Building

The building again involves builder.rb. This time more parameters are needed:

    ruby builder.rb -u -n -s 1,2,bootconf \
        -p config/pkglist_neutral_rescue.txt \
        -c config/general_neutral_rescue.xml \
        -b config/branding_neutral_rescue.xml \
        -k config/kernels_rescue_unstable.xml > ../../llbuild/stage03.log 2>&1

The parameters are as follows:

• -u: build unstable, must match stage02
• -s: skip stages 1 and 2 and skip the generation of boot configuration files
• -p: use this package list
• -c: use this configuration file (specifies paths like the overlay)
• -b: use this branding
• -k: use the kernels noted here

You might also use --full to build an ISO containing all files from the chroot environment – this is self containing and can be used for building. Or use --skip-files to specify a filename containing a list of files to omit. After 30 to 40 minutes you’ll find the new ISO in /mnt/archiv/LessLinux/llbuild/stage03.

My next post will tell how to customize kernels and branding.

• LessLinux now supports tracking of dependencies after building packages. This allows to define the order of packages to build.

• As a consequence of the dependency tracking it is now also possible to parallelize the build. On a three core Athlon this brought down build times from around three days to less than 20 hours. With a faster machine you should even get better results.

Prerequesites

I assume that you already built stage01 on the same machine. If not, just create the directories as we did in the last article and mount the hard disk or partition containing sources and the stage01 chroot. The unprivileged user is not required this time.

Building

I prefer redirecting the console messages to a log file (and “tailing” it in another terminal). The build and install of the respective pacakges are separately logged to an package specific log file. I will later show how to analyze and them. So change to the build directory and run:

        ruby -I. builder.rb -s 1,3 -n -u -l -t 7 > /tmp/stage02.log 2>&1

This command uses six threads maximum. It really depends on your machine how many is ideal. As a rule of thumb, take twice the number of processor cores plus one. Less than three do not make sense, and above ten too many seeks may appear. Anyway: If you have a pretty fast box with a six core processor and you are maybe building on a SSD: try 15 or 20 threads and tell me how it compares to just ten.

Trouble

You will occasionally run into a problem where no modified files were found. In this case the builder exits. To find out which package is affected just grep for “no modified” in the log file:

        grep -A2 -i 'no modified' /tmp/stage02.log

This is most likely due to some race condition: The build or install script is not yet closed, but the builder already tries to run it. Take a look at the files /mnt/archiv/LessLinux/llbuild/stage02/build/packagename-version.build.log and packagename-version.install.log. If it reads bad interpreter … text file busy this is the problem. Sometimes the maximum number of open files is the problem, so you should compare the current number of open files with the maximum number during the threaded build.

To re-build the affected package delete the package and the file /tmp/LessLinux_Emergency_Exit and run the builder again:

        rm -rf /mnt/archiv/LessLinux/llbuild/stage02/build/packagename-version* /tmp/LessLinux_Emergency_Exit
        ruby -I. builder.rb -s 1,3 -n -u -l -t 7 >> /tmp/stage02.log 2>&1

When restarting the build all packages already built are ignored and the builder picks up where it left.

The next post will show how to assemble a working live system from the freshly created stage02.

• We switched from MySQL to SQLite3 as database during build

• LessLinux is self containing now, this means you can use LessLinux to build LessLinux to build LessLinux…

The stage01 build of LessLinux very closely resembles the chapter Chapter 5 – Constructing a Temporary System from Linux from Scratch. You’ll even notice similar environment variables. There will always be slight differences in package versions – this is intended. So you might be able to build LessLinux on any machine equipped with the right programs to build Linux from Scratch. But in my opinion do one of the two following things:

• Setup a clean Ubuntu 10.04 LTS and install all necessary packages by running
  apt-get install ` wget -O - http://download.lesslinux.org/builder/packagelists/20110202_ubuntu_1004_packages.txt `

