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feat(cpio): add newc archive creation utility
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dracut-cpio is a minimal cpio archive creation utility written in Rust.
It provides support for a minimal set of features needed to create
performant and space-efficient initramfs archives:
- "newc" archive format only
- reproducible; inode numbers, uid/gid and mtime can be explicitly set
- data segment copy-on-write reflinks
  + using Rust io::copy()'s native copy_file_range() support[1]
  + optional archive data segment alignment for optimal reflink use[2]
- hardlink support
- comprehensive tests asserting GNU cpio binary output compatibility

1. Rust io::copy() copy_file_range()
   rust-lang/rust#75272

2. Data segment alignment
   We're bending the newc spec a bit to inject zeros after the file path
   to provide data segment alignment. These zeros are accounted for in
   the namesize, but some applications may only expect a single
   zero-terminator (and 4 byte alignment). GNU cpio and Linux initramfs
   handle this fine as long as PATH_MAX isn't exceeded.

Signed-off-by: David Disseldorp <ddiss@suse.de>
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ddiss authored and haraldh committed Nov 24, 2021
1 parent 94fc502 commit a9c6704
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12 changes: 12 additions & 0 deletions src/dracut-cpio/Cargo.lock

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11 changes: 11 additions & 0 deletions src/dracut-cpio/Cargo.toml
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[package]
name = "dracut-cpio"
description = "cpio archive generator for Dracut"
authors = ["David Disseldorp"]
license = "GPL-2.0"
version = "0.1.0"
edition = "2018"

[dependencies]
crosvm = { path = "third_party/crosvm" }
# please avoid adding any more dependencies
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