diff options
author | J. Bruce Fields <bfields@citi.umich.edu> | 2009-10-27 14:41:35 -0400 |
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committer | J. Bruce Fields <bfields@citi.umich.edu> | 2009-10-27 19:34:04 -0400 |
commit | dc7a08166f3a5f23e79e839a8a88849bd3397c32 (patch) | |
tree | 2feb8aed7b6142467e6b8833fbfd9838bda69c39 /Documentation/filesystems/nfsroot.txt | |
parent | e343eb0d60f74547e0aeb5bd151105c2e6cfe588 (diff) |
nfs: new subdir Documentation/filesystems/nfs
We're adding enough nfs documentation that it may as well have its own
subdirectory.
Acked-by: Randy Dunlap <rdunlap@xenotime.net>
Signed-off-by: J. Bruce Fields <bfields@citi.umich.edu>
Diffstat (limited to 'Documentation/filesystems/nfsroot.txt')
-rw-r--r-- | Documentation/filesystems/nfsroot.txt | 270 |
1 files changed, 0 insertions, 270 deletions
diff --git a/Documentation/filesystems/nfsroot.txt b/Documentation/filesystems/nfsroot.txt deleted file mode 100644 index 3ba0b945aaf8..000000000000 --- a/Documentation/filesystems/nfsroot.txt +++ /dev/null | |||
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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> | ||
6 | Updated 2006 by Nico Schottelius <nico-kernel-nfsroot@schottelius.org> | ||
7 | Updated 2006 by Horms <horms@verge.net.au> | ||
8 | |||
9 | |||
10 | |||
11 | In order to use a diskless system, such as an X-terminal or printer server | ||
12 | for example, it is necessary for the root filesystem to be present on a | ||
13 | non-disk device. This may be an initramfs (see Documentation/filesystems/ | ||
14 | ramfs-rootfs-initramfs.txt), a ramdisk (see Documentation/initrd.txt) or a | ||
15 | filesystem mounted via NFS. The following text describes on how to use NFS | ||
16 | for the root filesystem. For the rest of this text 'client' means the | ||
17 | diskless system, and 'server' means the NFS server. | ||
18 | |||
19 | |||
20 | |||
21 | |||
22 | 1.) Enabling nfsroot capabilities | ||
23 | ----------------------------- | ||
24 | |||
25 | In order to use nfsroot, NFS client support needs to be selected as | ||
26 | built-in during configuration. Once this has been selected, the nfsroot | ||
27 | option will become available, which should also be selected. | ||
28 | |||
29 | In the networking options, kernel level autoconfiguration can be selected, | ||
30 | along with the types of autoconfiguration to support. Selecting all of | ||
31 | DHCP, BOOTP and RARP is safe. | ||
32 | |||
33 | |||
34 | |||
35 | |||
36 | 2.) Kernel command line | ||
37 | ------------------- | ||
38 | |||
39 | When the kernel has been loaded by a boot loader (see below) it needs to be | ||
40 | told what root fs device to use. And in the case of nfsroot, where to find | ||
41 | both the server and the name of the directory on the server to mount as root. | ||
42 | This can be established using the following kernel command line parameters: | ||
43 | |||
44 | |||
45 | root=/dev/nfs | ||
46 | |||
47 | This is necessary to enable the pseudo-NFS-device. Note that it's not a | ||
48 | real device but just a synonym to tell the kernel to use NFS instead of | ||
49 | a real device. | ||
50 | |||
51 | |||
52 | nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] | ||
53 | |||
54 | If the `nfsroot' parameter is NOT given on the command line, | ||
55 | the default "/tftpboot/%s" will be used. | ||
56 | |||
57 | <server-ip> Specifies the IP address of the NFS server. | ||
58 | The default address is determined by the `ip' parameter | ||
59 | (see below). This parameter allows the use of different | ||
60 | servers for IP autoconfiguration and NFS. | ||
61 | |||
62 | <root-dir> Name of the directory on the server to mount as root. | ||
63 | If there is a "%s" token in the string, it will be | ||
64 | replaced by the ASCII-representation of the client's | ||
65 | IP address. | ||
66 | |||
67 | <nfs-options> Standard NFS options. All options are separated by commas. | ||
68 | The following defaults are used: | ||
69 | port = as given by server portmap daemon | ||
70 | rsize = 4096 | ||
71 | wsize = 4096 | ||
72 | timeo = 7 | ||
73 | retrans = 3 | ||
74 | acregmin = 3 | ||
75 | acregmax = 60 | ||
76 | acdirmin = 30 | ||
77 | acdirmax = 60 | ||
78 | flags = hard, nointr, noposix, cto, ac | ||
79 | |||
80 | |||
