Difference between revisions of "PXE"

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(Boot: journalctl instead of syslog.)
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[[Category:Networking]]
 
[[Category:Networking]]
 
[[Category:Boot process]]
 
[[Category:Boot process]]
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[[es:PXE]]
 
[[fr:Install PXE]]
 
[[fr:Install PXE]]
 
[[ru:Install Arch from network via PXE (Русский)]]
 
[[ru:Install Arch from network via PXE (Русский)]]
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{{bc|1=
 
{{bc|1=
 
# mkdir -p /mnt/archiso
 
# mkdir -p /mnt/archiso
# mount -o loop,ro archlinux-2013.02.01-dual.iso /mnt/archiso}}
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# mount -o loop,ro archlinux-2013.08.01-dual.iso /mnt/archiso}}
  
 
== Server setup ==
 
== Server setup ==
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== Alternate Methods ==
 
== Alternate Methods ==
 
{{Accuracy|verify}}
 
{{Expansion}}
 
  
 
As implied in the syslinux menu, there are several other alternatives:
 
As implied in the syslinux menu, there are several other alternatives:
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=== NFS ===
 
=== NFS ===
  
You will need to setup a [[NFS|NFS server]] with the root export at the root of your mounted installation media--that would be {{ic|/mnt/archiso}} if you followed the [[PXE#Preparation|earlier sections]] of this guide.
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You will need to set up an [[NFS|NFS server]] with an export at the root of your mounted installation media, which would be {{ic|/mnt/archiso}} if you followed the [[PXE#Preparation|earlier sections]] of this guide.  After setting up the server, add the following line to your {{ic|/etc/exports}} file:
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{{hc|/etc/exports|/mnt/archiso 192.168.0.0/24(ro,no_subtree_check)}}
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If the server was already running, re-export the filesystems with {{ic|exportfs -r -a -v}}.
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The default settings in the installer expect to find the NFS at {{ic|/run/archiso/bootmnt}}, so you will need to edit the boot options.  To do this, press Tab on the appropriate boot menu choice and edit the {{ic|archiso_nfs_srv}} option accordingly:
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{{bc|1=archiso_nfs_srv=${pxeserver}:/mnt/archiso}}
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Alternatively, you can use {{ic|/run/archiso/bootmnt}} for the entire process.
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After the kernel loads, the Arch bootstrap image will copy the root filesystem via NFS to the booting host.  This can take a little while.  Once this completes, you should have a running system.
  
 
=== NBD ===
 
=== NBD ===
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{{Accuracy|verify}}
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{{Expansion}}
  
 
Install {{pkg|nbd}} and configure it:
 
Install {{pkg|nbd}} and configure it:
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[archiso]
 
[archiso]
 
     readonly = true
 
     readonly = true
     exportname = /dev/disk/by-label/ARCH_201208}}
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     exportname = /srv/archlinux-2013.02.01-dual.iso}}
  
 
=== Low memory ===
 
=== Low memory ===

Revision as of 19:41, 10 September 2013

Template:Article summary start Template:Article summary text Template:Article summary heading Template:Article summary wiki Template:Article summary end From Wikipedia:Preboot Execution Environment:

The Preboot eXecution Environment (PXE, also known as Pre-Execution Environment; sometimes pronounced "pixie") is an environment to boot computers using a network interface independently of data storage devices (like hard disks) or installed operating systems.

In this guide, PXE is used to boot the installation media with an appropriate option-rom that supports PXE on the target.

Preparation

Download the latest official install media from here.

Next mount the image:

# mkdir -p /mnt/archiso
# mount -o loop,ro archlinux-2013.08.01-dual.iso /mnt/archiso

Server setup

You'll need to setup a DHCP, TFTP, and HTTP server to configure networking, load pxelinux/kernel/initramfs, and finally load the root filesystem (respectively).

Network

Bring up your wired NIC, and assign it an address appropriately.

# ip link set eth0 up
# ip addr add 192.168.0.1/24 dev eth0

DHCP + TFTP

You'll need both a DHCP and TFTP server to configure networking on the install target and to facilitate the transfer of files between the PXE server and client; dnsmasq does both, and is extremely easy to set up.

Install dnsmasq:

# pacman -S dnsmasq

Configure dnsmasq:

# vim /etc/dnsmasq.conf
port=0
interface=eth0
bind-interfaces
dhcp-range=192.168.0.50,192.168.0.150,12h
dhcp-boot=/arch/boot/syslinux/pxelinux.0
dhcp-option-force=209,boot/syslinux/archiso.cfg
dhcp-option-force=210,/arch/
enable-tftp
tftp-root=/mnt/archiso

Start dnsmasq:

# systemctl start dnsmasq.service

HTTP

Thanks to recent changes in archiso, it is now possible to boot from HTTP (archiso_pxe_http initcpio hook) or NFS (archiso_pxe_nfs initcpio hook); among all alternatives, darkhttpd is by far the most trivial to setup (and the lightest-weight).

