Debian Live マニュアル　日本語版

7 Live 動作環境

7.1. Swap space

FIXME

7.2. Hostname

FIXME

7.3. The Live user

Username FIXME.

One important consideration is that the live user is created by
live-initramfs during bootup, it is not created by live-helper
when building the image.

You can specify additional groups that the live user will belong
to by preseeding the passwd/user-default-groups debconf value.
For example, to add the live user to the fuse group, add the
following to a file in the config/chroot_local-preseed
directory:

debconf passwd/user-default-groups string audio cdrom dialout floppy video plugdev netdev powerdev fuse

For more information about debconf preseeding, please see
Section 5.2.3, ?Preseeding Debconf questions?.

7.4. Language

When the live system boots there are three process which
concerns language: the locale generation, setting the keyboard
layout for the console and setting the keyboard layout for X. To
define the locale that should be generated, use the locale
parameter to the --bootappend-live option of lh_config, e.g.:

lh_config --bootappend-live "locale=sv_SE.utf8"

Both the console and X keyboard configuration depends on the
keyb parameter of the --bootappend-liveoption. Valid options for
X keyboard layouts can be found in /etc/X11/xkb/base.xml. To
find the value (the two characters) corresponding to a language
try searching for the english name of the nation where the
language is spoken, e.g:

$ grep -i sweden -C3 /etc/X11/xkb/base.xml | grep name

<name>se</name>

To get the locale files for swedish generated and a swedish
keyboard layout in X use:

lh_config --bootappend-live "locale=sv_SE.utf8 keyb=se"

A list of the valid values of the keyboards for the console can
be figured with the following command:

for i in `find /usr/share/keymaps/ -iname "*kmap.gz"`; do basename $i | head -c -9; echo; done | sort | less

To make the console keyboard use a swedish layout use

lh_config --bootappend-live "locale=sv_SE.utf8 keyb=se-latin1"

7.5. Persistence

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

A Debian Live system is a generalization of this paradigm and
thus supports more media, and not only cds; but stills, in its
default behaviour, it should be considered read only and all the
runtime evolutions of the system are lost with a shutdown.

Persistence is a common name for different kinds of solutions
for saving across reboots some or all of this runtime evolution
of the system; to undestand how it could work it could be handy
to know that even if the system is booted and runt from a read
only media, modification to the files and directories are wrote
on a writable media, typically a ram disk (tmpfs) and ram disk's
data do not survive reboots.

The data stored on this ramdisk should be saved in a writable
persistent media like on an Hard Disk, a USB key, a network
"share" or even a session of a multisession (re)writable CD/DVD.
All this cited media are supported in Debian Live in different
ways, all but latest one requires a special boot parameter to be
specified at boot: persistent.

7.5.1. Full persistence

With "full persistence" it is meant that instead of using a
tmpfs for storing modifications to the read-only media (with the
copy-on-write, COW, system) a writable partition is used. In
order to use this feature a partition with a clean writable
supported filesystem on it labeled "live-rw" must be attached on
the system at bootime and the system must be started with
"persistent" boot parameter; this partition could be an ext2
partition on the hard disk or on a usb key created with, e.g.:

# mkfs.ext2 -L live-rw /dev/sdb1

But since live system users, not always can use an hard drive
partition, maybe because they aren't allowed or they wan't to
repartition a drive, and considering that most USB keys have
laughables write speeds, "full" persistence could be also used
with just image files, so you could create a file representing a
partition and put this image file even on a NTFS partition of a
foreign OS, with something like:

$ dd if=/dev/null of=live-rw bs=1G seek=1 # for a 1GB sized image file
$ /sbin/mkfs.ext2 -F live-rw

Then copy the live-rw file in a writable partition and reboot
with "persistent" boot parameter.

7.5.2. Home automounting

If during the boot a partition (filesystem) image file or a
partition labeled home-rw will be discovered, this filesystem
will be directly mounted as /home, thus permitting persistence
of files that belong to the e.g. default user. It can be
combined with full persistence.

7.5.3. Snapshots

Snapshots are collection of files and directories which are not
mounted while running but which are copied from a persistent
device to the system (tmpfs) at boot and which are resynced at
reboot/shutdown of the system. The content of a snapshot could
reside on a partition or an image file (like the above mentioned
types) labeled live-sn, but it defaults to a simple cpio archive
named live-sn.cpio.gz. As above at boot time, the block devices
connected to the system are traversed to see if a partition or a
file named like that could be found. A power interruption during
runtime could lead to data lost hence a tool invoked
live-snapshot --refresh could be called to sync important
changes. This type of persistence since it does not write
continuosly to the persistent media is the most flash-based
device friendly and the fastest of all the persistence systems.

A /home version of snapshot exists too and its label is
home-sn.*; it works the same as the main snapshot but it is only
applied to /home.

All kind of snapshots cannot currently handle file deleting
while full persistence and obviously home automounting could.

7.5.4. Partial remasterings

The runtime modification of the tmpfs could be collected usign
live-snapshot in a squashfs and added to the cd by remastering
the iso in case of cd-r or adding a session to multisession cd/
dvd(rw); live-initramfs mounts all /live filesystem in order or
with the module bootparameter.