81 | ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf> | ||
82 | |||
83 | This parameter tells the kernel how to configure IP addresses of devices | ||
84 | and also how to set up the IP routing table. It was originally called | ||
85 | `nfsaddrs', but now the boot-time IP configuration works independently of | ||
86 | NFS, so it was renamed to `ip' and the old name remained as an alias for | ||
87 | compatibility reasons. | ||
88 | |||
89 | If this parameter is missing from the kernel command line, all fields are | ||
90 | assumed to be empty, and the defaults mentioned below apply. In general | ||
91 | this means that the kernel tries to configure everything using | ||
92 | autoconfiguration. | ||
93 | |||
94 | The <autoconf> parameter can appear alone as the value to the `ip' | ||
95 | parameter (without all the ':' characters before). If the value is | ||
96 | "ip=off" or "ip=none", no autoconfiguration will take place, otherwise | ||
97 | autoconfiguration will take place. The most common way to use this | ||
98 | is "ip=dhcp". | ||
99 | |||
100 | <client-ip> IP address of the client. | ||
101 | |||
102 | Default: Determined using autoconfiguration. | ||
103 | |||
104 | <server-ip> IP address of the NFS server. If RARP is used to determine | ||
105 | the client address and this parameter is NOT empty only | ||
106 | replies from the specified server are accepted. | ||
107 | |||
108 | Only required for NFS root. That is autoconfiguration | ||
109 | will not be triggered if it is missing and NFS root is not | ||
110 | in operation. | ||
111 | |||
112 | Default: Determined using autoconfiguration. | ||
113 | The address of the autoconfiguration server is used. | ||
114 | |||
115 | <gw-ip> IP address of a gateway if the server is on a different subnet. | ||
116 | |||
117 | Default: Determined using autoconfiguration. | ||
118 | |||
119 | <netmask> Netmask for local network interface. If unspecified | ||
120 | the netmask is derived from the client IP address assuming | ||
121 | classful addressing. | ||
122 | |||
123 | Default: Determined using autoconfiguration. | ||
124 | |||
125 | <hostname> Name of the client. May be supplied by autoconfiguration, | ||
126 | but its absence will not trigger autoconfiguration. | ||
127 | |||
128 | Default: Client IP address is used in ASCII notation. | ||
129 | |||
130 | <device> Name of network device to use. | ||
131 | |||
132 | Default: If the host only has one device, it is used. | ||
133 | Otherwise the device is determined using | ||
134 | autoconfiguration. This is done by sending | ||
135 | autoconfiguration requests out of all devices, | ||
136 | and using the device that received the first reply. | ||
137 | |||
138 | <autoconf> Method to use for autoconfiguration. In the case of options | ||
139 | which specify multiple autoconfiguration protocols, | ||
140 | requests are sent using all protocols, and the first one | ||
141 | to reply is used. | ||
142 | |||
143 | Only autoconfiguration protocols that have been compiled | ||
144 | into the kernel will be used, regardless of the value of | ||
145 | this option. | ||
146 | |||
147 | off or none: don't use autoconfiguration | ||
148 | (do static IP assignment instead) | ||
149 | on or any: use any protocol available in the kernel | ||
150 | (default) | ||
151 | dhcp: use DHCP | ||
152 | bootp: use BOOTP | ||
153 | rarp: use RARP | ||
154 | both: use both BOOTP and RARP but not DHCP | ||
155 | (old option kept for backwards compatibility) | ||
156 | |||
157 | Default: any | ||
158 | |||
159 | |||
160 | |||
161 | |||
162 | 3.) Boot Loader | ||
163 | ---------- | ||
164 | |||
165 | To get the kernel into memory different approaches can be used. | ||
166 | They depend on various facilities being available: | ||
167 | |||
168 | |||
169 | 3.1) Booting from a floppy using syslinux | ||
170 | |||
171 | When building kernels, an easy way to create a boot floppy that uses | ||
172 | syslinux is to use the zdisk or bzdisk make targets which use zimage | ||
173 | and bzimage images respectively. Both targets accept the | ||
174 | FDARGS parameter which can be used to set the kernel command line. | ||
175 | |||
176 | e.g. | ||
177 | make bzdisk FDARGS="root=/dev/nfs" | ||
178 | |||
179 | Note that the user running this command will need to have | ||
