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| slackware:pxe [2006/10/01 20:41] – Another typo fixed (tnaks volkerdi!). alien | slackware:pxe [2006/10/02 19:57] – Some typos fixed. alien |
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| The commonly used method of booting a computer over the network is called [[wp>Preboot_Execution_Environment|PXE]] or **P**reboot E**x**ecution **E**nvironment. If you want your computer to boot using PXE, it needs a network card with PXE-capable firmware, and a BIOS that supports network boot. Most modern network cards (and computers) sold on the market today support this. When a computer boots from the network , it is the network card that downloads the bootloader, kernel and a filesystem - any Operating System that might already be installed on the computer will be untouched.\\ You can just as well boot a diskless computer using PXE - in fact this is how [[wp>Thin_client|Thin Clients]] and the [[http://ltsp.org/|Linux Terminal Server Project]] work. | The commonly used method of booting a computer over the network is called [[wp>Preboot_Execution_Environment|PXE]] or **P**reboot E**x**ecution **E**nvironment. If you want your computer to boot using PXE, it needs a network card with PXE-capable firmware, and a BIOS that supports network boot. Most modern network cards (and computers) sold on the market today support this. When a computer boots from the network , it is the network card that downloads the bootloader, kernel and a filesystem - any Operating System that might already be installed on the computer will be untouched.\\ You can just as well boot a diskless computer using PXE - in fact this is how [[wp>Thin_client|Thin Clients]] and the [[http://ltsp.org/|Linux Terminal Server Project]] work. |
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| Of course, the other end of the network needs our attention, too. A //PXE server// needs to be available on the local network. The PXE firmware in your computer's network card will contact this server in order to fetch some kind of bootable program code and bootstrap itself. What happens //after// the computer boots has no longer anything to do with the PXE boot stage, it is the bootstrapping process we're insterested in. | Of course, the other end of the network needs our attention, too. A //PXE server// needs to be available on the local network. The PXE firmware in your computer's network card will contact this server in order to fetch some kind of bootable program code and bootstrap itself. What happens //after// the computer boots has no longer anything to do with the PXE boot stage, it is the bootstrapping process we're interested in. |
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| We will cover the requirements for such a server in one of the [[#server_requirements|next paragraphs]]. | We will cover the requirements for such a server in one of the [[#server_requirements|next paragraphs]]. |
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| The Slackware network installation process will be roughly as follows: | The Slackware network installation process will roughly be as follows: |
| * You start the computer that is going to receive Slackware; | * You start the computer that is going to receive Slackware; |
| * On startup, you make sure you select //network boot// in the BIOS startup - either by activating a ''custom startup sequence'', by entering a ''boot menu'' by pressing a function key like <key>F12</key>, or else by preselecting ''network boot'' as first option in the BIOS. | * On startup, you make sure you select //network boot// in the BIOS startup - either by activating a ''custom startup sequence'', by entering a ''boot menu'' by pressing a function key like <key>F12</key>, or else by preselecting ''network boot'' as first option in the BIOS. |
| * When the computer boots, the network card activates it's PXE code and tries to contact a PXE server. When such a server exists on the LAN, it will tell the card where to download a piece of bootable code, an Operating System kernel (the Slackware Linux kernel) and an initial ramdisk (aka initrd - the compressed root-filesystem image where the setup program, libraries and kernel modules are stored). You will see a page full of mumbo-jumbo as the card broadcasts on the LAN, and probes for possible candidate configurations to download; | * When the computer boots, the network card activates its PXE code and tries to contact a PXE server. When such a server exists on the LAN, it will tell the card where to download a piece of bootable code, an Operating System kernel (the Slackware Linux kernel) and an initial ramdisk (aka initrd - the compressed root-filesystem image where the setup program, libraries and kernel modules are stored). You will see a page full of mumbo-jumbo as the card broadcasts on the LAN, and probes for possible candidate configurations to download; |
| * If a willing PXE server was found, your computer's network card will then download a kernel and initrd, boot the Linux kernel, unpack the initrd into a ramdisk and start the Slackware installer's initialization sequence. This is where you'll be in familiar territory again, since this is exactly what happens if you had booted from a CDROM or a floppy. But the fun is not over... | * If a willing PXE server was found, your computer's network card will then download a kernel and initrd, boot the Linux kernel, unpack the initrd into a ramdisk and start the Slackware installer's initialization sequence. This is where you'll be in familiar territory again, since this is exactly what happens if you had booted from a CDROM or a floppy. But the fun is not over... |
