<HTML ><HEAD ><TITLE >Testing the network booting</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK REL="HOME" HREF="t1.html"><LINK REL="PREVIOUS" TITLE="Setting up a diskless boot" HREF="x126.html"><LINK REL="NEXT" TITLE="Booting DOS" HREF="x216.html"></HEAD ><BODY CLASS="sect1" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" ></TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="x126.html" ACCESSKEY="P" >Prev</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x216.html" ACCESSKEY="N" >Next</A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="sect1" ><H1 CLASS="sect1" ><A NAME="AEN186" ></A >Testing the network booting</H1 ><P > Now when you start up Etherboot, it should obtain an IP address and print out what it received. If you do not get this to work, turn on debugging in DHCPD and see if any query was received. You may also wish to use the tcpdump or ethereal utilities to watch the network for DHCP packets (port bootps). If not, check your network hardware (cables, etc). If a query was received, check if DHCPD was able to give an answer. If not, then the Ethernet address was not found in <TT CLASS="filename" >/etc/dhcpd.conf</TT >. If a reply was sent, then only faulty hardware or a bug in Etherboot would prevent it being received by Etherboot. </P ><P > Assuming an IP address was received, the next thing Etherboot tries to do is load a file using tftp. Check your system logs to see if a tftp daemon was started up and a file requested. Generally if you run tftpd under tcpwrapper security, a log entry will be generated. If not, it could be a path problem or file permission problem (the file needs to be readable by tftpd). Another problem could be that tftpd needs to reverse map the IP address to a name for security checking, and you don't have the client's details in <TT CLASS="filename" >/etc/hosts</TT > or in DNS, or your tcpwrapper config files (<TT CLASS="filename" >/etc/hosts.deny</TT >, <TT CLASS="filename" >/etc/hosts/allow</TT >) do not allow the access. Fix the problem. </P ><P > After the boot image is loaded, Etherboot will jump to it. If it crashes here, check that the image is a boot image. If it executes and stops at the point where it's trying to mount NFS filesystems, then you need to check your NFS mounts. Another common problem is the shared libraries on the NFS partition are not suitable for your CPU, e.g. i586 libraries but a 486 diskless client. </P ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="AEN195" ></A >Setting up an initrd filesystem</H2 ><P > Recent advances in the Linux kernel (2.4 and above) have made the use of an initrd that does user space autoconfiguration and mounting of a NFS root filesystem, followed by a pivot_root, a more flexible alternative to kernel autoconfiguration and mounting of a NFS root filesystem. Postings on the kernel mailing lists indicate that at some point in the future, kernel level autoconfiguration (BOOTP/DHCP from the kernel) may be removed from the Linux kernel and initrds will be the recommended way to start up a diskless system. </P ><P > Until I have time to write detailed instructions on how to construct the initrd, I refer you to the <A HREF="http://www.ltsp.org/" TARGET="_top" >LTSP distribution</A > which uses this technique. Mknbi supports initrds, see the ramdisk argument of <A HREF="../mknbi.html" TARGET="_top" >mkelf-linux</A >. The Linux kernel documentation describes the extra arguments should be passed to the kernel to make it use an initrd, and how to arrange the initrd so that the startup script within it is called when it's mounted. If the initrd mounts a NFS root filesystem then it should still have all the needed structure as explained in the next section. </P ><P > Initrds can also be used for mounting other network filesystems instead of NFS root. Some applications could even run totally out of initrd, e.g. <A HREF="http://www.zelow.no/floppyfw/" TARGET="_top" >Floppy Firewall</A >, provided you have the memory, of course. </P ></DIV ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="AEN203" ></A >Other filesystem setups</H2 ><P > This tutorial does not cover all possible ways of setting up a diskless client's initial filesystem. You could even mount a conventional hard disk. Why would you want to boot "diskless" if you have a hard disk? Reasons might be: you do not wish to administer the local disk; you want the assurance that a system is running a kernel from a central server; or you like the speed of network booting. Network booting is one technique in a toolbox. Techniques can be combined to do what you want. If you are interested in running the diskless client as an X-terminal, a very common use, you may wish to investigate the <A HREF="http://www.ltsp.org/" TARGET="_top" >Linux Terminal Server Project</A >. </P ></DIV ><DIV CLASS="sect2" ><H2 CLASS="sect2" ><A NAME="AEN207" ></A >Swap over NFS</H2 ><P > Swap over NFS can be arranged but you have to patch the kernel source. See <A HREF="http://nfs-swap.dot-heine.de" TARGET="_top" >here</A >. </P ><P > Be aware that opinions are divided on NFS swap. Some people think it's a bad thing because it just kills the network if you have lots of diskless computers and that you shouldn't be running into a swap regime on a diskless computer anyway. Some other people like having a bit of insurance. </P ><P > Also have a look at the <A HREF="http://atrey.karlin.mff.cuni.cz/~pavel/nbd/nbd.html" TARGET="_top" >NBD</A > Network Block Device for swapping over that. </P ><P > There is also the follow-on project <A HREF="http://www.it.uc3m.es/~ptb/nbd/" TARGET="_top" >ENBD</A >, the Enhanced Network Block Driver. I have no experience with this for swapping. 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