Recently noticied that on my 486/100 box (not very slow --
it was very fast some years ago, but not for now) some startup
scripts are not executed (executed, but services not started).
After some investigations I found this:
$ /etc/rc.d/init.d/named start
Starting named:
$ _
But (^ markers are mine):
$ sh /etc/rc.d/init.d/named start
^^
Starting named: [ OK ]
^^^^^^
$ _
After some more investigations, I found the cause of the problem:
>From /etc/.../named, function daemon is called, that, before other
work, checks if process with given name already started. Relevant
lines from /etc/rc.d/init.d/functions (daemon) looks like (just an
example, not a real lines):
...
if [ -n "`pidof $proc`" ] ; then
exit 0
fi
..
And here is something like pstree for this:
1234 /etc/rc.d/init.d/named start -- main rc script; note it's name
1251 /etc/rc.d/init.d/named -- forked `pidof ...`; also note name
inside 1251, if I do "ps -C named", I get two pids,
namely 1234 and 1251; hence pidof returns those (actually
three, as there is another fork by sh)
If I execute that as "sh ...", 1234 process will be named "sh", not
"named", so pidof returns nothing.
So far, so good -- this is definitely a bug in initscripts.
But -- why this does not happen on faster machines!?
I have some more machines here, all at least Pentium/133
(and PII/500 and others), but with this, all is ok.
So the question is -- why on faster machine pidof returns nothing!?
Maybe it openes /proc for scan before it is "updated" to reflect
creation of new process, and even for top one?! Looks like it is
also a bug in kernel...
For completness: tried with all kernels shipped by redhat since
6.0 release (2.2.5..2.2.14), compiled for 386 or 486.
All of this gives me the same results on my 486 box -- most
of services won't start. Also tried many kernels on faster machines,
and even tried 386 versions on those -- all looks "good", i.e.
pidof (seemed) returns nothing.
Also very interesting point here is that when those scripts executed
by rc on startup, about 99% of services started. But when I start them
by hand, executing "/etc/.../service start" from command prompt,
100% of them are _not_ started. Only by prefixing by "sh ".
Any ideas?
Regards,
Michael.
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