squashfs · shipping · also Squashfs

SquashFS

SquashFS is a Linux read-only filesystem for compact images, supporting compression of file data, inodes and directories.

Related Observatory article: SquashFS on hesela.com

mksquashfs creates populated images. Fragment blocks can pack file tails; inode and directory metadata are packed separately. Metadata blocks may remain uncompressed when requested or when compression would enlarge them. [1]

A read-only filesystem is not a cryptographic trust decision. For a block-backed image, dm-verity can check accessed blocks against a trusted root hash; successful decompression alone does not authenticate the image. [2]

Relations

related
EROFS, Read-only mount, dm-verity, Transparent filesystem compression

Advantages

  • Compressed data, packed metadata and fragments support space-conscious read-only image layouts. [1]

Limitations

  • The reader must support the image features and compressor; compact layout alone does not establish faster reads. [1]

Citations

  1. Linux v6.16: Squashfs 4.0, image creation, metadata and fragment design (accessed 2026-10-23)
  2. Linux v6.16: dm-verity trust and on-demand verification (accessed 2026-10-23)
Sources & caveats
  • Version-pinned documentation review; no image-mount experiment or comparative benchmark.

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Hesela team. SquashFS. Hesela. 2026-10-23. https://hesela.dev/terms/squashfs/