mke2fs: document the hash_seed option

For reproducible builds, it is necessary to control the random seed used
for hashing. Document the extended option for this feature.

Fixes: e1f71006 ("AOSP: mke2fs, libext2fs: make filesystem image reproducible")
Signed-off-by: Ralph Siemsen <ralph.siemsen@linaro.org>
Reviewed-by: Andreas Dilger <adilger@dilger.ca>
Message-ID: <20250910-mke2fs-small-fixes-v2-1-55c9842494e0@linaro.org>
Signed-off-by: Theodore Ts'o <tytso@mit.edu>

diff --git a/misc/mke2fs.8.in b/misc/mke2fs.8.in
index 13ddef47baa3936cf1f498e6fe35c2f6f658d80f..14bae326b446288e0799d9fe189583818392b520 100644 (file)
--- a/misc/mke2fs.8.in
+++ b/misc/mke2fs.8.in
@@ -320,6 +320,10 @@ In the default configuration, the
 .I strict
 flag is disabled.
 .TP
+.BI hash_seed= UUID
+Use the specified UUID as the seed for hashing, rather than generating a
+random seed each time. Intended for use with reproducible builds.
+.TP
 .B lazy_itable_init\fR[\fB= \fI<0 to disable, 1 to enable>\fR]
 If enabled and the uninit_bg feature is enabled, the inode table will
 not be fully initialized by

diff --git a/misc/mke2fs.c b/misc/mke2fs.c
index 7f81a5137501e0983c071778e898d732c98c2ac8..3a8ff5b1c3d943dfccb9542b818ab69e8df9dd37 100644 (file)
--- a/misc/mke2fs.c
+++ b/misc/mke2fs.c
@@ -1180,6 +1180,7 @@ static void parse_extended_opts(struct ext2_super_block *param,
                        "\trevision=<revision>\n"
                        "\tencoding=<encoding>\n"
                        "\tencoding_flags=<flags>\n"
+                       "\thash_seed=<UUID for hash seed>\n"
                        "\tquotatype=<quota type(s) to be enabled>\n"
                        "\tassume_storage_prezeroed=<0 to disable, 1 to enable>\n\n"),
                        badopt ? badopt : "");