• Download the latest FULL ISO, a build of LessLinux containing compilers, headers and stuff. FULL ISO images are currently around 1.5GB and they allow you to build LessLinux without having to permanently setup a build environment. As of this post being written the current FULL ISO is lesslinux-search-and-rescue-uluru-20110202-155012-FULL-en.iso

I strongly recommend to take a dedicated build box – with the FULL ISO and an USB hard drive the conversion will be temporary. This can be some fairly recent PC (2GHz, 1GB RAM) and a USB hard drive (30GB upwards – a 32GB thumb drive might also do the job). In the mid term we will concentrate on the self containing builds, so it’s best to get used to building with FULL ISO. The FULL ISO might also be a good starting point for anyone diving into Linux from Scratch since the versions of GCC and Glibc are usually close to those in LFS.

Directories and users

You have great freedom on directory layout and the unprivileged user that is used for building some packages, but for start you should stick with the defaults in LessLinux.

• I use /mnt/archiv/LessLinux as base for building. This path is used in the default config, so I suggest to keep it by mounting a dedicated build partition to /mnt/archiv/LessLinux:

  mkdir -p /mnt/archiv/LessLinux
  mkfs.ext3 /dev/sdx1
  mount /dev/sdx1 /mnt/archiv/LessLinux
  mkdir /mnt/archiv/LessLinux/llbuild
  mkdir /mnt/archiv/LessLinux/llbuilder
  mkdir /mnt/archiv/LessLinux/src

• Add an unprivileged user for building. He must have /bin/bash as a shell, otherwise the build will fail. The default scripts use mattias as unprivileged user:

  adduser -s /bin/bash mattias

Downloading and Building

You’ll need some buildscripts from http://download.lesslinux.org/src/. Take either the most recent ones or some that match a certain version you want to build. As I write this, lesslinux-search-and-rescue-uluru-20110202-155012-buildscripts.tbz is recommended.

• Go to the directory /mnt/archiv/LessLinux/llbuilder where you unpack the tarball:

  tar xvjf *-buildscripts.tbz

• Edit the file lesslinux-builder/config/general.xml and change the node unpriv to contain the username of the unprivileged user created above

• Change to the newly created directory lesslinux-builder, from there run:

  ruby -I. builder.rb -s 2,3 -n -u

This tells the builder to do an unstable (-u) build (glibc 2.12 and kernel 2.6.37 instead of glibc 2.11 and kernel 2.6.36). In a view days, I’ll move it to stable and take 2.6.38-rc and glibc 2.13 as unstable. The -n tells to omit tests. When making changes to stage01, you would probably omit this to run tests to discover problems. Finally -s makes the builder skipping stages 2 and 3.

Cleaning up

The build will now take somewhere between two and eight hours, strongly depending on how fast your machine is. After the build, the freshly created chroot environment and the database file containing will be backed up so that you can start any stage02 build without having to re-build stage01. Thus you should delete the build directory for stage01:

rm -rf /mnt/archiv/LessLinux/llbuild/stage01/build

And the next step…

Tomorrow I’ll describe how to build stage02 – which means building all packages in a chroot environment – and finally assembling an ISO image from it.

What’s new?

• Linux kernel 2.6.36.2
• The bootloader automatically detects if a PAE kernel has to be booted or not
• Xorg 7.6 with Xserver 1.9.3 and KMS enabled for Intel and AMD/Ati chipsets
• XFCE 4.6.2 as desktop environment
• Namoroka (Firefox) 3.6.13
• Minefield (Firefox) 4.0b8 (start with the command firefox40)
• Lanikai (Thunderbird) 3.1.7 with Enigmail and Lightning
• Abiword 2.8.6
• Gnumeric Spreadsheet 1.10.12
• Grsync 1.1.1
• Gparted 0.7.0
• KeePassX 0.4.3
• Xfburn 0.4.3
• Brasero 2.32.1
• Partition Image 0.6.9
• TrueCrypt 7.0a
• TestDisk/PhotoRec 6.12-WIP
• BusyBox 1.18.1

Download and Install

To download, select one of the ISO-Images linked below: LessLinux Search and Rescue 1.5 is currently available in German and English:

