specified using
	"kernel <relative-path-below /tftpboot>". The nfsroot parameters
	are passed to the kernel by adding them to the "append" line.
	It is common to use serial console in conjunction with pxeliunx,
	see Documentation/admin-guide/serial-console.rst for more information.

	For more information on isolinux, including how to create bootdisks
	for prebuilt kernels, see http://syslinux.zytor.com/


4.) Credits
    -------

  The nfsroot code in the kernel and the RARP support have been written
  by Gero Kuhlmann <gero@gkminix.han.de>.

  The rest of the IP layer autoconfiguration code has been written
  by Martin Mares <mj@atrey.karlin.mff.cuni.cz>.

  In order to write the initial version of nfsroot I would like to thank
  Jens-Uwe Mager <jum@anubis.han.de> for his help.
Commit	Line	Data
1da177e4 LT	1	Mounting the root filesystem via NFS (nfsroot)
	2	===============================================
	3
	4	Written 1996 by Gero Kuhlmann <gero@gkminix.han.de>
	5	Updated 1997 by Martin Mares <mj@atrey.karlin.mff.cuni.cz>
7e9dd124	6	Updated 2006 by Nico Schottelius <nico-kernel-nfsroot@schottelius.org>
64552a50	7	Updated 2006 by Horms <horms@verge.net.au>
c04d2cb2	8	Updated 2018 by Chris Novakovic <chris@chrisn.me.uk>
1da177e4 LT	9
	10
	11
64552a50 H	12	In order to use a diskless system, such as an X-terminal or printer server
	13	for example, it is necessary for the root filesystem to be present on a
	14	non-disk device. This may be an initramfs (see Documentation/filesystems/
8c27ceff	15	ramfs-rootfs-initramfs.txt), a ramdisk (see Documentation/admin-guide/initrd.rst) or a
64552a50 H	16	filesystem mounted via NFS. The following text describes on how to use NFS
64552a50 H	17	for the root filesystem. For the rest of this text 'client' means the
1da177e4 LT	18	diskless system, and 'server' means the NFS server.
	19
	20
	21
	22
	23	1.) Enabling nfsroot capabilities
	24	-----------------------------
	25
64552a50 H	26	In order to use nfsroot, NFS client support needs to be selected as
	27	built-in during configuration. Once this has been selected, the nfsroot
	28	option will become available, which should also be selected.
	29
	30	In the networking options, kernel level autoconfiguration can be selected,
	31	along with the types of autoconfiguration to support. Selecting all of
	32	DHCP, BOOTP and RARP is safe.
1da177e4 LT	33
	34
	35
	36
	37	2.) Kernel command line
	38	-------------------
	39
64552a50 H	40	When the kernel has been loaded by a boot loader (see below) it needs to be
	41	told what root fs device to use. And in the case of nfsroot, where to find
	42	both the server and the name of the directory on the server to mount as root.
	43	This can be established using the following kernel command line parameters:
1da177e4 LT	44
	45
	46	root=/dev/nfs
	47
	48	This is necessary to enable the pseudo-NFS-device. Note that it's not a
	49	real device but just a synonym to tell the kernel to use NFS instead of
	50	a real device.
	51
	52
	53	nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
	54
64552a50 H	55	If the `nfsroot' parameter is NOT given on the command line,
64552a50 H	56	the default "/tftpboot/%s" will be used.
1da177e4	57
64552a50 H	58	<server-ip> Specifies the IP address of the NFS server.
	59	The default address is determined by the `ip' parameter
	60	(see below). This parameter allows the use of different
	61	servers for IP autoconfiguration and NFS.
1da177e4	62
64552a50 H	63	<root-dir> Name of the directory on the server to mount as root.
	64	If there is a "%s" token in the string, it will be
	65	replaced by the ASCII-representation of the client's
	66	IP address.
1da177e4 LT	67
1da177e4 LT	68	<nfs-options> Standard NFS options. All options are separated by commas.
