casper man page on ElementaryOS

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CASPER(7)		     Initramfs-tools hook		     CASPER(7)

       casper - a hook for initramfs-tools to boot live systems.

       BOOT=casper As kernel parameter boot prompt.

       Casper  is  a  hook  for	 initramfs-tools used to generate an initramfs
       capable to boot live  systems  as  those	 created  by  make-live.  This
       includes	 the  Debian-Live isos, netboot tarballs, and usb stick images
       and Ubuntu live cds. At boot time it will look for a (read-only)	 media
       containing a "/casper" directory where a root filesystems (often a com‐
       pressed squashfs) is stored. If found, it will create a writable	 envi‐
       ronment, using unionfs, for debian like systems to boot from.

	      This enables a special "serial" login shell (experimental).

	      uses  xdebconfigurator, if present on the rootfs, to configure X
	      instead of the standard procedure (experimental).

       hostname=HOSTNAME , userfullname=USERFULLNAME , username=USERNAME
	      Those parameters lets you override values read from  the	config

       {keyb|kbd-chooser/method}=KEYBOARD   ,	{klayout|console-setup/layout‐
       code}=LAYOUT    ,    {kvariant|console-setup/variantcode}=VARIANT     ,
       {kmodel|console-setup/modelcode}=CODE ,	koptions=OPTIONS
	      Configure	 the running keyboard as specified, if this one misses
	      casper behaves as if "keyb=us" was specified. It will be	inter‐
	      fered  from  "locale=" if locale is only 2 lowecase letters as a
	      special case. You could also specify  console  layout,  variant,
	      code, and options (no defaults).

	      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).

	      If  this variable is set, dhcp and static configuration are just
	      skipped and the system will use the (must	 be)  media-preconfig‐
	      ured /etc/network/interfaces instead.

	      If  you  specify	one  of this two equivalent forms, casper will
	      first try to find this device for the "/casper" directory	 where
	      the  read-only root filesystem should reside. If it did not find
	      something usable, the normal scan	 for  block  devices  is  per‐

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

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

       locale=LOCALE | debian-installer/locale=LOCALE
	      Configure the running locale as specified, if  not  present  the
	      live-media  rootfs  configured  locale  will be used and if also
	      this one misses casper behave as "locale=en_US.UTF-8" was speci‐
	      fied.  If only 2 lowercase letter are specified (like "it"), the
	      "maybe wanted" locale is generated (like it:IT.UTF-8),  in  this
	      case  if	also "keyb=" is unspecified is set with those 2 lower‐
	      case letters (keyb=it).

	      This tells casper 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.

	      Casper will look for persistent and snapshot partitions or files
	      labeled "casper-rw", "home-rw", and files	 called	 "casper-sn*",
	      "home-sn*"  and  will try to, in order: mount as /cow the first,
	      mount the second in /home, and just copy	the  contents  of  the
	      latter  in  appropriate locations (snapshots). Snapshots will be
	      tried to be updated on  reboot/shutdown.	Look  at  casper-snap‐
	      shot(1) for more informations.

	      disables the above mentioned "persistent" feature, useful if the
	      bootloader (like syslinux) has been  installed  with  persistent

	      Casper  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.

	      This parameter will make casper to show on "/" the  ro  filesys‐
	      tems  (mostly  compressed)  on  /casper.	This is not enabled by
	      default because could lead  to  problems	by  applications  like
	      "mono" which store binary paths on installation.

	      Start  up	 to  text-mode	shell prompts, disabling the graphical
	      user interface.

	      Adding this parameter, casper 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

       toram  Adding  this  parameter, casper 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.

	      A path to a file present on the rootfs could be used to  preseed
	      debconf database.

	      Bring up the network while running preseed/early_command.

	      All  debian  installed packages could be preseeded from command-
	      line that way, beware of blanks spaces, they will interfere with
	      parsing, use a preseed file in this case.

	      Check  that  the	discovered medium matches UUID rather than the
	      default UUID embedded in the initramfs.

	      Do not check that any UUID embedded in the initramfs matches the
	      discovered  medium.   casper  may	 be told to generate a UUID by
	      setting CASPER_GENERATE_UUID=1 when building the initramfs.

	      Do not prompt to eject the CD on reboot.

       /etc/casper.conf some variables can be configured via this config file.

       casper works fully on amd64, i386 and ppc, it should also run on	 other

       Debian Live project <>


       casper was written by Tollef Fog Heen <>, Matt Zim‐
       merman	    <>,       and	  Marco	       Amadori

       This	manual	   page	    was	    written	by    Marco    Amadori
	      for the Debian project (but may be used by others).

1.69			       Thu,  28 Sep 2006		     CASPER(7)

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