:B~ Customizing run time behaviours

1~customizing-run-time-behaviours Customizing run time behaviours

All configuration that is done during run time is done by live-config. Here
are some of the most common options of live-config that users are interested
in. A full list of all possibilities can be found in the man page of
live-config.

2~ Customizing the live user

One important consideration is that the live user is created by live-boot at
boot time, not by live-build at build time. This not only influences where
materials relating to the live user are introduced in your build, as
discussed in {Live/chroot local includes}#live-chroot-local-includes, but
also any groups and permissions associated with the live user.

You can specify additional groups that the live user will belong to by using
any of the possibilities to configure live-config. For example, to add the
live user to the #{fuse}# group, you can either add the following file in
#{config/includes.chroot/etc/live/config/user-setup.conf}#:

code{

 LIVE_USER_DEFAULT_GROUPS="audio cdrom dip floppy video plugdev netdev powerdev scanner bluetooth fuse"

}code

or use
#{live-config.user-default-groups=audio,cdrom,dip,floppy,video,plugdev,netdev,powerdev,scanner,bluetooth,fuse}#
as a boot parameter.

It is also possible to change the default username "user" and the default
password "live". If you want to do that for any reason, you can easily
achieve it as follows:

To change the default username you can simply specify it in your config:

code{

 $ lb config --bootappend-live "boot=live config username=live-user"

}code

One possible way of changing the default password is by means of a hook as
described in {Boot-time hooks}#boot-time-hooks. In order to do that you can
use the "passwd" hook from #{/usr/share/doc/live-config/examples/hooks}#,
prefix it accordingly (e.g. 2000-passwd) and add it to
#{config/includes.chroot/lib/live/config/}#

2~customizing-locale-and-language Customizing locale and language

When the live system boots, language is involved in two steps:

_* the locale generation

_* setting the keyboard configuration

The default locale when building a Live system is
#{locales=en_US.UTF-8}#. To define the locale that should be generated, use
the #{locales}# parameter in the #{--bootappend-live}# option of #{lb
config}#, e.g.

code{

 $ lb config --bootappend-live "boot=live config locales=de_CH.UTF-8"

}code

Multiple locales may be specified as a comma-delimited list.

This parameter, as well as the keyboard configuration parameters indicated
below, can also be used at the kernel command line. You can specify a locale
by #{language_country}# (in which case the default encoding is used) or the
full #{language_country.encoding}# word. A list of supported locales and the
encoding for each can be found in #{/usr/share/i18n/SUPPORTED}#.

Both the console and X keyboard configuration are performed by
#{live-config}# using the #{console-setup}# package. To configure them, use
the #{keyboard-layouts}#, #{keyboard-variants}#, #{keyboard-options}# and
#{keyboard-model}# boot parameters via the #{--bootappend-live}#
option. Valid options for these can be found in
#{/usr/share/X11/xkb/rules/base.lst}#. To find layouts and variants for a
given language, try searching for the English name of the language and/or
the country where the language is spoken, e.g:

code{

$ egrep -i '(^!|german.*switzerland)' /usr/share/X11/xkb/rules/base.lst
 ! model
 ! layout
   ch              German (Switzerland)
 ! variant
   legacy          ch: German (Switzerland, legacy)
   de_nodeadkeys   ch: German (Switzerland, eliminate dead keys)
   de_sundeadkeys  ch: German (Switzerland, Sun dead keys)
   de_mac          ch: German (Switzerland, Macintosh)
 ! option

}code

Note that each variant lists the layout to which it applies in the
description.

Often, only the layout needs to be configured. For example, to get the
locale files for German and Swiss German keyboard layout in X use:

code{

 $ lb config --bootappend-live "boot=live config locales=de_CH.UTF-8 keyboard-layouts=ch"

}code

However, for very specific use cases, you may wish to include other
parameters. For example, to set up a French system with a French-Dvorak
layout (called Bepo) on a TypeMatrix EZ-Reach 2030 USB keyboard, use:

code{

 $ lb config --bootappend-live \
     "boot=live config locales=fr_FR.UTF-8 keyboard-layouts=fr keyboard-variants=bepo keyboard-model=tm2030usb"

}code

Multiple values may be specified as comma-delimited lists for each of the
#{keyboard-*}# options, with the exception of #{keyboard-model}#, which
accepts only one value. Please see the #{keyboard(5)}# man page for details
and examples of #{XKBMODEL}#, #{XKBLAYOUT}#, #{XKBVARIANT}# and
#{XKBOPTIONS}# variables. If multiple #{keyboard-variants}# values are
given, they will be matched one-to-one with #{keyboard-layouts}# values (see
#{setxkbmap(1)}# #{-variant}# option). Empty values are allowed; e.g. to
define two layouts, the default being US QWERTY and the other being US
Dvorak, use:

code{

 $ lb config --bootappend-live \
     "boot=live config keyboard-layouts=us,us keyboard-variants=,dvorak"

}code

2~persistence Persistence

A live cd paradigm is a pre-installed system which runs from read-only
media, like a cdrom, where writes and modifications do not survive reboots
of the host hardware which runs it.