• lesslinux-search-and-rescue-uluru-20110110-081814-en.iso (English)
• lesslinux-search-and-rescue-uluru-20110110-081814-de.iso (German)

Please compare the SHA1SUMs after downloading:

        188210364ac91a13ec3b62f45e1787b3044878ed  lesslinux-search-and-rescue-uluru-20110110-081814-de.iso
        329db06d9340a3f25235ffa7f0d0e5b6b5d701d8  lesslinux-search-and-rescue-uluru-20110110-081814-en.iso

You might burn the ISO to a blank CD or DVD. Since the ISO images are prepared with “isohybrid” you can also directly copy them to a USB thumb drive. On Linux use the command:

        dd if=lesslinux-search-and-rescue-uluru-20110110-081814-??.iso of=/dev/sdx

On Windows, download Win32ImageWriter, rename the .iso to .img, format the thumb drive and use Win32ImageWriter to copy the image to the drive.

You might also install to an USB thumb drive of at least 2GB size by booting from CD/DVD. In this case the thumb drive will be partitioned into two volumes: The first volume will be FAT32 and accessible from Windows, the second partition will be EXT2 and only accessible from linux. During installation you can decide whether to create an encrypted container that will continue your home directory. This is useful to store shell scripts, book marks, logins for web pages etc.

VNC access

There are three boot options that start a VNC server instead of a local X-Server.

• Unsafe local VNC access Allow anyone to connect on port 5900 without a password. Since everyone has root rights, you should use this option only in trustworthy environments.
• Safe local VNC access A VNC server is started on localhost:5900 only, but SSH access with root privileges is granted (week password “test”). So you can tunnel port 5900 to you local machine. Please consider changing the rootpwhash to some safe password. The command openssl passwd -1 creates a hash. (Note: not working due to a bug in the boot config, press tab, search skipservices=|...| and there replace roothash with runtimeconf)
• Reverse VNC VNC is used to export the desktop via an outgoing connection instead of allowing incoming connections, you might want to use this feature in cases where it is impossible to accept incoming connections (some DSL providers, NAT behind NAT when connected via a 3.5G router).

Kexec

Another new feature is the Cheatcode kexec=http://server/path/kexec.conf. If the cheatcode is present, said config file will be downloaded and the kernel and initrd mentioned will be booted. Just take a look at this config to see how it works. Just one kernel is allowed, multiple initrds (one per line) will be concatenated. Make sure that append is on the last line. Currently the boot menu contains eight kexec entries to kickstart internet installation of current versions of openSUSE, Debian and Ubuntu (LTS and current stable) – all 32 and 64 bit. Eventually an entry to boot the latest bleeding edge version of LessLinux Search and Rescue will follow.

The blob directory

You might notice the directory /lesslinux/blob. This new directory is intended to take files that are only distributed as binary only large objects. My intention is to use this directory to keep non free software out of the SquashFS containers. Users will be given the opportunity to add non-free components in a very simple way. Currently the blob directory can only be used to install Adobes Flash player instead of the free Gnash player. Either place the packed install_flash_player_10_linux.tar.gz or the unpacked libflashplayer.so in the blob directory. Upcoming builds will use the blob directory to integrate closed source virus scanners and similar stuff.

Simple remaster

If you want to build an ISO with different options in the boot menu – eg. change the password hash on SSH access or place Flash player in the blob directory, first unpack the contents of the ISO image to a directory build. Then run:

        mkisofs -input-charset utf8 -r -J -pad -o "remaster.iso" \
            -V 'lesslinux-search-and-rescue' -b boot/isolinux/isolinux.bin \
            -no-emul-boot -boot-info-table -boot-load-size 4 \
            -c boot/isolinux/boot.cat build

The source

You can download all source packages from LessLinux Search and Rescue 1.5 and previous builds from distfiles.lesslinux.org. An archive containing all build scripts is available from download.lesslinux.org/src/. Instructions on building your own LessLinux based system will follow in the next days.

