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update-initrd(8)            System Manager's Manual           update-initrd(8)

       update-initrd  - (re-)generate initialization ramdisk for use with dis-

       update-initrd kernel-version

       update-initrd is used to generate an initialization ramdisk image (ini-
       trd  for  short) for use with the discover(8) utility, to perform boot-
       time hardware detection.  When a boot loader capable of loading an ini-
       trd  as  well  as a kernel image is used, device drivers used to access
       the root filesystem may be built as modules and placed  in  the  initrd
       instead  of compiled into the kernel itself.  update-initrd handles the
       creation of just such an initrd, using the currently installed  modules
       corresponding to kernel-version.

       Note  that  the  filesystem driver for the initrd filesystem (currently
       ext2) cannot be thus modularized, because the booting kernel  needs  to
       be able to comprehend the initrd.

       update-initrd  takes  a  single  argument  -  the version number of the
       (installed) kernel for which to generate an initrd image.

       update-initrd expects to find the following files, corresponding to  an
       installed Linux kernel-image package, for the Debian GNU/Linux system:


       A  check  for  actual  kernel  modules in the modules directory is also

       The only kernel versions currently supported by update-initrd  are  the
       2.2  series  and the 2.4 series; if some other kernel version is speci-
       fied, a warning is issued and the program exits without doing  anything

       Next,  a  temporary directory is created (see ENVIRONMENT below); if it
       cannot be, update-initrd exits with an error.  This temporary directory
       is used to create the initrd with mke2fs(8), and then mounted as a loop
       device (thus, the environment in which update-initrd is  run  needs  to
       support the loop device type).

       The  initrd  is populated with a linuxrc file, found in /usr/share/dis-
       cover/linuxrc, the ash(1) shell  (installed  as  "/bin/sh"),  mount(8),
       umount(8),  discover(8),  insmod(8), and modprobe(8).  The C and C math
       libraries are also installed, as is the discover  library  and  several
       data  files  used  by discover to identify hardware.  Some other essen-
       tials for an (extremely) minimal root filesystem are also prepared.

       Finally, the modules.dep file and any modules present  in  the  kernel-
       version  module  directory  identified  as SCSI drivers by discover, as
       well as the "sd_mod" (SCSI disk layer) and "ide-scsi"  (SCSI  emulation
       layer  for  IDE CD-ROM drives) modules, and any modules they depend on,
       are installed into the initrd.

       The initrd loop filesystem is then unmounted, compressed, and placed in
       /boot/initrd-kernel-version.gz;  any  existing  file  of  this  name is
       backed up to /boot/initrd-kernel-version.gz.old.

       TMPDIR If defined, update-initrd uses the contents of this variable  as
              the  parent of its temporary work directory.  Otherwise, /tmp is

       It would be nice to be able to arbitrarily specify the  modules  placed
       on  the  initrd,  and to use any filesystem type desired for the initrd
       (in which case it would be a good idea to check for  the  corresponding
       kernel module and error out).

       discover(8), discover.conf(5).

       Ian  Murdock  and  Branden Robinson for Progeny Linux Systems, Inc. and
       Debian GNU/Linux.

                                  2001-10-15                  update-initrd(8)