From 6ded55da6be9f186ae1022724a5881b43846c164 Mon Sep 17 00:00:00 2001 From: "J. Bruce Fields" Date: Mon, 7 Apr 2008 15:59:03 -0400 Subject: Documentation: move nfsroot.txt to filesystems/ Documentation/ is a little large, and filesystems/ seems an obvious place for this file. Signed-off-by: J. Bruce Fields Signed-off-by: Jonathan Corbet --- Documentation/nfsroot.txt | 270 ---------------------------------------------- 1 file changed, 270 deletions(-) delete mode 100644 Documentation/nfsroot.txt (limited to 'Documentation/nfsroot.txt') diff --git a/Documentation/nfsroot.txt b/Documentation/nfsroot.txt deleted file mode 100644 index 31b329172343..000000000000 --- a/Documentation/nfsroot.txt +++ /dev/null @@ -1,270 +0,0 @@ -Mounting the root filesystem via NFS (nfsroot) -=============================================== - -Written 1996 by Gero Kuhlmann -Updated 1997 by Martin Mares -Updated 2006 by Nico Schottelius -Updated 2006 by Horms - - - -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/initrd.txt) 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=[:][,] - - If the `nfsroot' parameter is NOT given on the command line, - the default "/tftpboot/%s" will be used. - - 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. - - 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. - - 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=:::::: - - 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 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". - - IP address of the client. - - Default: Determined using autoconfiguration. - - 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 for NFS root. That is autoconfiguration - will not be triggered if it is missing and NFS root is not - in operation. - - Default: Determined using autoconfiguration. - The address of the autoconfiguration server is used. - - IP address of a gateway if the server is on a different subnet. - - Default: Determined using autoconfiguration. - - Netmask for local network interface. If unspecified - the netmask is derived from the client IP address assuming - classful addressing. - - Default: Determined using autoconfiguration. - - Name of the client. May be supplied by autoconfiguration, - but its absence will not trigger autoconfiguration. - - Default: Client IP address is used in ASCII notation. - - 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. - - 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) - - Default: any - - - - -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 - 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//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/i386/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 - -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 ". 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/serial-console.txt 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 . - - The rest of the IP layer autoconfiguration code has been written - by Martin Mares . - - In order to write the initial version of nfsroot I would like to thank - Jens-Uwe Mager for his help. -- cgit v1.2.3