First, install darkhttpd:

# pacman -S darkhttpd

Then start darkhttpd using our /mnt/archiso as the document root:

# darkhttpd /mnt/archiso
darkhttpd/1.8, copyright (c) 2003-2011 Emil Mikulic.
listening on: http://0.0.0.0:80/

Installation

For this portion you'll need to figure out how to tell the client to attempt a PXE boot; in the corner of the screen along with the normal post messages, usually there will be some hint on which key to press to try PXE booting first. On an IBM x3650 F12 brings up a boot menu, the first option of which is Network; on a Dell PE 1950/2950 pressing F12 initiates PXE booting directly.

Boot

Looking at journald on the PXE server will provide some additional insight to what exactly is going on during the early stages of the PXE boot process:

# journalctl -u dnsmasq -f
dnsmasq-dhcp[2544]: DHCPDISCOVER(eth1) 00:1a:64:6a:a2:4d 
dnsmasq-dhcp[2544]: DHCPOFFER(eth1) 192.168.0.110 00:1a:64:6a:a2:4d 
dnsmasq-dhcp[2544]: DHCPREQUEST(eth1) 192.168.0.110 00:1a:64:6a:a2:4d 
dnsmasq-dhcp[2544]: DHCPACK(eth1) 192.168.0.110 00:1a:64:6a:a2:4d 
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/pxelinux.0 to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/whichsys.c32 to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso_pxe_choose.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/ifcpu64.c32 to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso_pxe_both_inc.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso_head.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso_pxe32.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso_pxe64.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/archiso_tail.cfg to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/vesamenu.c32 to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/syslinux/splash.png to 192.168.0.110

After you load pxelinux.0 and archiso.cfg via TFTP, you'll (hopefully) be presented with a syslinux boot menu with several options, two of which are of potential usefulness to us.

Select either

Boot Arch Linux (x86_64) (HTTP)

or

Boot Arch Linux (i686) (HTTP)

depending on your CPU architecture.

Next the kernel and initramfs (appropriate for the architecture you selected) will be transferred, again via TFTP:

dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/x86_64/vmlinuz to 192.168.0.110
dnsmasq-tftp[2544]: sent /mnt/archiso/arch/boot/x86_64/archiso.img to 192.168.0.110

If all goes well, you should then see activity on darkhttpd coming from the PXE-target; at this point the kernel would be loaded on the PXE-target, and in init:

1348347586 192.168.0.110 "GET /arch/aitab" 200 678 "" "curl/7.27.0"
1348347587 192.168.0.110 "GET /arch/x86_64/root-image.fs.sfs" 200 107860206 "" "curl/7.27.0"
1348347588 192.168.0.110 "GET /arch/x86_64/usr-lib-modules.fs.sfs" 200 36819181 "" "curl/7.27.0"
1348347588 192.168.0.110 "GET /arch/any/usr-share.fs.sfs" 200 63693037 "" "curl/7.27.0"

After the root filesystem is downloaded via HTTP, you'll eventually end up at a root zsh prompt with that fancy grml config.

Post-boot

Unless you want all traffic to be routed through your PXE server (which won't work anyway unless you set it up properly), you'll want to kill dnsmasq and get a new lease on the install target, as appropriate for your network layout.

# systemctl stop dnsmasq.service

You can also kill darkhttpd; the target has already downloaded the root filesystem, so it's no longer needed. While you're at it, you can also unmount the installation image:

# umount /mnt/archiso

At this point you can follow the official installation guide.

Alternate Methods

As implied in the syslinux menu, there are several other alternatives:

NFS

You will need to set up an NFS server with an export at the root of your mounted installation media, which would be /mnt/archiso if you followed the earlier sections of this guide. After setting up the server, add the following line to your /etc/exports file:

/etc/exports
/mnt/archiso 192.168.0.0/24(ro,no_subtree_check)

If the server was already running, re-export the filesystems with exportfs -r -a -v.

The default settings in the installer expect to find the NFS at /run/archiso/bootmnt, so you will need to edit the boot options. To do this, press Tab on the appropriate boot menu choice and edit the archiso_nfs_srv option accordingly:

archiso_nfs_srv=${pxeserver}:/mnt/archiso

Alternatively, you can use /run/archiso/bootmnt for the entire process.

After the kernel loads, the Arch bootstrap image will copy the root filesystem via NFS to the booting host. This can take a little while. Once this completes, you should have a running system.

NBD

Tango-inaccurate.pngThe factual accuracy of this article or section is disputed.Tango-inaccurate.png

Reason: verify (Discuss in Talk:PXE#)

Tango-view-fullscreen.pngThis article or section needs expansion.Tango-view-fullscreen.png

Reason: please use the first argument of the template to provide a brief explanation. (Discuss in Talk:PXE#)

Install nbd and configure it:

# vim /etc/nbd-server/config
[generic]
[archiso]
    readonly = true
    exportname = /srv/archlinux-2013.02.01-dual.iso

Low memory

The copytoram initramfs option can be used to control whether the root filesystem should be copied to ram in its entirety in early-boot.

It highly recommended to leave this option alone, and should only be disabled if entirely necessary (systems with less than ~256MB physical memory). Append copytoram=n to your kernel line if you wish to do so.