mkinitramfs [-c compress] [-d confdir] [-k] -o outfile [-r root] [-v] [version]
mkinitramfs [--supported-host-version= hversion]
mkinitramfs [--supported-target-version= tversion]
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.
Create an initramfs for current running kernel:
mkinitramfs -o ~/tmp/initramfs-$(uname -r)
Create an initramfs for specific kernel and keep builddirs:
mkinitramfs -k -o ~/tmp/initramfs-2.6.21-686 2.6.21-686
Debug initramfs creation (check out written logfile)
sh -x mkinitramfs -o ~/tmp/initramfs-$(uname -r) 2> ~/tmp/log
The initramfs-tools are written by Maximilian Attems <email@example.com>, Jeff Bailey <firstname.lastname@example.org> and numerous others.
initramfs.conf(5), initramfs-tools(8), update-initramfs(8), lsinitramfs(8).