| * Since we booted the computer using code that did not originate from our computer, we will have to fetch the remainder of the data - the Slackware packages - from the network as well. It's just that the freshly booted Linux kernel has no idea how it came to be running on the computer: you will have to initialize the network all over again. The network card's PXE firmware has done it's job and is no longer in the picture. So: | * Since we booted the computer using code that did not originate from our computer, we will have to fetch the remainder of the data - the Slackware packages - from the network as well. It's just that the freshly booted Linux kernel has no idea how it came to be running on the computer: you will have to initialize the network all over again. The network card's PXE firmware has done it's job and is no longer in the picture. So: |
| * We need to load a kernel driver for our network card and locate a NFS server that holds the Slackware package tree. Currently, NFS is our only means of getting to network data at all. Before starting ''cfdisk'' and ''setup'', we need to run the (''pcmcia'' and/or) ''network'' command to probe the network card and load a suitable driver. If your network card is not supported by any of the available drivers, you're out of luck and will have to rethink your options. | * We need to load a kernel driver for our network card and locate a NFS server that holds the Slackware package tree. Currently, NFS is our only means of getting to network data at all. Before starting ''cfdisk'' and ''setup'', we need to run the (''pcmcia'' and/or) ''network'' command to probe the network card and load a suitable driver. If your network card is not supported by any of the available drivers, you're out of luck and will have to re-evaluate your options. |
| * From here on, installation proceeds as usual, under the condition that you select //NFS server// as the source of the Slackware packages. | * From here on, installation proceeds as usual, under the condition that you select //NFS server// as the source of the Slackware packages. |
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| This is the interesting part (well in my opinion at least - many people consider this as a dark art).\\ | This is the interesting part (well in my opinion at least - many people consider this as a dark art).\\ |
| A PXE Server is really a mix of several components. We need | A PXE Server is really a mix of several components. We need |
| * A service that understands the //BOOTP// protocol. BOOTP is a network protocol somewhat like DHCP, and it is used by the PXE firmware to broadcast on the network it's desire to find a suitable server to download the bootstrap code from. The DHCP Server that is part of Slackware fulfills this requirement, since it talks BOOTP as well as DHCP. | * A service that understands the //BOOTP// protocol. BOOTP is a network protocol somewhat like DHCP, and it is used by the PXE firmware to broadcast on the network its desire to find a suitable server to download the bootstrap code from. The ISC DHCP Server which comes as part of Slackware fulfills this requirement, since it supports BOOTP as well as DHCP. |
| * A download service for the bootstrap code. A //TFTP// (trivial file transfer protocol) server is needed for this. Slackware ships with an implementation of a TFTP server called tftpd-hpa which does what we need. | * A download service for the bootstrap code. A //TFTP// (trivial file transfer protocol) server is needed for this. Slackware ships with an implementation of a TFTP server called tftpd-hpa which does what we need. |
| * And for the Slackware installer, a NFS server is required because we must perform a network install. Slackware does not know the concept of installation from a ftp server (yet?). We can use Slackware's stock NFS server for that. | * And for the Slackware installer, a NFS server is required because we must perform a network install. Slackware does not know the concept of installation from a ftp server (yet?). We can use Slackware's stock NFS server for that. |
| You probably already have a DHCP server running on your network. You can try and modify it's configuration so that it will do want we want, or if that is impossible (for instance because the DHCP server is running on your DSL/Cable router) you could consider disabling that and setting up a Slackware DHCP server for your LAN with much enhanced functionality. | You probably already have a DHCP server running on your network. You can try and modify it's configuration so that it will do want we want, or if that is impossible (for instance because the DHCP server is running on your DSL/Cable router) you could consider disabling that and setting up a Slackware DHCP server for your LAN with much enhanced functionality. |
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| Slackware includes the //ISC DHCP// server package (dhcpd). Two example ''/etc/dhcpd.conf'' configuration files for this DHCP Server is included in the [[#example_configuration_scripts|last section]] of the article. | Slackware includes the //ISC DHCP// server package (dhcpd). Two example ''/etc/dhcpd.conf'' configuration files for this DHCP Server are included in the [[#example_configuration_scripts|last section]] of the article. |
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| If you don't want to be bothered with fancy configurations but want a quick solution that will just work for your network, use the [[#first_example_dhcpd.conf|first (simple) example]] ''/etc/dhcpd.conf'' configuration file as well as the provided ''/etc/rc.d/rc.dhcpd'' [[#rc_script|start script]] and you'll be up and running in minutes. It requires //no// editing of files, the examples will work out of the box. | If you don't want to be bothered with fancy configurations but want a quick solution that will just work for your network, use the [[#first_example_dhcpd.conf|first (simple) example]] ''/etc/dhcpd.conf'' configuration file as well as the provided ''/etc/rc.d/rc.dhcpd'' [[#rc_script|start script]] and you'll be up and running in minutes. It requires //no// editing of files, the examples will work out of the box. |