64552a50	69	The following defaults are used:
1da177e4	70	port = as given by server portmap daemon
91dd26ad DA	71	rsize = 4096
91dd26ad DA	72	wsize = 4096
1da177e4 LT	73	timeo = 7
	74	retrans = 3
	75	acregmin = 3
	76	acregmax = 60
	77	acdirmin = 30
	78	acdirmax = 60
	79	flags = hard, nointr, noposix, cto, ac
	80
	81
5e953778	82	ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
c04d2cb2	83	<dns0-ip>:<dns1-ip>:<ntp0-ip>
1da177e4 LT	84
1da177e4 LT	85	This parameter tells the kernel how to configure IP addresses of devices
64552a50 H	86	and also how to set up the IP routing table. It was originally called
	87	`nfsaddrs', but now the boot-time IP configuration works independently of
	88	NFS, so it was renamed to `ip' and the old name remained as an alias for
	89	compatibility reasons.
1da177e4 LT	90
	91	If this parameter is missing from the kernel command line, all fields are
	92	assumed to be empty, and the defaults mentioned below apply. In general
64552a50 H	93	this means that the kernel tries to configure everything using
	94	autoconfiguration.
	95
	96	The <autoconf> parameter can appear alone as the value to the `ip'
f33e1d9f AW	97	parameter (without all the ':' characters before). If the value is
	98	"ip=off" or "ip=none", no autoconfiguration will take place, otherwise
	99	autoconfiguration will take place. The most common way to use this
	100	is "ip=dhcp".
	101
64552a50	102	<client-ip> IP address of the client.
1da177e4	103
64552a50	104	Default: Determined using autoconfiguration.
1da177e4 LT	105
	106	<server-ip> IP address of the NFS server. If RARP is used to determine
	107	the client address and this parameter is NOT empty only
64552a50 H	108	replies from the specified server are accepted.
64552a50 H	109
411c9403	110	Only required for NFS root. That is autoconfiguration
64552a50 H	111	will not be triggered if it is missing and NFS root is not
	112	in operation.
	113
8b0b37c5 CN	114	Value is exported to /proc/net/pnp with the prefix "bootserver "
	115	(see below).
	116
64552a50 H	117	Default: Determined using autoconfiguration.
	118	The address of the autoconfiguration server is used.
	119
	120	<gw-ip> IP address of a gateway if the server is on a different subnet.
	121
	122	Default: Determined using autoconfiguration.
	123
	124	<netmask> Netmask for local network interface. If unspecified
1da177e4	125	the netmask is derived from the client IP address assuming
64552a50	126	classful addressing.
1da177e4	127
64552a50	128	Default: Determined using autoconfiguration.
1da177e4	129
660de409 CN	130	<hostname> Name of the client. If a '.' character is present, anything
	131	before the first '.' is used as the client's hostname, and anything
	132	after it is used as its NIS domain name. May be supplied by
	133	autoconfiguration, but its absence will not trigger autoconfiguration.
	134	If specified and DHCP is used, the user-provided hostname (and NIS
	135	domain name, if present) will be carried in the DHCP request; this
	136	may cause a DNS record to be created or updated for the client.
1da177e4	137
64552a50	138	Default: Client IP address is used in ASCII notation.
1da177e4	139
64552a50 H	140	<device> Name of network device to use.
	141
	142	Default: If the host only has one device, it is used.
	143	Otherwise the device is determined using
	144	autoconfiguration. This is done by sending
	145	autoconfiguration requests out of all devices,
	146	and using the device that received the first reply.
1da177e4	147
64552a50 H	148	<autoconf> Method to use for autoconfiguration. In the case of options
	149	which specify multiple autoconfiguration protocols,
	150	requests are sent using all protocols, and the first one
	151	to reply is used.
1da177e4	152
64552a50 H	153	Only autoconfiguration protocols that have been compiled
	154	into the kernel will be used, regardless of the value of
	155	this option.
1da177e4	156
f33e1d9f	157	off or none: don't use autoconfiguration
92ffb85d	158	(do static IP assignment instead)
64552a50	159	on or any: use any protocol available in the kernel
a6c05c3d	160	(default)
64552a50 H	161	dhcp: use DHCP
	162	bootp: use BOOTP
	163	rarp: use RARP
	164	both: use both BOOTP and RARP but not DHCP
	165	(old option kept for backwards compatibility)
1da177e4	166
26fb342c LR	167	if dhcp is used, the client identifier can be used by following
	168	format "ip=dhcp,client-id-type,client-id-value"
	169
64552a50	170	Default: any
1da177e4	171
8b0b37c5 CN	172	<dns0-ip> IP address of primary nameserver.
