[Git][reproducible-builds/reproducible-website][master] docs: document reproducible XFS filesystems

[Chris Lamb (@lamby)]

Chris Lamb pushed to branch master at Reproducible Builds / reproducible-website


Commits:
2cf0f4c8 by Luca Di Maio at 2025-12-15T18:04:37+01:00
docs: document reproducible XFS filesystems

As of the upcoming 6.18.0 release it will be possible to create
reproducible XFS system images. Adding them to the docs.

Signed-off-by: Luca Di Maio <luca.dimaio1 at gmail.com>

- - - - -


1 changed file:

- _docs/system_images.md


Changes:

=====================================
_docs/system_images.md
=====================================
@@ -44,6 +44,39 @@ It is also possible to produce bit-reproducible filesystems with recent mkfs.ext
     tar --sort=name --mtime=@$SOURCE_DATE_EPOCH --clamp-mtime --pax-option=exthdr.name=%d/PaxHeaders/%f,delete=atime,delete=ctime -cf /tmp/root.tar -C $rootdir .
     mkfs.ext2 -F -d /tmp/root.tar -E hash_seed=035cb65d-0a86-404a-bad7-19c88d05e400 -U 12341234-a4ec-4304-a70f-c549ea829da9 -L root $rootdev
 
+XFS
+===
+
+Recent versions of `mkfs.xfs` from xfsprogs support creating bit-reproducible XFS filesystems through
+environment variables and direct directory population capabilities.
+
+The reproducible build support was introduced through two key features:
+
+**Environment Variables for Deterministic Behavior:**
+
+* `SOURCE_DATE_EPOCH`: When set, all filesystem timestamps use this value instead of the current time.
+* `DETERMINISTIC_SEED=1`: When set, uses a fixed seed value for random number generation instead of reading from `/dev/urandom`.
+
+**Directory Population:**
+
+The `-p file=/path/to/directory` option allows populating a newly created XFS filesystem directly from
+an existing directory structure, without needing to mount the filesystem.
+
+    export SOURCE_DATE_EPOCH=1234567890 \
+    export DETERMINISTIC_SEED=1 \
+    mkfs.xfs \
+        -m uuid=12341234-a4ec-4304-a70f-c549ea829da9 \
+        -L my-label \
+        -p file=/path/to/rootfs \
+        disk.img
+
+**Important Notes:**
+
+* The UUID should be explicitly set with `-m uuid=` to ensure reproducibility
+* The filesystem label shold be explicitly set with `-L` option
+
+`xfsprogs` version 6.18.0 and higher is needed for this to work.
+
 ISO filesystem
 ==============
 



View it on GitLab: https://salsa.debian.org/reproducible-builds/reproducible-website/-/commit/2cf0f4c8dd6464f0ea2a22ed2508f98922758889

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