The penguin

Thanks to Tobias Langhammer, a friend of mine from university days, LessLinux has a new logo (its first logo to be honest). The logo shows a flying penguin (OK, a jumping penguin) and is modeled after a photograph. The logo is available under the Creative Commons Share Alike 3.0 license. I currently prefer the version with the dark background and I encourage using it for press stuff. Lighter colored versions will follow in a separate blog post.

Supporting you, supporting me

There are currently no mailing lists. You can ask questions by writing to support@mattiasschlenker.de. This Email is primarily used for paying customers, so please be so kind to wait a day or two for an answer.

If you want to support the development of LessLinux, there are certain options:

You run a company or work for a company willing to support LessLinux

I might invoice you with any sum from €5 upwards – either for support or “programming time”. If you have a EU VATIN (Value Added Tax Identification Number), the invoice will be without German VAT, and since transfers within the EU are fast and cheap, it also makes sense for small amounts. If you are located outside the EU or European Economic Area, the invoice also will be without German VAT, but the money transfer might cost significantly more, so it might just make sense for amounts of €50 upwards. Depending on the legislation in your country, invoices for development/support might be fully tax deductible.

Since LessLinux is highly customizable for many tasks like rescue, backup, distribution of images, demo systems for web based software, just ask for a quote if you have an idea.

You are a private person

If you are located within the EU, I might also write an invoice, but in this case I have to add German VAT (currently 19%). If you are outside the EU, transferring small amounts of money just does not make sense. I will investigate methods like PayPal or Amazon gifts in the near future. In the meantime: Since I like dry red wine you might send me a bottle of a local wine or – if you live north of the 51st parallel – some local beer.

• ISOhybrid conversion: Starting with version 3.8x of the Syslinux bootloader an ISO image can be prepared to be a valid hard disk image. Isolinux will boot this image in any case. There is one drawback however: A USB thumbdrive with this ISO image does not contain a writable filesystem anymore. Current LessLinux builds include a conversion routine: If sufficient RAM is found, the complete content of the ISO filessystem is copied to RAM during startup, the thumbdrive is reformatted as FAT32 and a Syslinux bootloader is written.

  To test this feature, use dd to copy the ISO to the thumbdrive: dd if=lesslinux.iso of=/dev/sdx. On Windows rename the ISO to .img and use Win32ImageWriter to perform this task.

• Start as Xen domU: With pvops Vanilla kernels getting mature it is possible to boot the same kernel on bare hardware and as Xen domU on the hypervisor. With small changes to the kernel configuration and the startup scripts (to search on Xens harddisks xvda and to open the console hvc0) LessLinux now boots on Xen. The practical usage of this feature will be for development and debugging, but it also offers the possibillity to offer lightweight live distributions as maintenance and rescue systems for hosting environments.

  To boot on Xen you must convert the initramfs files of the Vanilla Kernel 2.6.35.4 to a format that the domU loader understands — basically converting the multiple compressed cpio archives from /boot/isolinux to a single one:

  cat devs.img initram.img i2635vn.img | gunzip -c | gzip -c > initrd.img

  Then use this configuration file to fire up the domU. On pressing the Return key on hvc0 you get a simple shell where you can use ifconfig to determine the IP adress. Then use VNC to connect to the desktop of your LessLinux-domU.

  

Other new features:

• Kernel: 2.6.34.6 is default, 2.6.35.4 is optional
• Firefox: By running /opt/firefox40/lib/firefox/firefox you can start Firefox 4.0b4 with WebM support
• VLC: upgraded to 1.1.4
• Thunderbird: upgraded to 3.1.2, Enigmail and Lighning included

Known bugs:

• USB installation from the boot menu might not work, use ISOhybrid as mentioned above
• Sound will not work when booting Kernel 2.6.35.4
• Shutdown is blind due to some KMS issues
• Truecrypt manually load module fuse before running Truecrypt

Grab it here:

• Download from lesslinux.org lesslinux-search-and-rescue-uluru-20100903-134327.iso

Well it can be easier. Just configure your DSL router to forward inbound traffic on port 5500 to your desktop machine and get a nice DynDNS hostname. Then remaster any LessLinux Search and Rescue CD to include one boot entry that does not disable earlynet and add the cheatcode

        xvnc=|reverse|1280x800|24|my.dyndns.name|

In case of emergency tell your grandma to boot the CD with the respective entry. The earlynet script requests an IP address on all wired interfaces and instead of starting a local Xserver Xvnc is started and a reverse connection to your host is made where a listening VNC viewer must be running.

