From: Gang Yan Date: Fri, 17 Oct 2025 02:12:09 +0000 (+0800) Subject: kbuild: doc: improve KBUILD_BUILD_TIMESTAMP documentation X-Git-Tag: v6.19-rc1~174^2~11 X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=bfb046f67ae1f20572d4dee73a173c6db706f5d4;p=thirdparty%2Fkernel%2Flinux.git kbuild: doc: improve KBUILD_BUILD_TIMESTAMP documentation This patch adds an example of how to set KBUILD_BUILD_TIMESTAMP to a specific date. Also, note that the provided timestamp is used for initramfs mtime fields, which are 32-bit and thus limited to dates between the Unix epoch and 2106-02-07 06:28:15 UTC. Dates outside this range will cause errors. Suggested-by: David Disseldorp Signed-off-by: Gang Yan Reviewed-by: David Disseldorp Reviewed-by: Nicolas Schier Link: https://patch.msgid.link/20251017021209.6586-1-gang.yan@linux.dev Signed-off-by: Nicolas Schier --- diff --git a/Documentation/kbuild/kbuild.rst b/Documentation/kbuild/kbuild.rst index 3388a10f2dcc8..82826b0332df4 100644 --- a/Documentation/kbuild/kbuild.rst +++ b/Documentation/kbuild/kbuild.rst @@ -328,8 +328,14 @@ KBUILD_BUILD_TIMESTAMP ---------------------- Setting this to a date string overrides the timestamp used in the UTS_VERSION definition (uname -v in the running kernel). The value has to -be a string that can be passed to date -d. The default value -is the output of the date command at one point during build. +be a string that can be passed to date -d. E.g.:: + + $ KBUILD_BUILD_TIMESTAMP="Mon Oct 13 00:00:00 UTC 2025" make + +The default value is the output of the date command at one point during +build. If provided, this timestamp will also be used for mtime fields +within any initramfs archive. Initramfs mtimes are 32-bit, so dates before +the 1970 Unix epoch, or after 2106-02-07 06:28:15 UTC will fail. KBUILD_BUILD_USER, KBUILD_BUILD_HOST ------------------------------------