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remastering-old [2011/10/13 21:55] (current)
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 +====== Remastering grml from an existing ISO ======
  
 +**Note:** The **current version** of this document is at [[remastering]].
 +
 +This page documents the **manual** remastering approach which was used for older grml versions (year 2007 and before).
 +
 +===== Tip of the day =====
 +
 +Note: **[[http://grml.org/grml-live/|grml-live]]** is a new framework (based on [[http://fai-project.org|FAI]]) for creating your own Linux Live-CD based on Debian/grml. Instead of remastering an existing grml-ISO (like described below) you can create a fully customized version from scratch.
 +
 +Moreover, you can use it to create [[Stacked Grml]].
 +
 +
 +However, if you decide to use the method below, **be aware that the latest versions of GRML use lzma compression** instead of gzip with squashfs, so systems like Fedora9 (without some work) will not be able to unpack the image.  Boot from an un-remastered version and use its squash utils. See [[http://grml.org/grml-live/#current_state|http://grml.org/grml-live/#current_state]] for more details.
 +
 +Also, if mksquashfs hangs at the same place each time, it is probably this [[https://bugs.launchpad.net/ubuntu/+source/squashfs/+bug/222700|bug]].  Use -no-sparse to get around it.
 +
 +===== Copying / =====
 +
 +Hint before you begin:\\
 +You can remaster grml on grml itself! Just install grml to harddisk with grml2hd and have a nice environment to remaster grml with this. Doing it this way has the advantage that you have support for squashfs etc. builtin. Furthermore, the kernel-modules and headerfiles inside the chroot fit to your running kernel. This is helpful if you want to integrate applications like VMware into grml.
 +
 +To get access to grml's /, you first have to mount the grml_X.Y.iso somewhere. This ISO image is a iso9660 filesystem - any recent distribution kernel should include support for iso9660.
 +
 +I put all my remastering stuff under ''~/grml-remaster'', just to keep track of all the files. So create a mount point and mount the iso image:
 +
 +  $ mkdir -p ~/grml-remaster/mount1 # We will create another mountpoint, hence the '1' at the end 
 +  $ sudo mount /path/to/grml-X.Y.iso ~/grml-remaster/mount1 -o loop
 +
 +Now we have the CD image mounted at ''mount1/''. Inside the cd image there's e.g. the isolinux stuff, the index.html (which you get displayed when you put grml into a windows pc) and a file called ''GRML'' in the directory ''GRML''. This file contains grml's root file system and is a squashfs filesystem.
 +
 +The rest of this procedure depends on whether you intend to change the contents of the sqashfs filesystem or not. Since grml is very flexible, there are chances that you do not need to modify the squashfs.
 +
 +===== Remaster while keeping the original squashfs =====
 +
 +You can start exploring the grml CD's / in ''~/grml-remaster/mount1'' right now. Beware that the file system is mounted read-only, as iso9660 is a read-only filesystem (anything else wouldn't make sense on the CD, either :-)).
 +
 +To make changes, we have to copy the mounted CD. I created ''~/grml-remaster/copy-mount1'' for this and copied ''mount1/'' there:
 +  $ mkdir ~/grml-remaster/copy-mount1
 +  $ cp -av ~/grml-remaster/mount1/* ~/grml-remaster/copy-mount1
 +
 +This takes some time. After cp is finished you have a read-/writeable copy of the grml CD's ''/'' in ''~/grml-remaster/copy-mount1''. You may umount ''~/grml-remaster/mount1'' now, if you wish.
 +
 +After making your changes, create a new .iso:
 +  $ cd copy-mount1
 +  $ mkisofs -V "locally modified grml" -publisher 'Your Name <your.address@example>' -l -r -J \
 +    -no-emul-boot -boot-load-size 4 -boot-info-table -c boot/isolinux/boot.cat -b \
 +    boot/isolinux/isolinux.bin -o ../my-local-grml.iso .