There is one drawback: the data is transmitted unencrypted, which might be an issue with sensitive data. You might however use this first VNC connection to build up a SSH tunnel between two hosts.

The background of this feature: I got some customers quite far away from here. With this cheatcode I can help them no matter where they are – no special configuration of their router required. This feature also will work over WLAN soon. I just introduced some cheatcodes to attach to a wireless network while startup. Those are not tested yet, so please be patient for a few more days.

Should work in all builds higher than 20100701-000000.

        nfs=192.168.1.1:/dir/containing/iso

In this case, the NFS share is mounted read only (and no locking takes place), then all ISO files down to depth 2 are searched, loop back mounted and scanned for the proper version.txt. If the system is found, the settings for toram=value take place. In reasonable fast networks you should keep this threshold low, then the start of a program via network is quick, on networks with bad latencies you might set a low threshold to copy the entire system to RAM during startup.

You might download the ISO and the sources here:

• lesslinux-search-and-rescue-uluru-20100726-105414.iso
• lesslinux-search-and-rescue-uluru-20100726-105414-buildscripts.tar.bz2

To build yourself follow the instructions in those two articles: Build stage 01 and 02 and Build stage03.

LessLinux ist ein offenes System. Mir liegt viel daran, dass eine breite Masse von Nutzern aller “Erfahrungslevel” mit den LessLinux-Systemen arbeitet, Kritik übt und Verbesserungsvorschläge beisteuert. Mir geht es dabei besonders um Feedback “normaler Nutzer”, denn dieses ist unheimlich wichtig, wenn es darum geht, ein wirklich benutzerfreundliches System auf die Beine zu stellen.

Trouble Ticket System

Seit einigen Wochen steht ein Trouble Ticket System bereit, schreiben Sie einfach eine Email an support@mattiasschlenker.de. Sie erhalten dann eine automatisch generierte Mail mit Ihrer Ticket-ID und schließlich Antwort von uns. Wir versuchen Support-Anfragen zeitnah zu beantworten, aber es kann vorkommen, dass eine Antwort einige Tage auf sich warten lässt – insbesondere dann wenn gerade an einem in Ihrer Mail angesprochenen Problem gearbeitet wird.

Support für Leser von Zeitschriften

Die Verträge mit Computerzeitschriften sehen in der Regel einen Support für einen begrenzten Zeitraum (in der Regel bis ca. 2 Monate nach Ende des Verkaufszeitraumes des Heftes) vor. Der Support erfolgt dabei üblicherweise auf zwei Ebenen:

1. Sie schreiben an die im Heft angegebene Email-Adresse für Lesersupport. Bei häufig ähnlich gestellten Fragen antworten Mitarbeiter, die von uns eingewiesen wurden.
2. Fragen, die die Redaktion nicht beantworten kann, leitet sie uns weiter, wir kümmern uns dann via Trouble Ticket System darum.

Ist das betreffende Heft schon etwas älter, können Sie den oben beschriebenen Weg direkt über das Trouble Ticket System nehmen. Wir werden auch nach Ende des offiziellen Supportzeitraumes eines Heftes keine Anfragen zurückweisen, bitten aber den folgenden Punkt zu beachten.

Wer bezahlt für den Support?

Tatsächlich finanziell gedeckt ist nur bei Zeitschriftenbeilagen der relativ kurze Zeitraum bis maximal zwei Monate nach Verkaufsende des betreffenden Heftes. Wir werden danach keine Supportanfragen abweisen – schon aus dem einfachen Grund, dass viele Supportanfragen wertvolle Hinweise für die Weiterentwicklung des Systems geben. Es gelten die oben genannten Einschränkungen hinsichtlich Antwortgeschwindigkeit.