A Debian Live system is a generalization of this paradigm and thus supports
other media in addition to CDs; but still, in its default behaviour, it
should be considered read-only and all the run-time evolutions of the system
are lost at shutdown.

'Persistence' is a common name for different kinds of solutions for saving
across reboots some, or all, of this run-time evolution of the system. To
understand how it works it would be handy to know that even if the system is
booted and run from read-only media, modifications to the files and
directories are written on writable media, typically a ram disk (tmpfs) and
ram disks' data do not survive reboots.

The data stored on this ramdisk should be saved on a writable persistent
medium like local storage media, a network share or even a session of a
multisession (re)writable CD/DVD. All these media are supported in Debian
Live in different ways, and all but the last one require a special boot
parameter to be specified at boot time: #{persistence}#.

If the boot parameter #{persistence}# is set (and #{nopersistence}# is not
set), local storage media (e.g. hard disks, USB drives) will be probed for
persistence volumes during boot. It is possible to restrict which types of
persistence volumes to use by specifying certain boot parameters described
in the live-boot(7) man page. A persistence volume is any of the following:

_* a partition, identified by its GPT name.

_* a filesystem, identified by its filesystem label.

_* an image file located on the root of any readable filesystem (even an
NTFS partition of a foreign OS), identified by its filename.

The volume label for overlays must be #{persistence}# but it will be ignored
unless it contains in its root a file named #{persistence.conf}# which is
used to fully customize the volume's persistence, this is to say, specifying
the directories that you want to save in your persistence volume after a
reboot. See {The persistence.conf file}#persistence-conf for more details.

Here are some examples of how to prepare a volume to be used for
persistence. It can be, for instance, an ext4 partition on a hard disk or on
a usb key created with, e.g.:

code{

 # mkfs.ext4 -L persistence /dev/sdb1

}code

See also {Using the space left on a USB stick}#using-usb-extra-space.

If you already have a partition on your device, you could just change the
label with one of the following:

code{

 # tune2fs -L persistence /dev/sdb1 # for ext2,3,4 filesystems

}code

Here's an example of how to create an ext4-based image file to be used for
persistence:

code{

 $ dd if=/dev/null of=persistence bs=1 count=0 seek=1G # for a 1GB sized image file
 $ /sbin/mkfs.ext4 -F persistence

}code

Once the image file is created, as an example, to make #{/usr}# persistent
but only saving the changes you make to that directory and not all the
contents of #{/usr}#, you can use the "union" option. If the image file is
located in your home directory, copy it to the root of your hard drive's
filesystem and mount it in #{/mnt}# as follows:

code{

 # cp persistence /
 # mount -t ext4 /persistence /mnt

}code

Then, create the #{persistence.conf}# file adding content and unmount the
image file.

code{

 # echo "/usr union" >> /mnt/persistence.conf
 # umount /mnt

}code

Now, reboot into your live medium with the boot parameter "persistence".

3~persistence-conf The persistence.conf file

A volume with the label #{persistence}# must be configured by means of the
#{persistence.conf}# file to make arbitrary directories persistent. That
file, located on the volume's filesystem root, controls which directories it
makes persistent, and in which way.

How custom overlay mounts are configured is described in full detail in the
persistence.conf(5) man page, but a simple example should be sufficient for
most uses. Let's say we want to make our home directory and APT cache
persistent in an ext4 filesystem on the /dev/sdb1 partition:

code{

 # mkfs.ext4 -L persistence /dev/sdb1
 # mount -t ext4 /dev/sdb1 /mnt
 # echo "/home" >> /mnt/persistence.conf
 # echo "/var/cache/apt" >> /mnt/persistence.conf
 # umount /mnt

}code

Then we reboot. During the first boot the contents of #{/home}# and
#{/var/cache/apt}# will be copied into the persistence volume, and from then
on all changes to these directories will live in the persistence
volume. Please note that any paths listed in the #{persistence.conf}# file
cannot contain white spaces or the special #{.}# and #{..}# path
components. Also, neither #{/lib}#, #{/lib/live}# (or any of their
sub-directories) nor #{/}# can be made persistent using custom mounts. As a
workaround for this limitation you can add #{/ union}# to your
#{persistence.conf}# file to achieve full persistence.

Several different custom overlay volumes (with their own
#{persistence.conf}# files) can be used at the same time, but if several
volumes make the same directory persistent, only one of them will be
used. If any two mounts are "nested" (i.e. one is a sub-directory of the
other) the parent will be mounted before the child so no mount will be
hidden by the other. Nested custom mounts are problematic if they are listed
in the same #{persistence.conf}# file. See the persistence.conf(5) man page
for how to handle that case if you really need it (hint: you usually don't).

3~ Using more than one persistence store

If a user would need multiple persistence store of the same type for
different locations or testing, such as #{persistence-private}# and
#{persistence-work}#, the boot parameter #{persistence-label}# used in
conjunction with the boot parameter #{persistence}# will allow for multiple
but unique persistence media. An example would be if a user wanted to use a
persistence partition labeled #{persistence-subText}# they would use the
boot parameters of: #{persistence}# #{persistence-label=subText}#.
