Ubuntu Manpage: live-boot - System Boot Components

Provided by: live-boot-doc_20210208_all

NAME

       live-boot - System Boot Components

DESCRIPTION

       live-boot contains the components that configure a live system during the boot process (early userspace).

       live-boot  is  a hook for the initramfs-tools, used to generate a initramfs capable to boot live systems,
       such as those created by live-helper(7). This includes the Live systems ISOs, netboot tarballs,  and  usb
       stick images.

       At  boot  time  it  will  look  for  a  (read-only)  medium  containing  a "/live" directory where a root
       filesystems (often a compressed filesystem image like squashfs) is stored. If found,  it  will  create  a
       writable environment, using aufs, to boot the system from.

CONFIGURATION

       live-boot can be configured through a boot parameter or a configuration file.

       To  configure  the live-boot parameters used by default in a live image, see the --bootappend-live option
       in the lb_config(1) manual page.

   Kernel Parameters
       live-boot is only activated if 'boot=live' was used as a kernel parameter.

       In addition, there are some more boot parameters to influence the behaviour, see below.

   Configuration Files
       live-boot can be configured (but not activated) through configuration files. Those files  can  be  placed
       either  in  the  root  filesystem  itself  (/etc/live/boot.conf,  /etc/live/boot/*), or on the live media
       (live/boot.conf, live/boot/*).  These environment variables can only be set in the configuration files:

       DISABLE_CDROM=[true|false]
              Disable support for booting from CD-ROMs.  If set to 'true' mkinitramfs will  build  an  initramfs
              without the kernel modules for reading CD-ROMs.

       DISABLE_FAT=[true|false]
              Disable  support  for  booting  from FAT file systems.  If set to 'true' mkinitramfs will build an
              initramfs without the kernel module vfat and some nls_* modules.

       DISABLE_FUSE=[true|false]
              Disable support for booting from FUSE-based file systems.  If set to 'true' mkinitramfs will build
              an initramfs without the kernel module fuse and file systems that depend on it (like curlftpfs and
              httpfs2).

       DISABLE_NTFS=[true|false]
              Disable support for booting from NTFS file systems.  If set to 'true' mkinitramfs  will  build  an
              initramfs without the kernel module ntfs.

       DISABLE_USB=[true|false]
              Disable  support  for  booting  from  USB  devices.   If  set  to 'true' mkinitramfs will build an
              initramfs without the kernel module sd_mod.

       MINIMAL=[true|false]
              Build a minimal initramfs.  If set to 'true' mkinitramfs will build an initramfs without some udev
              scripts and without rsync.

       PERSISTENCE_FSCK=[true|false]
              Run  fsck on persistence filesystem on boot. Will attempt to repair errors. The execution log will
              be saved in /var/log/live/fsck.log.

       FSCKFIX=[true|false]
              If PERSISTENCE_FSCK or forcefsck are set, will pass -y to fsck to stop it  from  asking  questions
              interactively and assume yes to all queries.

OPTIONS

live-boot currently features the following parameters.

access=ACCESS
Set the accessibility level for physically or visually impaired users. ACCESS must be one of v1, v2,
v3, m1, or m2. v1=lesser visual impairment, v2=moderate visual impairment, v3=blindness, m1=minor
motor difficulties, m2=moderate motor difficulties.

console=TTY,SPEED
Set the default console to be used with the "live-getty" option. Example: "console=ttyS0,115200"

debug
Makes initramfs boot process more verbose.
Use: debug=1
Without setting debug to a value the messages may not be shown.

fetch=URL

httpfs=URL
Another form of netboot by downloading a squashfs image from a given URL. The fetch method copies
the image to RAM and the httpfs method uses FUSE and httpfs2 to mount the image in place. Copying to
RAM requires more memory and might take a long time for large images. However, it is more likely to
work correctly because it does not require networking afterwards and the system operates faster once
booted because it does not require to contact the server anymore.
Due to current limitations in busybox's wget and DNS resolution, an URL can not contain a hostname
but an IP address only.
Not working: http://example.com/path/to/your_filesystem.squashfs
Working: http://1.2.3.4/path/to/your_filesystem.squashfs
Also note that therefore it's currently not possible to fetch an image from a name-based virtualhost
of an httpd if it is sharing the IP address with the main httpd instance.
You may also use the live ISO image in place of the squashfs image.