180 | access to the floppy drive device, /dev/fd0 | ||
181 | |||
182 | For more information on syslinux, including how to create bootdisks | ||
183 | for prebuilt kernels, see http://syslinux.zytor.com/ | ||
184 | |||
185 | N.B: Previously it was possible to write a kernel directly to | ||
186 | a floppy using dd, configure the boot device using rdev, and | ||
187 | boot using the resulting floppy. Linux no longer supports this | ||
188 | method of booting. | ||
189 | |||
190 | 3.2) Booting from a cdrom using isolinux | ||
191 | |||
192 | When building kernels, an easy way to create a bootable cdrom that | ||
193 | uses isolinux is to use the isoimage target which uses a bzimage | ||
194 | image. Like zdisk and bzdisk, this target accepts the FDARGS | ||
195 | parameter which can be used to set the kernel command line. | ||
196 | |||
197 | e.g. | ||
198 | make isoimage FDARGS="root=/dev/nfs" | ||
199 | |||
200 | The resulting iso image will be arch/<ARCH>/boot/image.iso | ||
201 | This can be written to a cdrom using a variety of tools including | ||
202 | cdrecord. | ||
203 | |||
204 | e.g. | ||
205 | cdrecord dev=ATAPI:1,0,0 arch/i386/boot/image.iso | ||
206 | |||
207 | For more information on isolinux, including how to create bootdisks | ||
208 | for prebuilt kernels, see http://syslinux.zytor.com/ | ||
209 | |||
210 | 3.2) Using LILO | ||
211 | When using LILO all the necessary command line parameters may be | ||
212 | specified using the 'append=' directive in the LILO configuration | ||
213 | file. | ||
214 | |||
215 | However, to use the 'root=' directive you also need to create | ||
216 | a dummy root device, which may be removed after LILO is run. | ||
217 | |||
218 | mknod /dev/boot255 c 0 255 | ||
219 | |||
220 | For information on configuring LILO, please refer to its documentation. | ||
221 | |||
222 | 3.3) Using GRUB | ||
223 | When using GRUB, kernel parameter are simply appended after the kernel | ||
224 | specification: kernel <kernel> <parameters> | ||
225 | |||
226 | 3.4) Using loadlin | ||
227 | loadlin may be used to boot Linux from a DOS command prompt without | ||
228 | requiring a local hard disk to mount as root. This has not been | ||
229 | thoroughly tested by the authors of this document, but in general | ||
230 | it should be possible configure the kernel command line similarly | ||
231 | to the configuration of LILO. | ||
232 | |||
233 | Please refer to the loadlin documentation for further information. | ||
234 | |||
235 | 3.5) Using a boot ROM | ||
236 | This is probably the most elegant way of booting a diskless client. | ||
237 | With a boot ROM the kernel is loaded using the TFTP protocol. The | ||
238 | authors of this document are not aware of any no commercial boot | ||
239 | ROMs that support booting Linux over the network. However, there | ||
240 | are two free implementations of a boot ROM, netboot-nfs and | ||
241 | etherboot, both of which are available on sunsite.unc.edu, and both | ||
242 | of which contain everything you need to boot a diskless Linux client. | ||
243 | |||
244 | 3.6) Using pxelinux | ||
245 | Pxelinux may be used to boot linux using the PXE boot loader | ||
246 | which is present on many modern network cards. | ||
247 | |||
248 | When using pxelinux, the kernel image is specified using | ||
249 | "kernel <relative-path-below /tftpboot>". The nfsroot parameters | ||
250 | are passed to the kernel by adding them to the "append" line. | ||
251 | It is common to use serial console in conjunction with pxeliunx, | ||
252 | see Documentation/serial-console.txt for more information. | ||
253 | |||
254 | For more information on isolinux, including how to create bootdisks | ||
255 | for prebuilt kernels, see http://syslinux.zytor.com/ | ||
256 | |||
257 | |||
258 | |||
259 | |||
260 | 4.) Credits | ||
261 | ------- | ||
262 | |||
263 | The nfsroot code in the kernel and the RARP support have been written | ||
264 | by Gero Kuhlmann <gero@gkminix.han.de>. | ||
265 | |||
266 | The rest of the IP layer autoconfiguration code has been written | ||
267 | by Martin Mares <mj@atrey.karlin.mff.cuni.cz>. | ||
268 | |||
269 | In order to write the initial version of nfsroot I would like to thank | ||
270 | Jens-Uwe Mager <jum@anubis.han.de> for his help. | ||