Automating recurring tasks with Cron

Setup a crontab file which defines whe the task should run:

m h d M D /script


m minute: 0-59
h hour: 0-23
d day of the month: 1-31
M month of the year: 1-12
D day of the week, Sunday-0, 0-6
/script the script to execute

Values that are not relevant can be replaced with a ‘*” character.


Run scriptA at 1:00 am:

* 1 * * * /scriptA

Run scriptB at every 15 minutes past the hour:

15 * * * * /scriptB

Run scriptC on the hour and every 30 minutes past the hour:

0,30 * * * * /scriptC

Run scriptD at 10,11 and 12, every Monday:

* 10-12 * * 1 /scriptC

To install the crontab setings, run:

crontab filename

To list the current crontab settings:

crontab -l

Common Linux Commands

df shows free and used disk space
top shows memory usage – updates in real time
ps Process Status – lists running processes
ps -ef show system processes
find . -name FILENAME -print locate a file named FILENAME and show it’s location
grep -r “pattern” * search through all files and subdirectories from the current directory for the given pattern and print matches
uname -a displays the current kernel version
lsb_release -a displays Ubuntu installation version
fdisk -l lists partition info

Ubuntu/Debian Package Management

Install an app: sudo apt-get install name

Remove: sudo apt-get remove name (‘apt-get remove –purge name’ to remove all config files also)

List installed packages: sudo dpkg –list | more

RPM Commands (Red Hat/Fedora and derivatives)

rpm -ivh PACKAGE installs a new RPM
rpm -e PACKAGE uninstalls an RPM
rpm -qi PACKAGE Queries that a package is unstalled and displays information about it

IBM and BEA join together to submit JSR for cross App Server tools

As part of the Java Tools Community initiative announced in the news yesterday, IBM and BEA Systems have announced they have created 3 Java Specification Requests (JSRs) for 3 new technologies which will be developed using the Java Community Process (JCP) and will be implemented on both IBM Websphere as well as BEA Weblogic.

The 3 new specifications are:

  • Service Data Objects: will provide a common mechanism to pull data from multiple sources such as XML sources and databases
  • Timer for Application Servers, a mechanism for scheduling processing jobs
  • Work Manager for Application Servers, for setting up processing tasks in parallel

Industry analysts have commented that the omission of Sun in the group developing these new specifications is significant, and probably signifies the beginning end of Sun’s involvement in the development of new technologies based on Java technology. IBM and BEA are the dominant market players in the Application Server market space, and with this announcement are now together shaping new future technologies on the Java platform.