Sollten Sie mit dem Support zufrieden sein oder einfach einen Beitrag zur Entwicklung von LessLinux leisten wollen, dürfen Sie das gerne tun. Allerdings sind PayPal-Buttons nicht unser Favorit, wir bevorzugen den klassischen Weg von Rechnung und Überweisung. Der dafür erforderliche Aufwand lohnt sich bei Beträgen ab 5 Euro netto (5,95 Euro brutto). Sollten Sie Support und Entwicklung unterstützen wollen, schicken Sie einfach eine Email mit Rechnungsadresse und Betrag an ms@mattiasschlenker.de, Sie erhalten dann postwendend eine Rechnung im PDF-Format oder auf Wunsch eine Rechnung per “gelber Post” (bitte dazuschreiben).

Support und Auftragsentwicklung für Geschäftskunden

LessLinux hat ein recht großes Potential als Notfall- und Deploymentsystem in Firmennetzen. So kann bereits heute LessLinux aus dem Netz gebootet und vom Administratordesktop aus per VNC (auch per SSH getunnelt) “ferngesteuert” werden. Mit den enthaltenen Tools lassen sich so aus der Ferne Datenrettungen oder das Deployment von Windows-Images durchführen. Von hier ist es nur ein kleiner Schritt zu angepassten Images, mit denen beispielsweise automatisches Deployment möglich ist.

Fragen Sie einfach nach, ob ein bestimmtes Feature bereits vorhanden ist oder wie groß der Aufwand wäre, dieses zu implementieren. Bei aufwendiger zu implementierenden Features kann der Aufwand auf mehrere Interessenten umgelegt werden. Die Abrechnung erfolgt in diesem Fall nach vorher vereinbartem Kostenvoranschlag, auf der Rechnung werden Entwicklungsstunden ausgewiesen, selbstverständlich ist die MwSt. ausweisbar und die Rechnung im Regelfall als Geschäftsausgabe absetzbar. Bei Interesse kontaktieren Sie bitte Mattias Schlenker per Email an ms@mattiasschlenker.de.

• lesslinux-search-and-rescue-uluru-20100528-114807.iso

Currently for netbooting a DHCP and PXE server are required, a HTTP daemon should be present, although it is possible to load the ISO directly from download.lesslinux.org. For now the ISO is completely stored in volatile memory — future versions will probably also allow NFS access. To load an ISO via HTTP just one additional parameter is necessary:

     wgetiso=http://host/path/lesslinux.iso

Of course you can use the download link above for your first tests, but please remember to change it to a local HTTP server as soon as your setup works to keep traffic at an acceptable level. Now you may combine the information from the last post with a PXE server to build a netbooting, remote accessible version of “LessLinux Search and Rescue”. Take a look at the documentation of PXELINUX and you determine when which system boots via network.

1. Setup a PXE boot environment

German speaking readers might head here, where I describe the setup of a DHCP-PXE-TFTP-boot-chain. Build the setup and test with a simple OS like memtest to confirm that it works flawlessly.

2. Copy the boot files from the LessLinux CD

Our example expects the contents of /boot/isolinux in /llsar within the TFTP root directory, so just use rsync or cp to copy all files contained in this directory.

3. Setup the boot loader

Use isolinux.cfg as a template for your entry in pxelinux.cfg/default. Make sure that earlynet is not contained in the services to skip (upcoming releses will skip this service since it waits for about 15 seconds for DHCP configuration). Then decide which options you want to add. I ended up with three entries. One for a local desktop, two to encrypted and unencrypted VNC access:

LABEL llsar
MENU LABEL LessLinux Search and Rescue LOCAL
KERNEL /llsar/l2634vn
APPEND initrd=/llsar/devs.img,/llsar/initram.img,/llsar/i2634vn.img ramdisk_size=100000 vga=788
    ultraquiet=1 security=none skipcheck=1 quiet lang=de ejectonumass=1
    skipservices=|installer|xconfgui|firewall|mountdrives| hwid=unknown laxsudo=1
    wgetiso=http://192.168.1.56/ll.iso
TEXT HELP
  Start LessLinux Search and Rescue with local desktop.
ENDTEXT

