mkinitramfs - low-level tool for generating an initramfs image

       The   initramfs-tools   are   written   by   Maximilian    Attems    <maks@debian.org>,    Jeff    Bailey
       <jbailey@raspberryginger.com> and numerous others.

       The  mkinitramfs  script  generates  an initramfs image.  The initramfs is a compressed cpio archive. The
       archive can be used on a different box of the same arch with the corresponding Linux kernel.  mkinitramfs
       is meant for advanced usage. On your local box  update-initramfs  calls  mkinitramfs  with  the  relevant
       parameters.  update-initramfs keeps sha1sum of generated initramfs. It takes care to generate backups and
       eventually runs the bootloader.

       At  boot  time,  the  kernel  unpacks that archive into RAM disk, mounts and uses it as initial root file
       system. All finding of the root device happens in this early userspace.

mkinitramfs honours the TMPDIR environment  variable.  If  set,  it  uses  subdirectories  in  the  given
       directory  to  create  its temporary working directories. Else it uses /var/tmp as default value for that
       purpose. The given directory should be on a filesystem which allows the execution of files stored  there,
       i.e.  should not be mounted with the noexec mount option.

       If SOURCE_DATE_EPOCH is set, mkinitramfs attempts to generate a reproducible initramfs image.

       Create an initramfs for current running kernel:

       mkinitramfs-o~/tmp/initramfs-$(uname-r)

       Create an initramfs for specific kernel and keep builddirs:

       mkinitramfs-k-o~/tmp/initramfs-2.6.21-6862.6.21-686

       Debug initramfs creation (check out written logfile)

       sh-xmkinitramfs-o~/tmp/initramfs-$(uname-r)2>~/tmp/log

/etc/initramfs-tools/initramfs.conf
              The  default  configuration  file  for  the script. See initramfs.conf(5) for a description of the
              available configuration parameter.

       /etc/initramfs-tools/modules
              Specified modules will be put in the generated image and loaded when the system boots. The  format
              - one per line - is identical to that of /etc/modules, which is described in modules(5).

       /etc/initramfs-tools/conf.d
              The  conf.d directory allows one to hardcode bootargs at initramfs build time via config snippets.
              This allows one to set ROOT or RESUME.  This is especially useful for bootloaders,  which  do  not
              pass an root bootarg.

       /etc/initramfs-tools/DSDT.aml
              If  this file exists, it will be appended to the initramfs in a way that causes it to be loaded by
              ACPI.

       mkinitramfs - low-level tool for generating an initramfs image

-ccompress
              Override the COMPRESS setting in initramfs.conf.

       -dconfdir
              Set an alternate configuration directory.

       -k     Keep the temporary directory used to make the image.

       -lcompresslevel
              Override the COMPRESSLEVEL setting in initramfs.conf.

       -mmodules
              Override the MODULES setting in initramfs.conf.

       -ooutfile
              Write the image to outfile.

       -rroot
              Override the ROOT setting in initramfs.conf.

       -v     Set the verbose mode output.

       version
              Set the kernel version of the initramfs image (defaults to the running kernel).

       --version
              Display version information and exit.

       -h, --help
              Display usage information and exit.

initramfs.conf(5), initramfs-tools(7), update-initramfs(8), lsinitramfs(8), unmkinitramfs(8).

initramfs-tools                                    2018/07/18                                     MKINITRAMFS(8)

mkinitramfs [option]...  -ooutfile [version]
       mkinitramfs--versionmkinitramfs-h