Disk Preparation

Partition Debian disks with PXE and shell script(s) instead of complex preseed partman templates.

Advanced partitioning of Debian boxes with preseed templates can be a challange. disk-preparation makes it easy to bypass, simplify or extend the built-in templates by writing shell script(s) to prepare and partition your disks. It is possible to completely disable partman in the Debian installer.

This package is like a three stage rocket:

The preseed's early_command is used to download an udeb package and add it to the Installer system.
The udeb's postinst script will be run between Detect disks and Partition disks (partman).
The postinst will download a script or program called disk-preparation and run it.

The download supports both TFTP and HTTP(S).

Both the udeb package and the disk-preparation should be placed at the same location as the preseed file. Both the preseed examples below and the postinst script will extract the preseed location from the boot command line and use the same location.

Building

Packages are built with debhelper's dh_builddeb command.

Prerequisites

To learn about the debconf system (not needed to build the udeb package):

apt-get install debconf-doc

To build udeb using dh_builddeb

apt-get install --no-install-recommends debhelper build-essential

To update debian/changelog from the git log:

apt-get install --no-install-recommends git-buildpackage libdistro-info-perl

Update changelog

The following command will extract commit messages from the git log and put them in a changelog entry. --full includes all lines from commit messages, not just the first line. --spawn-editor=always allows for editing of the changelog before it is saved to debian/changelog.

Note that the version string at the top line of the changelog will be the version of the package file reglardless of settings in the debian/control file.

$ gbp dch --git-author --urgency=low --ignore-branch --full --spawn-editor=always --release --since=<git-hash>

Build the package

$ dh_builddeb

Note that the newly built package will be placed in the parent directory (../).

Boot information during install

To find out the download path extracted from the boot command, switch to a shell terminal during installation, e.g.: CTRL-F2.

$ sed -n 's#.*url=\([^ ]\+/\).*#\1#p' /proc/cmdline

Specifying script source location

This can be specified on the kernel command line:

url=http://some.host/some.file

Or alternatively you can use the preseed variable my-disk-prep/url

d-i my-disk-prep/url string http://some.host/some.file

Preseed configuration

The disk-preparation udeb package can be downloaded and added from preseed/early_command, e.g.:

d-i preseed/early_command string                                          \
    MYTAG="my-early_command" ; pkgname="disk-preparation_1.0_all.udeb" ;  \
    DLURL=$( sed -n 's#.*url=\([^ ]\+/\).*#\1#p' /proc/cmdline ) &&       \
    logger -t "$MYTAG" "DLURL extracted from /proc/cmdline: $DLURL" &&    \
    DLMETHOD=$( echo $DLURL | cut -d':' -f1 | tr 'a-z' 'A-Z' ) &&         \
    logger -t "$MYTAG" "DLMETHOD extracted from \$DLURL: $DLMETHOD" &&    \
    DLPATH="/tmp/my-stuff" && mkdir $DLPATH &&                            \
    if [ "x$DLMETHOD" = "xTFTP" ] ; then                                  \
      PRT=$( echo $DLURL | sed -n 's#.*//\([^/]\+\)/\(.*\)$#\1:\2#p' ) && \
      DLHOST=$( echo $PRT | cut -d':' -f1 ) &&                            \
      logger -t "$MYTAG" "TFTP server: $DLHOST" &&                        \
      DLURL=$( echo $PRT | cut -d':' -f2 ) &&                             \
      logger -t "$MYTAG" "Server path: $DLURL" &&                         \
      logger -t "$MYTAG" "Downloading $pkgname using tftp command." &&    \
      tftp -l $DLPATH/$pkgname -g $DLHOST -r $DLURL/$pkgname || exit $? ; \
    else                                                                  \
      logger -t "$MYTAG" "Downloading $pkgname using wget command." &&    \
      wget -P $DLPATH/ $DLURL/$pkgname | exit $? ;                        \
    fi ;                                                                  \
    logger -t "$MYTAG" "Adding $pkgname to the installer system." &&      \
    udpkg --unpack $DLPATH/$pkgname &&                                    \
    logger -t "$MYTAG" "End of early_command, continuing the installation."