LABEL llsarvnc
MENU LABEL LessLinux Search and Rescue VNC
KERNEL /llsar/l2634vn
APPEND initrd=/llsar/devs.img,/llsar/initram.img,/llsar/i2634vn.img ramdisk_size=100000 vga=788
    ultraquiet=1 security=none skipcheck=1 quiet lang=de ejectonumass=1
    skipservices=|installer|xconfgui|firewall|mountdrives|runtimeconf| hwid=unknown laxsudo=1
    wgetiso=http://192.168.1.56/ll.iso xvnc=|remote|1280x800|24|
TEXT HELP
  Start LessLinux Search and Rescue with insecure VNC desktop.
ENDTEXT

LABEL llsarvnc
MENU LABEL LessLinux Search and Rescue SSH
KERNEL /llsar/l2634vn
APPEND initrd=/llsar/devs.img,/llsar/initram.img,/llsar/i2634vn.img ramdisk_size=100000 vga=788
    ultraquiet=1 security=none skipcheck=1 quiet lang=de ejectonumass=1
    skipservices=|installer|xconfgui|firewall|mountdrives|runtimeconf| hwid=unknown laxsudo=1
    wgetiso=http://192.168.1.56/ll.iso xvnc=|local|1280x800|24|
    rootpwhash=$1$ILXt/Dc3$DmYp.51WCDNjGuTL90eju/
TEXT HELP
  Start LessLinux Search and Rescue with VNC-over-SSH desktop.
  (SSH password is "test", please change!)
ENDTEXT

Please note that the indented lines after APPEND are part of the append parameter line. I had to break the lines to prevent the formatting from exploding. With this setup you can try the full netboot of “LessLinux Search and Rescue”.

• Booting the kernel and initramfs with PXE and loading the system ISO with wget by http or ftp
• Starting the desktop with Xvnc instead a local X server

Currently both functions just work with a wired network interface. This post covers VNC access, I will write on PXE booting later.

To test VNC access, download the latest build:

• lesslinux-search-and-rescue-uluru-20100527-082411.iso

…or build it yourself according to the last two articles withe those buildscripts and overlays (in this case the extra switch -u for unstable is necessary):

• lesslinux-search-and-rescue-uluru-20100527-082411-buildscripts.tar.bz2
• lesslinux-search-and-rescue-uluru-20100527-082411-overlays-neutral.tar.bz2

Doing it the easy way

In trusted networks, you may start Xvnc on the external interface, this means VNC access is granted without password. Just press the Tab key in the boot menu and add

        xvnc=|remote|1280x800|24|

The first value tells Xvnc to bind to the external interface, the second is the screen resolution to use (any value is accepted here), and the third parameter is the color depth. On congested networks you might reduce the depth to 16. It also makes sense to add runtimeconf to the list skipservices. When finished booting, you can connect on port 5900.

Doing it the secure way

Specifying

        xvnc=|local|1280x800|24|

tells Xvnc to bind to 127.0.0.1. So no external connections are allowed. To access, you must tunnel port 5900 over SSH. To make this possible, first remove ssh and roothash from the list skipservices, then add a roothash by specifying:

        rootpwhash=$1$ILXt/Dc3$DmYp.51WCDNjGuTL90eju/

This is the MD5 hash for the simple password test. I created this Hash with the command openssl passwd -1, Apaches htpasswd might also work. Then after the system is fully booted, you can first connect with SSH and use -L to forward :

        ssh -L 5900:localhost:5900 root@192.168.1.23

Now VNC is available on port 5900 on you local machine, simply connect this way:

        vncviewer localhost:0

The current build also is the first one to use kernel 2.6.34 and it introduces libraries from Gnome 2.30. So please test and give me feedback!