 +
 +
 +===== Remaster with modified squashfs =====
 +
 +You need to apply the [[http://squashfs.sourceforge.net/|kernel patch for SquashFS]] to your kernel sources and set ''CONFIG_SQUASHFS'' to ''m'' or ''y'' to make your kernel squashfs-ready. Don't panic, you don't have to reboot for it. ;-) ''make modules && sudo make modules_install'' will work fine if you set ''CONFIG_SQUASHFS'' to ''m''.
 +
 +**Important:** please notice that the squashfs version needed for remastering grml strongly depends on which version of grml you are remastering. Current grml versions us squashfs with lzma compression. Check out [[http://git.grml.org/?p=grml-kernel.git|grml-kernel git repository]], [[http://git.grml.org/?p=squashfs-lzma.git|squashfs-lzma at grml]] and [[http://www.squashfs-lzma.org/|squashfs-lzma at upstream]]. Reminder: check out [[http://grml.org/grml-live/#current_state|current state at grml-live documentation]].
 +
 +So, for example:
 +
 +  $ cd /usr/src
 +  $ wget http://mesh.dl.sourceforge.net/sourceforge/squashfs/squashfs2.2-r2.tar.gz
 +  $ tar xvzf squashfs2.2-r2.tar.gz
 +  $ cd /lib/modules/`uname -r`/build
 +  $ patch -p1 --dry-run < /usr/src/squashfs2.2-r2/linux-2.X.Y/squashfs2.2-patch
 +  Check, if the patch succeeded. --dry-run is generally a good idea. If everything went fine:
 +  $ patch -p1 < /usr/src/squashfs2.2-r2/linux-2.X.Y/squashfs2.2-patch
 +  $ make menuconfig
 +  (enable SquashFS)
 +  $ make modules
 +  $ sudo make modules_install
 +  $ sudo modprobe squashfs
 +
 +Now your kernel is ready for squashfs. You can verify this with ''grep squashfs /proc/filesystems''.
 +
 +Next, mount the grml root file system. I created ''~/grml-remaster/mount2'' for this.
 +  $ mkdir ~/grml-remaster/mount2
 +  $ sudo mount ~/grml-remaster/mount1/GRML/GRML ~/grml-remaster/mount2 -o loop -t squashfs
 +
 +You can start exploring grml's / in ''~/grml-remaster/mount2'' right now. Beware that the file system is mounted read-only, as squashfs is a read-only filesystem (anything else wouldn't make sense on the CD, either :-)).
 +
 +To make changes to the grml filesystem, we have to copy the mounted ''/''. I created ''~/grml-remaster/copy-mount2'' for this and copied ''mount2/'' there:
 +  $ mkdir ~/grml-remaster/copy-mount2
 +  $ sudo cp -av ~/grml-remaster/mount2/* ~/grml-remaster/copy-mount2
 +
 +This takes some time. After cp is finished you have a read-/writeable copy of grml's ''/'' in ''~/grml-remaster/copy-mount2''. You may umount ''~/grml-remaster/mount2'' now, if you wish.
 +
 +==== Making changes ====
 +
 +You can treat ''~/grml-remaster/copy-mount2'' like a root filesystems of an installed linux (in fact, it isn't something else).
 +
 +You can just copy files there or chroot into it, to run apt-get or so.
 +  $ sudo chroot ~/grml-remaster/copy-mount2 /usr/bin/zsh
 +  root@foo ~ #
 +  (do whatever you like to do with grml)
 +  [you might to need
 +  root@foo ~ # mount -t proc none /proc
 +  root@foo ~ # mount -t devpts none /dev/pts
 +  for some actions, don't forget to umount /proc && umount /dev/pts before leaving the chroot]
 +  root@foo ~ # exit
 +  $
 +
 +This is straightforward. You may consult any knoppix remastering howto (like [[http://www.knoppix.net/wiki/Knoppix_Remastering_Howto|the one on knoppix.net]]) to find out how to remove unnecessary packages (but hey, are there really any? ;-)) or install new ones. If you are familiar with Debian, feel at home.
