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README hasn't been updated since the initial checkin in 2005, and the old contents are obsolete: the original goals have either been achieved or abandoned (we're not going to build udev against klibc), and initrds are largely forgotten. Replace these with a quick summary of what an initramfs is needed for, how initramfs-tools does it, and a pointer to the manual pages. Suggested-by: Robie Basak <robie.basak@ubuntu.com> Signed-off-by: Ben Hutchings <ben@decadent.org.uk>
38 lines
1.7 KiB
Plaintext
38 lines
1.7 KiB
Plaintext
initramfs-tools
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===============
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The Linux kernel may boot using an "initramfs", an archive of files
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that it unpacks into an in-memory file system at the beginning of the
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boot process. This archive must contain its own init program which
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the kernel will run as the first user process. In a Debian system,
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the initramfs is responsible for:
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* Loading essential driver modules
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* Setting up a network connection, if required
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* Setting up layered storage devices, if required
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* Resuming from hibernation (suspend-to-disk), if possible
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* Checking and mounting the root and /usr file systems
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* Handing over to the main init system
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initramfs-tools is designed to be extensible, and many other packages
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provide these and additional features in the initramfs.
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On x86 systems, the initramfs can also contain CPU microcode updates
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that the kernel will apply at a very early stage. These are provided
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by the (non-free) intel-microcode and amd64-microcode packages.
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Debian's official kernel packages require the use of an initramfs,
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since drivers and filesystem code are built as modules that need to be
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loaded before the file systems can be mounted. Custom kernel packages
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that have this code built-in may still need an initramfs to set up
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layered storage devices or to provide microcode updates.
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If initramfs-tools is installed, it will generate an initramfs
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automatically whenever a kernel is installed or upgraded (and remove
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it when the kernel is removed). If only initramfs-tools-core is
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installed, you can run mkinitramfs to generate an initramfs.
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The initramfs-tools(7) manual page documents the supported parameters
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and how to extend initramfs-tools. There are additional manual pages
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for the various commands and configuration files.
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