diff options
authorDenys Vlasenko <>2009-11-25 16:30:29 (GMT)
committerDenys Vlasenko <>2009-11-25 16:30:29 (GMT)
commitdb5fdd14200585f9bddfb30e28a711c2e3e2195e (patch)
parent6609c38a1a6e91ba6d640cb02339475106c7991d (diff)
Add FAQ entry about touching .config
Signed-off-by: Denys Vlasenko <>
1 files changed, 16 insertions, 1 deletions
diff --git a/FAQ.html b/FAQ.html
index 452aaa3..c5cf206 100644
--- a/FAQ.html
+++ b/FAQ.html
@@ -29,6 +29,7 @@ have additions to this FAQ document, we would love to add them,
<li><a href="#init">Busybox init isn't working!</a></li>
<li><a href="#sed">I can't configure busybox on my system.</a></li>
<li><a href="#job_control">Why do I keep getting "sh: can't access tty; job control turned off" errors? Why doesn't Control-C work within my shell?</a></li>
+<li><a href="#touch_config">sed "/CONFIG_FOO/s/.*/CONFIG_FOO=y/" -i .config; make; does not enable applet foo</a></li>
<h2>Misc. questions</h2>
@@ -42,7 +43,7 @@ have additions to this FAQ document, we would love to add them,
<li><a href="#design">What is the design of busybox?</a></li>
<li><a href="#source">How is the source code organized?</a>
- <li><a href="#source_applets">The applet directories.</a></li>
+ <li><a href="#source_applets">The applet directories</a></li>
<li><a href="#source_libbb">The busybox shared library (libbb)</a></li>
@@ -502,6 +503,20 @@ int main(int argc, char *argv)
<hr />
+<h2><a name="touch_config">sed "/CONFIG_FOO/s/.*/CONFIG_FOO=y/" -i .config; make; does not enable applet foo</a></h2>
+ In some common cases like "make allnoconfig", both .config and dependent
+ generated files are updated, making their mtimes very close. If you have
+ a build script which modifies .config immediately after this,
+ and then rebuilds the busybox, it may happen that .config's mtime will be
+ still close the the generated files' mtimes. If filesystem
+ time granularity is low (for example, 1 second), these mtimes may end up
+ being equal, and dependent files wouldn't be rebuilt. The work around
+ is to add "sleep 1" before sed.
+<hr />
<h1>Misc. questions</h1>
<hr />