| mount -o loop,ro /mirror/Slackware/slackware-11.0/isolinux/network.dsk network/ | mount -o loop,ro /mirror/Slackware/slackware-11.0/isolinux/network.dsk network/ |
| </code> You've probably noticed I mount these images read-only; we're only going to copy files //out// of them. | </code> You've probably noticed I mount these images read-only; we're only going to copy files //out// of them. |
| * Use the ''dd'' command to create a new file of sufficient size (called ''newinitrd''). At the end of the process this file will contain a filesystem which holds the combined contents of the Slackware disk images we just loop-mounted.\\ With "sufficient" I mean the size must be at least the combined sizes of the uncompressed disk images we are going to copy into our new filesystem. In my example ''dd'' command below I use a count of ''9500'' 1kB sized blocks which amounts to a 9.5MB file: <code> | * Use the ''dd'' command to create a new file of sufficient size (called ''newinitrd''). At the end of the process this file will contain a filesystem which holds the combined contents of the Slackware disk images we just loop-mounted.\\ With "sufficient" I mean the size must be at least the combined sizes of the uncompressed disk images we are going to copy into our new filesystem. In my example ''dd'' command below I use a number of ''9500'' 1kB sized blocks which amounts to a 9.5MB file: <code> |
| dd if=/dev/zero of=/tmp/pxe/newinitrd bs=1k count=9500 | dd if=/dev/zero of=/tmp/pxe/newinitrd bs=1k count=9500 |
| </code> How did I get at that number ''9500''? Well, you sum the sizes of the ''initrd.dsk'', ''network.dsk'' and ''pcmcia.dsk'' files and make sure you use a number that is not lower than that sum. The following command is the geek way to return the sum value: <code>echo $(( $(du -sk initrd.dsk|cut -f1)+$(du -sk network.dsk|cut -f1)+$(du -sk pcmcia.dsk|cut -f1) )) | </code> How did I get at that number ''9500''? Well, you sum the sizes of the ''initrd.dsk'', ''network.dsk'' and ''pcmcia.dsk'' files and make sure you use a number that is not smaller than that sum. The following command is the geek way to return the sum value: <code>echo $(( $(du -sk initrd.dsk|cut -f1)+$(du -sk network.dsk|cut -f1)+$(du -sk pcmcia.dsk|cut -f1) )) |
| </code> | </code> |
| * We then create a filesystem //inside// this file (and use the ''-F'' flag to ''mkfs.ext2'' to indicate that we are fully aware we're applying the command to a non-block device). Also, tune the filesystem so that it will never ever ask for a filesystem check (''fsck'') when it gets mounted: <code> | * We then create a filesystem //inside// this file (and use the ''-F'' flag to ''mkfs.ext2'' to indicate that we are fully aware we're applying the command to a non-block device). Also, tune the filesystem so that it will never ever ask for a filesystem check (''fsck'') when it gets mounted: <code> |
| </code> | </code> |
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| <note tip> I have written a script //create_slackboots.sh// that does all of this fully automatically (and more!), and you can download it at [[http://www.slackware.com/~alien/tools/slackboot/|http://www.slackware.com/~alien/tools/slackboot/]]. Do not forget to also download the other files that you'll find at that URL, because the script needs those to patch the pcmcia and network scripts. Be aware that this script also adds the content of ''network26.dsk'' (the network drivers for the ''huge26.s'' kernel) to our big new ''initrd.img'', which is something I omitted the detailed steps above in order to keep it readable</note> | <note tip> I have written a script //create_slackboots.sh// that does all of this fully automatically (and more!), and you can download it at [[http://www.slackware.com/~alien/tools/slackboot/|http://www.slackware.com/~alien/tools/slackboot/]]. Do not forget to also download the other files that you'll find at that URL, because the script needs those to patch the pcmcia and network scripts. Be aware that this script also adds the content of ''network26.dsk'' (the network drivers for the ''huge26.s'' kernel) to our big new ''initrd.img'', which is something I omitted from the detailed steps above in order to keep the story readable</note> |
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| <note> You can also just download a [[http://www.slackware.com/~alien/slackboot/pxe/initrd.img|ready-made initrd.img]] of course. | <note> You can also just download a [[http://www.slackware.com/~alien/slackboot/pxe/initrd.img|ready-made initrd.img]] of course. |
| I have an accompanying [[http://www.slackware.com/~alien/slackboot/pxe/pxelinux.cfg/default|pxelinux configuration file]] too. If you rather create that file yourself, use the aforementioned //create_slackboots.sh// script or read the next paragraph.</note> | I have an accompanying [[http://www.slackware.com/~alien/slackboot/pxe/pxelinux.cfg/default|pxelinux configuration file]] too. If you rather want to create that file yourself, use the aforementioned //create_slackboots.sh// script or read the next paragraph.</note> |
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| ==== Creating a pxelinux configuration file ==== | ==== Creating a pxelinux configuration file ==== |
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| Save the isolinux.cfg file from the Slackware CDROM to the tftp directory: <code> | Copy the isolinux.cfg file from the Slackware CDROM to the tftp directory: <code> |
| mkdir -p /tftpboot/slackware-11.0/pxelinux.cfg | mkdir -p /tftpboot/slackware-11.0/pxelinux.cfg |
| cp /mirror/Slackware/slackware-11.0/isolinux/isolinux.cfg /tftpboot/slackware-11.0/pxelinux.cfg/default | cp /mirror/Slackware/slackware-11.0/isolinux/isolinux.cfg /tftpboot/slackware-11.0/pxelinux.cfg/default |
