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Documentation: nfsroot.txt: convert to ReST
Convert nfsroot.txt to RST and move it to admin-guide. Content remains mostly the same. Signed-off-by: Daniel W. S. Almeida <[email protected]> Link: https://lore.kernel.org/r/442d35917351f5260dd8ed7362e9b5f1264ef8ad.1578697871.git.dwlsalmeida@gmail.com Signed-off-by: Jonathan Corbet <[email protected]>
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@@ -6,3 +6,4 @@ NFS | |
| :maxdepth: 1 | ||
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| nfs-client | ||
| nfsroot | ||
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| @@ -1,27 +1,33 @@ | ||
| =============================================== | ||
| Mounting the root filesystem via NFS (nfsroot) | ||
| =============================================== | ||
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| Written 1996 by Gero Kuhlmann <[email protected]> | ||
| Updated 1997 by Martin Mares <[email protected]> | ||
| Updated 2006 by Nico Schottelius <[email protected]> | ||
| Updated 2006 by Horms <[email protected]> | ||
| Updated 2018 by Chris Novakovic <[email protected]> | ||
| :Authors: | ||
| Written 1996 by Gero Kuhlmann <[email protected]> | ||
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| Updated 1997 by Martin Mares <[email protected]> | ||
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| Updated 2006 by Nico Schottelius <[email protected]> | ||
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| Updated 2006 by Horms <[email protected]> | ||
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| Updated 2018 by Chris Novakovic <[email protected]> | ||
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| 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 | ||
| 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. | ||
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| 1.) Enabling nfsroot capabilities | ||
| ----------------------------- | ||
| Enabling nfsroot capabilities | ||
| ============================= | ||
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| In order to use nfsroot, NFS client support needs to be selected as | ||
| built-in during configuration. Once this has been selected, the nfsroot | ||
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@@ -34,8 +40,8 @@ DHCP, BOOTP and RARP is safe. | |
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| 2.) Kernel command line | ||
| ------------------- | ||
| Kernel command line | ||
| =================== | ||
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| 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 | ||
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@@ -44,19 +50,17 @@ This can be established using the following kernel command line parameters: | |
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| root=/dev/nfs | ||
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| 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. | ||
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| nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] | ||
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| If the `nfsroot' parameter is NOT given on the command line, | ||
| the default "/tftpboot/%s" will be used. | ||
| the default ``"/tftpboot/%s"`` will be used. | ||
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| <server-ip> Specifies the IP address of the NFS server. | ||
| The default address is determined by the `ip' parameter | ||
| The default address is determined by the ip parameter | ||
| (see below). This parameter allows the use of different | ||
| servers for IP autoconfiguration and NFS. | ||
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@@ -66,7 +70,8 @@ nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] | |
| IP address. | ||
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| <nfs-options> Standard NFS options. All options are separated by commas. | ||
| The following defaults are used: | ||
| The following defaults are used:: | ||
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| port = as given by server portmap daemon | ||
| rsize = 4096 | ||
| wsize = 4096 | ||
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@@ -79,31 +84,29 @@ nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>] | |
| flags = hard, nointr, noposix, cto, ac | ||
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| ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>: | ||
| <dns0-ip>:<dns1-ip>:<ntp0-ip> | ||
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| 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 | ||
| 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. | ||
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| 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. | ||
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| The <autoconf> parameter can appear alone as the value to the `ip' | ||
| 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". | ||
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| <client-ip> IP address of the client. | ||
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| Default: Determined using autoconfiguration. | ||
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| <server-ip> IP address of the NFS server. If RARP is used to determine | ||
| <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. | ||
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| (see below). | ||
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| Default: Determined using autoconfiguration. | ||
| The address of the autoconfiguration server is used. | ||
| The address of the autoconfiguration server is used. | ||
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| <gw-ip> IP address of a gateway if the server is on a different subnet. | ||
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| Default: Determined using autoconfiguration. | ||
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| <netmask> Netmask for local network interface. If unspecified | ||
| the netmask is derived from the client IP address assuming | ||
| classful addressing. | ||
| <netmask> Netmask for local network interface. | ||
| If unspecified the netmask is derived from the client IP address | ||
| assuming classful addressing. | ||
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| Default: Determined using autoconfiguration. | ||
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| <hostname> Name of the client. If a '.' character is present, anything | ||
| <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. | ||
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| Default: Client IP address is used in ASCII notation. | ||