iscsi=server-ip[,server-port];target-name
Boot from an iSCSI target that has an ISO or disk live image as one of its LUNs. The specified target
is searched for a LUN which looks like a live medium. If you use the iscsitarget software iSCSI
target solution your ietd.conf might look like this:
# The target-name you specify in the iscsi= parameter
Target <target-name>
Lun 0 Path=<path-to-your-live-image.iso>,Type=fileio,IOMode=ro
# If you want to boot multiple machines you might want to look at tuning some parameters like
# Wthreads or MaxConnections

findiso=/PATH/TO/IMAGE
Look for the specified ISO file on all disks where it usually looks for the .squashfs file (so you
don't have to know the device name as in fromiso=....).

forcefsck
Run fsck on persistence filesystem on boot. Will attempt to repair errors. The execution log will be
saved in /var/log/live/fsck.log.

fromiso=/PATH/TO/IMAGE
Use a filesystem from within an ISO image that's available on live-media. The first part of the
argument should be the block device where the image is stored, followed by the path and filename
(e.g. fromiso=/dev/sda1/live/image.iso).
Alternatively, it can be used to boot from an ISO embedded into an initrd (e.g.
fromiso=/live/image.iso).

ignore_uuid
Do not check that any UUID embedded in the initramfs matches the discovered medium. live-boot may be
told to generate a UUID by setting LIVE_GENERATE_UUID=1 when building the initramfs.

verify-checksums
If specified, an MD5 sum is calculated on the live media during boot and compared to the value found
in md5sum.txt found in the root directory of the live media.

ip=[DEVICE]:[CLIENT_IP]:[NETMASK]:[GATEWAY_IP]:[NAMESERVER]
[,[DEVICE]:[CLIENT_IP]:[NETMASK]:[GATEWAY_IP]:[NAMESERVER]]
Let you specify the name(s) and the options of the interface(s) that should be configured at boot
time. Do not specify this if you want to use dhcp (default). It will be changed in a future release
to mimic official kernel boot param specification (e.g.
ip=10.0.0.1::10.0.0.254:255.255.255.0::eth0,:::::eth1:dhcp).

ip=[frommedia]
If this variable is set, dhcp and static configuration are just skipped and the system will use the
(must be) media-preconfigured /etc/network/interfaces instead.

{live-media|bootfrom}=DEVICE
If you specify one of this two equivalent forms, live-boot will first try to find this device for the
"/live" directory where the read-only root filesystem should reside. If it did not find something
usable, the normal scan for block devices is performed.
Instead of specifying an actual device name, the keyword 'removable' can be used to limit the search
of acceptable live media to removable type only. Note that if you want to further restrict the media
to usb mass storage only, you can use the 'removable-usb' keyword.

{live-media-encryption|encryption}=TYPE
live-boot will mount the encrypted rootfs TYPE, asking the passphrase, useful to build paranoid live
systems :-). TYPE supported so far is "aes" for loop-aes encryption type.

live-media-offset=BYTES
This way you could tell live-boot that your image starts at offset BYTES in the above specified or
autodiscovered device, this could be useful to hide the live system ISO or image inside another ISO
or image, to create "clean" images.

live-media-path=PATH
Sets the path to the live filesystem on the medium. By default, it is set to '/live' and you should
not change that unless you have customized your media accordingly.

live-media-timeout=SECONDS
Set the timeout in seconds for the device specified by "live-media=" to become ready before giving
up.

module=NAME
Instead of using the default optional file "filesystem.module" (see below) another file could be
specified without the extension ".module"; it should be placed on "/live" directory of the live
medium.

netboot[=nfs|cifs]
This tells live-boot to perform a network mount. The parameter "nfsroot=" (with optional "nfsopts="),
should specify where is the location of the root filesystem. With no args, will try cifs first, and
if it fails nfs.

nfsopts=
This lets you specify custom nfs options.

nofastboot
This parameter disables the default disabling of filesystem checks in /etc/fstab. If you have static
filesystems on your harddisk and you want them to be checked at boot time, use this parameter,
otherwise they are skipped.

nopersistence
disables the "persistence" feature, useful if the bootloader (like syslinux) has been installed with
persistence enabled.

noeject
Do not prompt to eject the live medium.

ramdisk-size
This parameter defines a custom ramdisk size (it's the '-o size' option of tmpfs mount). By default,
there is no ramdisk size set, so the default of mount applies (currently 50% of available RAM). Note
that this option has currently no effect when booting with toram.

overlay-size=SIZE
The size of the tmpfs mount (used for the upperdir union root mount) in bytes, and rounded up to
entire pages. This option accepts a suffix % to limit the instance to that percentage of your
physical RAM or a suffix k, m or g for Ki, Mi, Gi (binary kilo (kibi), binary mega (mebi) and binary
giga (gibi)). By default, 50% of available RAM will be used.

