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-rw-r--r--Documentation/filesystems/nfs/nfsroot.txt70
1 files changed, 60 insertions, 10 deletions
diff --git a/Documentation/filesystems/nfs/nfsroot.txt b/Documentation/filesystems/nfs/nfsroot.txt
index 5efae00f6c7f..d2963123eb1c 100644
--- a/Documentation/filesystems/nfs/nfsroot.txt
+++ b/Documentation/filesystems/nfs/nfsroot.txt
@@ -5,6 +5,7 @@ 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>
@@ -79,7 +80,7 @@ nfsroot=[<server-ip>:]<root-dir>[,<nfs-options>]
ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
- <dns0-ip>:<dns1-ip>
+ <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
@@ -110,6 +111,9 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
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.
@@ -123,10 +127,13 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
Default: Determined using autoconfiguration.
- <hostname> Name of the client. May be supplied by autoconfiguration,
- but its absence will not trigger autoconfiguration.
- If specified and DHCP is used, the user provided hostname will
- be carried in the DHCP request to hopefully update DNS record.
+ <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.
@@ -162,12 +169,55 @@ ip=<client-ip>:<server-ip>:<gw-ip>:<netmask>:<hostname>:<device>:<autoconf>:
Default: any
- <dns0-ip> IP address of first nameserver.
- Value gets exported by /proc/net/pnp which is often linked
- on embedded systems by /etc/resolv.conf.
+ <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.
- <dns1-ip> IP address of second nameserver.
- Same as above.
+ 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