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| <device> Name of network device to use. | ||
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| 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. | ||
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| <autoconf> Method to use for autoconfiguration. In the case of options | ||
| which specify multiple autoconfiguration protocols, | ||
| 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. | ||
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| <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. | ||
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| Only autoconfiguration protocols that have been compiled | ||
| into the kernel will be used, regardless of the value of | ||
| this option. | ||
| this option:: | ||
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| off or none: don't use autoconfiguration | ||
| (do static IP assignment instead) | ||
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| nfsrootdebug | ||
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| 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. | ||
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| rdinit=<executable file> | ||
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| 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. | ||
| kernel command line parameters, including 'nfsroot=', are ignored. | ||
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| A description of the process of mounting the root file system can be | ||
| found in: | ||
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| Documentation/driver-api/early-userspace/early_userspace_support.rst | ||
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| found in Documentation/driver-api/early-userspace/early_userspace_support.rst | ||
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| 3.) Boot Loader | ||
| ---------- | ||
| Boot Loader | ||
| =========== | ||
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| To get the kernel into memory different approaches can be used. | ||
| They depend on various facilities being available: | ||
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| 3.1) Booting from a floppy using syslinux | ||
| - Booting from a floppy using syslinux | ||
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| 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. | ||
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| e.g. | ||
| e.g:: | ||
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| make bzdisk FDARGS="root=/dev/nfs" | ||
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| Note that the user running this command will need to have | ||
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@@ -267,48 +265,56 @@ They depend on various facilities being available: | |
| For more information on syslinux, including how to create bootdisks | ||
| for prebuilt kernels, see http://syslinux.zytor.com/ | ||
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| 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. | ||
| .. note:: | ||
| 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. | ||
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| 3.2) Booting from a cdrom using isolinux | ||
| - Booting from a cdrom using isolinux | ||
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| 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. | ||
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| e.g. | ||
| e.g:: | ||
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| make isoimage FDARGS="root=/dev/nfs" | ||
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| 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. | ||
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| e.g. | ||
| e.g:: | ||
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| cdrecord dev=ATAPI:1,0,0 arch/x86/boot/image.iso | ||
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| For more information on isolinux, including how to create bootdisks | ||
| for prebuilt kernels, see http://syslinux.zytor.com/ | ||
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| 3.2) Using LILO | ||
| - Using LILO | ||
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| When using LILO all the necessary command line parameters may be | ||
| specified using the 'append=' directive in the LILO configuration | ||
| file. | ||
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| However, to use the 'root=' directive you also need to create | ||
| a dummy root device, which may be removed after LILO is run. | ||
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| mknod /dev/boot255 c 0 255 | ||
| e.g:: | ||
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| mknod /dev/boot255 c 0 255 | ||
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| For information on configuring LILO, please refer to its documentation. | ||
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| 3.3) Using GRUB | ||
| - Using GRUB | ||
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| When using GRUB, kernel parameter are simply appended after the kernel | ||
| specification: kernel <kernel> <parameters> | ||
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| 3.4) Using loadlin | ||
| - Using loadlin | ||
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| 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 | ||
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| Please refer to the loadlin documentation for further information. | ||
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| 3.5) Using a boot ROM | ||
| - Using a boot ROM | ||
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| 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 | ||
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@@ -326,7 +333,8 @@ They depend on various facilities being available: | |
| etherboot, both of which are available on sunsite.unc.edu, and both | ||
| of which contain everything you need to boot a diskless Linux client. | ||
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| 3.6) Using pxelinux | ||
| - Using pxelinux | ||
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| Pxelinux may be used to boot linux using the PXE boot loader | ||
| which is present on many modern network cards. | ||
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| 4.) Credits | ||
| ------- | ||
| Credits | ||
| ======= | ||
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| The nfsroot code in the kernel and the RARP support have been written | ||
| by Gero Kuhlmann <[email protected]>. | ||
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