If you're really looking to cover all bases, there's a little gotcha
in Solaris (even in 10) that will make this startup script fail if
it's invoked with sh (as most startup scripts that I've seen are).
The 'test -e' is unavailable in sh on Solaris. You need to use -r
(file exists and is readable) or -f (file exists and is a regular
file) or -s (file exists and has size > 0).
I was burned by this when I first started administering Solaris
machines, as I used to use "if [ -e" all of the time in my shell
scripting. Just one more "issue" that Solaris has, but that's a whole
different mailing list, right there.
-Rich Goodson
Sr. Unix Admin
Mediacom Communications
On Mar 26, 2009, at 1:02 AM, Doug Barton wrote:
dev_n...@zoho.com wrote:
If named is invoked successfully on startup, then the contents of
the
PID file will be overwritten with the new PID value.
If named *isn't* invoked successfully on startup, then that's a
separate
error condition that should be detected and dealt with, within the
whole
startup subsystem.
The problems with using "ps" to find the named process include:
-- you can get false matches if you don't tailor your string
matching
_just_right_,
-- unexpectedly "missed" matches if the command-line arguments
change,
even a little bit (e.g. if someone bypasses the wrapper script on an
emergency basis to start the process manually, with the arguments
given
perhaps in a different order), and
-- since "ps" operates on a constantly-changing data source, it can
"miss" legitimate processes in the process table. I've seen that
happen
many many times with "ps" on Solaris, not sure if Linux or other
flavors
of Unix have some sort of concurrency-control mechanism to prevent
that
phenomenon.
I agree all your opitions on ps's drawbacks.
what I said is, kill -0 $PID will return true even the process who
owns $PID isn't named.
for example, named.pid wasn't removed after a system shutdown, the
value in it is 1234.
after system startup, another process is launched and owns that
process id of 1234.
Boys boys boys .... there is no need to fight, you're both right. :)
NAMED_PID=/path/to/pid
if [ -e "$NAMED_PID" ]; then
if ps -p `cat $NAMED_PID` | grep named; then
# named is already running, do what's appropriate
else
# pid file is bogus, remove it and start named
unlink $NAMED_PID
<start named>
fi
else
if ps -U nobody | grep named; then
# named is running without a pid file, oops
<do something useful>
else
if ps -ax | grep [n]amed; then
# something is probably really wrong here
# probably want to stop and look first
else
<start named>
fi
fi
fi
I agree with Kevin that ps on Solaris has "issues," although I've
never had similar problems on FreeBSD I still prefer to try and cover
all the bases. Limiting the number of processes that you examine with
ps by looking only at those with user nobody helps limit your chances
of false positives, although it doesn't cover someone typing 'named'
as root.
Of course on FreeBSD the /etc/rc.d/named script already handles all of
this and much more for you. :)
Doug
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