	173	Value is exported to /proc/net/pnp with the prefix "nameserver "
	174	(see below).
	175
	176	Default: None if not using autoconfiguration; determined
	177	automatically if using autoconfiguration.
	178
	179	<dns1-ip> IP address of secondary nameserver.
	180	See <dns0-ip>.
	181
c04d2cb2 CN	182	<ntp0-ip> IP address of a Network Time Protocol (NTP) server.
	183	Value is exported to /proc/net/ipconfig/ntp_servers, but is
	184	otherwise unused (see below).
	185
	186	Default: None if not using autoconfiguration; determined
	187	automatically if using autoconfiguration.
	188
	189	After configuration (whether manual or automatic) is complete, two files
	190	are created in the following format; lines are omitted if their respective
	191	value is empty following configuration:
	192
	193	- /proc/net/pnp:
8b0b37c5 CN	194
	195	#PROTO: <DHCP\|BOOTP\|RARP\|MANUAL> (depending on configuration method)
	196	domain <dns-domain> (if autoconfigured, the DNS domain)
	197	nameserver <dns0-ip> (primary name server IP)
	198	nameserver <dns1-ip> (secondary name server IP)
	199	nameserver <dns2-ip> (tertiary name server IP)
	200	bootserver <server-ip> (NFS server IP)
	201
c04d2cb2 CN	202	- /proc/net/ipconfig/ntp_servers:
	203
	204	<ntp0-ip> (NTP server IP)
	205	<ntp1-ip> (NTP server IP)
	206	<ntp2-ip> (NTP server IP)
	207
	208	<dns-domain> and <dns2-ip> (in /proc/net/pnp) and <ntp1-ip> and <ntp2-ip>
	209	(in /proc/net/ipconfig/ntp_servers) are requested during autoconfiguration;
	210	they cannot be specified as part of the "ip=" kernel command line parameter.
5e953778	211
8b0b37c5 CN	212	Because the "domain" and "nameserver" options are recognised by DNS
	213	resolvers, /etc/resolv.conf is often linked to /proc/net/pnp on systems
	214	that use an NFS root filesystem.
5e953778	215
c04d2cb2 CN	216	Note that the kernel will not synchronise the system time with any NTP
	217	servers it discovers; this is the responsibility of a user space process
	218	(e.g. an initrd/initramfs script that passes the IP addresses listed in
	219	/proc/net/ipconfig/ntp_servers to an NTP client before mounting the real
	220	root filesystem if it is on NFS).
	221
1da177e4	222
306a0753 CL	223	nfsrootdebug
	224
	225	This parameter enables debugging messages to appear in the kernel
	226	log at boot time so that administrators can verify that the correct
	227	NFS mount options, server address, and root path are passed to the
	228	NFS client.
	229
	230
	231	rdinit=<executable file>
	232
	233	To specify which file contains the program that starts system
	234	initialization, administrators can use this command line parameter.
	235	The default value of this parameter is "/init". If the specified
	236	file exists and the kernel can execute it, root filesystem related
	237	kernel command line parameters, including `nfsroot=', are ignored.
	238
	239	A description of the process of mounting the root file system can be
	240	found in:
	241
	242	Documentation/early-userspace/README
	243
	244
1da177e4	245
1da177e4	246
64552a50 H	247	3.) Boot Loader
64552a50 H	248	----------
1da177e4	249
64552a50 H	250	To get the kernel into memory different approaches can be used.
64552a50 H	251	They depend on various facilities being available:
1da177e4	252
1da177e4	253
64552a50	254	3.1) Booting from a floppy using syslinux
1da177e4	255
64552a50	256	When building kernels, an easy way to create a boot floppy that uses
1c828320	257	syslinux is to use the zdisk or bzdisk make targets which use zimage
64552a50 H	258	and bzimage images respectively. Both targets accept the
64552a50 H	259	FDARGS parameter which can be used to set the kernel command line.
1da177e4	260
64552a50 H	261	e.g.