 +
 +==== Putting the changes back ====
 +
 +You have to create a new squashfs image (the huge ''GRML/GRML'' file), for which ''mksquashfs'' is needed. You may build it by yourself (see ''/usr/src/squashfs2.2-r2/squashfs-tools'', if you followed the steps above) or, if you are on a Debian system, just ''apt-get install squashfs-tools''. Please note that filesystems generated whith squashfs-tools 3.x are not backwards compatible to version 2.x of squashfs which for instance is used by grml-small 0.4. If your remastered cd fails to find a grml-image, check ''mksquashfs -version'' .
 +
 +Next, ''mksquashfs'' is ran with the source directory and the destination file as arguments:
 +  You should do this as root, else mksquashfs can't read all files:
 +  $ sudo mksquashfs ~/grml-remaster/copy-mount2 ~/grml-remaster/new-GRML
 +You can additionally add ''-info'' to **the end** of the command line to get some additional information about the state of the build process. The building of the squashfs image takes some time again. (Note: ThereĀ“s a little bug in mksquashfs 3.3 - which is shipped in grml64-0.2 - resulting mksquashfs running in a deadlock. You should add the option ''-no-sparse''. [[http://sourceforge.net/mailarchive/message.php?msg_name=oyd63wy5374.fsf%40cs.rice.edu|SquashFS-Devel-Mailinglist]])
 +
 +When ''mksquashfs'' is finished, you should have a look at ''~/grml-remaster/new-GRML''. If it's too large and unlikely to fit on a CD-R and you should remove some packages or files.
 +
 +You **may** remove ''~/grml-remaster/copy-mount2'' at this point, but beware that you can easily re-create ''~/grml-remaster/new-GRML'' out of it anything goes (or even already went) wrong.
 +
 +The next step is to put the ''new-GRML'' into an iso9660 image. The original image is mounted at ''~/grml-remaster/mount1'' -- read-only, of course. So to replace files (the ''GRML/GRML''), we have to copy it:
 +  $ mkdir ~/grml-remaster/copy-mount1
 +  $ rsync -av --exclude=GRML/GRML ~/grml-remaster/mount1/. ~/grml-remaster/copy-mount1
 +We use rsync here, so we can --exclude ''GRML/GRML'' -- as it gets replaced anyway.
 +
 +You may umount ''~/grml-remaster/mount1/'' now, if you wish.
 +
 +Next, put new-GRML back to the iso9660 root:
 +  $ mv ~/grml-remaster/new-GRML ~/grml-remaster/copy-mount1/GRML/GRML
 +
 +You should update the md5sums in ''GRML/md5sums'' to make automatic checking tools happy. I am lazy and just overwrite ''./GRML'''s entry.
 +  $ md5sum ~/grml-remaster/copy-mount1/GRML/GRML
 +  057dba8064085c10e90b1291fcbe418d  /home/foobar/grml-remaster/copy-mount1/GRML/GRML
 +  $ chmod 644 ~/grml-remaster/copy-mount1/GRML/md5sums # this file is mode 444, as the CD was r/o.
 +  $ vim ~/grml-remaster/copy-mount1/GRML/md5sums
 +  (change the line)
 +  $
 +
 +At the last step, you have to create the iso9660 image. You have to supply mkisofs some additional information, e.g. the path to isolinux.
 +  $ mkisofs -pad -l -r -J -v -V "grml X.Y" -no-emul-boot \
 +    -boot-load-size 4 -boot-info-table \
 +    -b boot/isolinux/isolinux.bin -c boot/isolinux/boot.cat \
 +    -hide-rr-moved \
 +    -o ~/grml-remaster/grml_X.Y-remastered.iso \
 +    ~/grml-remaster/copy-mount1
 +   (...)
 +   xxxxxxx extents written (yyy MB)
 +  $
 +
 +Congratulations. Delete ~/grml-remaster/copy-mount2 if you want and try out your remastered grml image in ''~/grml-remaster/grml_X.Y-remastered.iso'' with qemu, vmware or with CD-RW on real hardware.
 + 
 +===== Copyright =====
 +
 +I, Sebastian Schmidt (<yath-grmlwiki@yath.de>), hereby put this text into the public domain. Do with it what you like.
 +Some modifications by Marc Haber and Michael Prokop are also in the public domain.
 
remastering-old.txt · Last modified: 2011/10/13 21:55 (external edit)
 
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