swap=true
This parameter enables usage of local swap partitions.

persistence
live-boot will probe devices for persistence media. These can be partitions (with the correct GPT
name), filesystems (with the correct label) or image files (with the correct file name). Overlays are
labeled/named "persistence" (see persistence.conf(5)). Overlay image files are named "persistence".

persistence-encryption=TYPE1,TYPE2 ... TYPEn
This option determines which types of encryption that are allowed to be used when probing devices for
persistence media. If "none" is in the list, we allow unencrypted media; if "luks" is in the list, we
allow LUKS-encrypted media. Whenever a device containing encrypted media is probed the user will be
prompted for the passphrase. The default value is "none".

persistence-media={removable|removable-usb}
If you specify the keyword 'removable', live-boot will try to find persistence partitions on
removable media only. Note that if you want to further restrict the media to usb mass storage only,
you can use the 'removable-usb' keyword.

persistence-method=TYPE1,TYPE2 ... TYPEn
This option determines which types of persistence media we allow. If "overlay" is in the list, we
consider overlays (i.e. "live-rw" and "home-rw"). The default is "overlay".

persistence-path=PATH
live-boot will look for persistency files in the root directory of a partition, with this parameter,
the path can be configured so that you can have multiple directories on the same partition to store
persistency files.

persistence-read-only
Filesystem changes are not saved back to persistence media. In particular, overlays and netboot NFS
mounts are mounted read-only.

persistence-storage=TYPE1,TYPE2 ... TYPEn
This option determines which types of persistence storage to consider when probing for persistence
media. If "filesystem" is in the list, filesystems with matching labels will be used; if "file" is in
the list, all filesystems will be probed for archives and image files with matching filenames. The
default is "file,filesystem".

persistence-label=LABEL1,LABEL2 ... LABELn
live-boot will use the names in this list (instead of "persistence") when searching for persistent
storage. Each LABEL can be a valid filename, partition label, or GPT name. The default is
"persistence".

noeject
This option causes live-boot to reboot without attempting to eject the media and without asking the
user to remove the boot media.

showmounts
This parameter will make live-boot to show on "/" the ro filesystems (mostly compressed) on
"/lib/live". This is not enabled by default because could lead to problems by applications like
"mono" which store binary paths on installation.

silent
If you boot with the normal quiet parameter, live-boot hides most messages of its own. When adding
silent, it hides all.

todisk=DEVICE
Adding this parameter, live-boot will try to copy the entire read-only media to the specified device
before mounting the root filesystem. It probably needs a lot of free space. Subsequent boots should
then skip this step and just specify the "live-media=DEVICE" boot parameter with the same DEVICE used
this time.

toram
Adding this parameter, live-boot will try to copy the whole read-only media to the computer's RAM
before mounting the root filesystem. This could need a lot of ram, according to the space used by the
read-only media.

union=overlay|aufs
By default, live-boot uses overlay. With this parameter, you can switch to aufs.

FILES (old)

       /etc/live.conf
           Some variables can be configured via this config file (inside the live system).

       live/filesystem.module
           This    optional   file   (inside   the   live   media)   contains   a   list   of   white-space   or
           carriage-return-separated file names corresponding to disk images in the "/live" directory.  If  this
           file  exists,  only  images listed here will be merged into the root aufs, and they will be loaded in
           the order listed here. The first entry in this file will be the "lowest" point in the aufs,  and  the
           last file in this list will be on the "top" of the aufs, directly below /overlay.  Without this file,
           any images in the "/live" directory are loaded in alphanumeric order.

FILES

       /etc/live/boot.conf

       /etc/live/boot/*

       live/boot.conf

       live/boot/*

       persistence.conf

HOMEPAGE

       More information about  live-boot  and  the  Debian  Live  project  can  be  found  on  the  homepage  at
       <https://wiki.debian.org/DebianLive>  and  in  the  manual  at  <https://live-team.pages.debian.net/live-
       manual/>.

BUGS

       Bugs can be reported by submitting a bugreport for the live-boot package in the Bug  Tracking  System  at
       <http://bugs.debian.org/>   or   by  writing  a  mail  to  the  Debian  Live  mailing  list  at  <debian-
       live@lists.debian.org>.

AUTHOR

       live-boot was originally written by Daniel Baumann <mail@daniel-baumann.ch>. Since 2016  development  has
       been continued by the Debian Live team.