	262	make bzdisk FDARGS="root=/dev/nfs"
	263
	264	Note that the user running this command will need to have
	265	access to the floppy drive device, /dev/fd0
	266
	267	For more information on syslinux, including how to create bootdisks
	268	for prebuilt kernels, see http://syslinux.zytor.com/
	269
	270	N.B: Previously it was possible to write a kernel directly to
	271	a floppy using dd, configure the boot device using rdev, and
	272	boot using the resulting floppy. Linux no longer supports this
	273	method of booting.
	274
	275	3.2) Booting from a cdrom using isolinux
	276
	277	When building kernels, an easy way to create a bootable cdrom that
	278	uses isolinux is to use the isoimage target which uses a bzimage
	279	image. Like zdisk and bzdisk, this target accepts the FDARGS
	280	parameter which can be used to set the kernel command line.
	281
	282	e.g.
	283	make isoimage FDARGS="root=/dev/nfs"
	284
	285	The resulting iso image will be arch/<ARCH>/boot/image.iso
	286	This can be written to a cdrom using a variety of tools including
	287	cdrecord.
	288
	289	e.g.
25eb650a	290	cdrecord dev=ATAPI:1,0,0 arch/x86/boot/image.iso
64552a50 H	291
	292	For more information on isolinux, including how to create bootdisks
	293	for prebuilt kernels, see http://syslinux.zytor.com/
1da177e4	294
1da177e4	295	3.2) Using LILO
64552a50 H	296	When using LILO all the necessary command line parameters may be
	297	specified using the 'append=' directive in the LILO configuration
	298	file.
	299
	300	However, to use the 'root=' directive you also need to create
	301	a dummy root device, which may be removed after LILO is run.
	302
	303	mknod /dev/boot255 c 0 255
	304
	305	For information on configuring LILO, please refer to its documentation.
1da177e4	306
7e9dd124	307	3.3) Using GRUB
64552a50 H	308	When using GRUB, kernel parameter are simply appended after the kernel
64552a50 H	309	specification: kernel <kernel> <parameters>
7e9dd124 NS	310
7e9dd124 NS	311	3.4) Using loadlin
64552a50 H	312	loadlin may be used to boot Linux from a DOS command prompt without
	313	requiring a local hard disk to mount as root. This has not been
	314	thoroughly tested by the authors of this document, but in general
	315	it should be possible configure the kernel command line similarly
	316	to the configuration of LILO.
	317
	318	Please refer to the loadlin documentation for further information.
1da177e4	319
7e9dd124	320	3.5) Using a boot ROM
64552a50 H	321	This is probably the most elegant way of booting a diskless client.
	322	With a boot ROM the kernel is loaded using the TFTP protocol. The
	323	authors of this document are not aware of any no commercial boot
	324	ROMs that support booting Linux over the network. However, there
	325	are two free implementations of a boot ROM, netboot-nfs and
	326	etherboot, both of which are available on sunsite.unc.edu, and both
	327	of which contain everything you need to boot a diskless Linux client.
1da177e4	328
7e9dd124	329	3.6) Using pxelinux
64552a50 H	330	Pxelinux may be used to boot linux using the PXE boot loader
	331	which is present on many modern network cards.
	332
	333	When using pxelinux, the kernel image is specified using
7e9dd124 NS	334	"kernel <relative-path-below /tftpboot>". The nfsroot parameters
7e9dd124 NS	335	are passed to the kernel by adding them to the "append" line.
64552a50	336	It is common to use serial console in conjunction with pxeliunx,
8c27ceff	337	see Documentation/admin-guide/serial-console.rst for more information.
64552a50 H	338
	339	For more information on isolinux, including how to create bootdisks
	340	for prebuilt kernels, see http://syslinux.zytor.com/
7e9dd124	341
1da177e4 LT	342
	343
	344
	345	4.) Credits
	346	-------
	347
	348	The nfsroot code in the kernel and the RARP support have been written
	349	by Gero Kuhlmann <gero@gkminix.han.de>.
	350
	351	The rest of the IP layer autoconfiguration code has been written
	352	by Martin Mares <mj@atrey.karlin.mff.cuni.cz>.
	353
	354	In order to write the initial version of nfsroot I would like to thank
	355	Jens-Uwe Mager <jum@anubis.han.de> for his help.