Unit objectives. IBM Power Systems

Transcription

1 Unit 8 Scheduling Course merials may not be reproduced in whole or in part without the prior written permission of IBM. 5.2

2 Unit objectives After completing this unit, you should be able to: Understand the role of the cron daemon Use crontab files to schedule jobs on a periodic basis Use the command to schedule a job or series of jobs some time in the future Use the bch command to schedule jobs in a queue to allevie immedie system demand

3 The cron daemon Responsible for running scheduled jobs Starts: crontab command events (regularly scheduled jobs) command events (one time only execution specified time) bch command events (run when CPU load is low)

4 crontab files Used to start regularly occurring jobs Schedule is defined in: /var/spool/cron/crontabs/$user Files to control crontab privileges of users: /var/adm/cron/cron.deny lists users who cannot use crontab /var/adm/cron/cron.allow lists users who can use crontab An empty cron.deny exists by default.

5 Form of a crontab file Form of entries: minute hour de-of-month month day-of-week command To view current crontab: crontab -l * * * /usr/sbin/skulker * * 0 /usr/lib/spell/compress * * * ulimit ulimit 5000; 5000; /usr/lib/smdemon.cleanu > /dev/null /dev/null * * * /usr/bin/errclear -d -d S,O S,O * * * /usr/bin/errclear -d -d H * * * /usr/lib/ras/dumpcheck >/dev/null >/dev/null 2>&1 2>&1 0,30,45 0,30,45 * * * * /usr/sbin/dumpctrl -k -k >/dev/null >/dev/null 2>/dev/null 2>/dev/null......

6 Editing a crontab file One way to edit a crontab file: crontab -e -e A safer method: crontab -l -l > /tmp/crontmp vi vi /tmp/crontmp crontab /tmp/crontmp

7 The and bch commands The command submits a uniquely occurring job to be run by cron a specified time. 5 5 pm pm Friday Friday banner banner hello hello > > /dev/pts/0 /dev/pts/0 <ctrl-d> <ctrl-d> job job user.time.a user.time.a will will be be run run de de for for hosts hosts in in lpar50 lpar50 lpar51 lpar51 lpar52 lpar52 do do rsh rsh $host $host "echo "echo '<<EOF '<<EOF nohup nohup shutdown shutdown -Fr' -Fr' now now " " done done The bch command submits a job to be run when the processor load is sufficiently low. bch bch banner banner hello hello world world > > /dev/pts/0 /dev/pts/0 <ctrl-d> <ctrl-d>

8 Controlling jobs To list jobs: -l [user] q [user] l l root a root a 10:09:29 10:09:29 root a root a 10:19:53 10:19:53 test a test a 10:31:03 10:31:03 To cancel an job: -r job rm [job user] -r -r test a test a file: file: test a test a deleted deleted To cancel all your jobs: rm -

9 Documenting scheduling Have a copy of each user's crontab file Have a copy of the /etc/inittab file Scheduling Records

10 Unit summary Having completed this unit, you should be able to: Understand the role of the cron daemon Use crontab files to schedule jobs on a periodic basis Use the command to schedule a job or series of jobs some time in the future Use the bch command to schedule jobs in a queue to allevie immedie system demand