06-15-2005
Quote:
Originally Posted by bakunin
While agreeing with the rest of your post on this (minor) issue I'd like to disagree: that depends on the system you're running on. AIX, for instance, has cron started in /etc/inittab with the "respawn" option and hence there is no need to start more than one cron processes. In my career as AIX administrator I have never seen mor than one cron process active (or any number of cron instances save 1, for that matter).
How often have you looked for multiple cron processes? Would you notice a second cron if you simply ran a "ps -ef" but were looking for something else? I can't speak to AIX since I've never worked on it. But on other systems, cron runs programs by forking itself, fiddling with the environment, and then exec'ing the program to be run. After the fork, and prior to the exec you have a 2nd process named cron. Most people tend to not schedule jobs to be run at, say, exactly at 4 minutes after midnight. Instead everyone and his brother will tend to schedule stuff,say, exactly at midnight. At these busy points, you can have dozens of cron processes waiting to exec. I have often seen several cron processes on both HP-UX and Solaris. In addition, we have a monitoring system called Big Brother that used to check for for exactly one copy of cron running. I got dragged out of bed at 2 in the morning because cron forked and Big Bro freaked. Big Bro has now been corrected.
Also I do not really approve of running "ps -ef" and looking for processing by name. Users can write their own programs and they can call one of their own programs "cron". We just had a case where a developer wrote a program to be invoked from cron. And yes, he called the program to be invoked: cron. In the case of pgrep, "pgrep -u root -x cron" would at least avoid that, but the forking problem remains.
10 More Discussions You Might Find Interesting
1. Shell Programming and Scripting
I'm puzzled by this one. I hope you can explain it to me.
I have a ksh shell script that gzips a file among other things. This works perfectly fine when the script is manually run through a shell. However, when the same script is run through cron, it does everything correctly, but it will... (2 Replies)
Discussion started by: hbau419
2 Replies
2. Shell Programming and Scripting
Hi,
Is there a way to determine if a Script is called from a
CRON job or from a commandline
Gerry. (2 Replies)
Discussion started by: jerryMcguire
2 Replies
3. Shell Programming and Scripting
Hello,
I have the following script which works fine when ran from the command line:
#!/apps/python/2.3.4/bin/python
import os
import sys
import time
user = os.getenv("USER")
string = time.strftime("%m%d%y0000 " + user, time.gmtime())
However, when I have this run by crontab, I... (4 Replies)
Discussion started by: cooldude
4 Replies
4. Shell Programming and Scripting
Hi,
I'm trying to execute a job on the last day of every month, for which i'm using the following code in my Korn shell script :
if ];
then
echo allowed only on last day of month. Today is `date +%d` >t.stm
echo Tomorrow is `date +%d -d tomorrow` >s.stm
exit 0
fi
...
....... (7 Replies)
Discussion started by: devilsadvocate
7 Replies
5. Linux
Hi,
When I googled, I came to know that I can not call the command
"service <service-name> start" from cron, insted I have to specify path to the service-name.
I wanted to know the reason.
Thanks,
Hansini (3 Replies)
Discussion started by: hansini
3 Replies
6. UNIX for Dummies Questions & Answers
Hi All,
I am calling a series of shell scripts via CRON so everything is running as root. However, in my error log file I am seeing the following errors. Please can anyone offer any advise as to the possible causes and solution to prevent the errors from appearing.
The Error 1227 seems to... (2 Replies)
Discussion started by: daveu7
2 Replies
7. Shell Programming and Scripting
Hi,
My shell script not getting called through cron job.
The same works fine when executed manually.
I tried to generate logs to find if the scripts has some errors related to path using following command- trying to execute .sh file every 5 mins:
*/5 * * * * /home/myfolder/abc.sh... (17 Replies)
Discussion started by: Dejavu20
17 Replies
8. Shell Programming and Scripting
I am using blow script :--
#!/bin/bash
FIND=$(ps -elf | grep "snmp_trap.sh" | grep -v grep) #check snmp_trap.sh is running or not
if
then
# echo "process found"
exit 0;
else
echo "process not found"
exec /home/Ketan_r /snmp_trap.sh 2>&1 & disown -h ... (1 Reply)
Discussion started by: ketanraut
1 Replies
9. Shell Programming and Scripting
Hi,
I am trying to capture logs of the script in the file as well as on the screen. I have used exec and tee command for this. While using exec command I am getting the correct output in the file but, script output is not getting displayed on the screen as it get executed.
Below is my sample... (14 Replies)
Discussion started by: Prathmesh
14 Replies
10. Shell Programming and Scripting
Hi, I've got a Bash backup script I'm trying to run on a directory via a cron job nightly. If I ssh in and run the script manually it works flawlessly. If I set up the cron to run evertything is totally messed up I don't even know where to begin.
Basically the path structure is
... (6 Replies)
Discussion started by: wyclef
6 Replies
LEARN ABOUT DEBIAN
cron-apt
CRON-APT(8) System Manager's Manual CRON-APT(8)
NAME
cron-apt -- program to update the system using apt-get
SYNOPSIS
cron-apt [configfile]
DESCRIPTION
This manual page documents briefly the cron-apt command.
cron-apt is a program that uses the information in /etc/cron-apt/action.d/ as arguments to apt-get line by line in file order.
OPTIONS
These programs follow the usual GNU command line syntax, with long options starting with two dashes (`-'). A summary of options is
included below. For a complete description, see the Info files.
--help
Show summary of options.
CONFIGURATION
Configuration can be done by editing /etc/cron-apt/config and by adding rules to /etc/cron-apt/action.d/ The variables that you can set in
/etc/cron-apt/config is documented in the configuration example in /usr/share/doc/cron-apt/examples/config
From version 0.5.0 the optional FILTERCTRLM attribute is deprecated.
SEE ALSO
apt-get (1)
aptitude (1)
AUTHOR
This manual page was written by Ola Lundqvist ola@inguza.com for the Debian GNU/Linux system (but may be used by others). This manual is
free software; you can redistribute it and/or modify it under the terms of the GNU General Public License as published by the Free Software
Foundation; either version 2 of the License, or (at your option) any later version.
CRON-APT(8)