Or use the early-wrapper.sh script from the preseed to be able to change debconf priority, add the udeb to the Installer system, run additional scripts as soon as preseed file has been loaded:

d-i preseed/early_command string                                           \
    MYTAG="my-early_command" ; escript="early-wrapper.sh" ;                \
    export DLURL=$( sed -n 's#.*url=\([^ ]\+/\).*#\1#p' /proc/cmdline ) && \
    logger -t "$MYTAG" "DLURL extracted from /proc/cmdline: $DLURL" &&     \
    export DLMETHOD=$( echo $DLURL | cut -d':' -f1 | tr 'a-z' 'A-Z' ) &&   \
    logger -t "$MYTAG" "DLMETHOD extracted from \$DLURL: $DLMETHOD" &&     \
    export DLPATH="/tmp/my-stuff" && mkdir $DLPATH &&                      \
    if [ "x$DLMETHOD" = "xTFTP" ] ; then                                   \
      PRT=$( echo $DLURL | sed -n 's#.*//\([^/]\+\)/\(.*\)$#\1:\2#p' ) &&  \
      export DLHOST=$( echo $PRT | cut -d':' -f1 ) &&                      \
      logger -t "$MYTAG" "TFTP server: $DLHOST" &&                         \
      export DLURL=$( echo $PRT | cut -d':' -f2 ) &&                       \
      logger -t "$MYTAG" "Server path: $DLURL" &&                          \
      logger -t "$MYTAG" "Downloading $escript using tftp command." &&     \
      tftp -l $DLPATH/$escript -g $DLHOST -r $DLURL/$escript || exit $? ;  \
    else                                                                   \
      logger -t "$MYTAG" "Downloading $escript using wget command." &&     \
      wget -P $DLPATH/ $DLURL/$escript || exit $? ;                        \
    fi ;                                                                   \
    logger -t "$MYTAG" "Starting $escript" &&                              \
    chmod +x $DLPATH/$escript && $DLPATH/$escript &&                       \
    logger -t "$MYTAG" "End of early_command, continuing the installation."

#
# My own "d-i" varaibles used by early-wrapper.sh:
# The variable $ MYTAG is set to "my-stuff" in most of my scripts and will be
# used for logger messages and for my own configuration variables in debconf.
#
# The debconf priority we like to continue with after inital network setup.
# To have automated install, "priority=high" is enough after network is
# configured.
# To boot with DHCP and avoid network questions before the preseed file is
# loaded, the boot commandline must have "priority=critical".
# After the inital network config we can change to our preferred priority.
# With "medium" or "low" we will see the installer menus even if options are
# set by the preseed file. Can be used for debugging or updates of preseed file.
d-i my-stuff/early-wrapper/newprio string high
#
# A list of udeb(s) to unpack (add to the installer system).
# Udebs will only be unpacked, not fully installed until relevant stage in
# the installer system depening on 'Installer-Menu-Item' in udeb's control file.
d-i my-stuff/early-wrapper/udeb-unpack string disk-preparation_1.0_all.udeb
#
# Additional scripts to run from early-wrapper.sh:
#d-i my-stuff/early-wrapper/earlyscripts string early-extra-1.sh early-extra-2.sh

Providing disk preparation script inline in the preseed file

To provide the partitioning script inline in the preseed file, use the special URL preseed:, then have the following in the preseed file:

### disk-preparation script begin
# #!/bin/sh
#
# # specify commands here, with a leading '# ' to prevent preseed from trying
# # to parse the lines
#
# # partition disks
# log-output -t $TAG partitioning disks
# anna-install parted-udeb
#
# # etc. etc.
#
### disk-preparation script end