Using Files to Modify a Global Configuration or the Scheduler

To change a global configuration, use the qconf –mconf command. To change the scheduler, use the qconf –msconf command.

Both of these commands open a temporary file in an editor. When you exit the editor, any changes that you save to this temporary file are processed by the system and take effect immediately. The editor used to open the temporary file is the editor specified by the EDITOR environment variable. If this variable is undefined, the vi editor is used by default.

You can use the EDITOR environment variable to automate the behavior of the qconf command. Change the value of this variable to point to an editor program that modifies a file whose name is given by the first argument. After the editor modifies the temporary file and exits, the system reads in the modifications, which take effect immediately.

If the modification time of the file does not change after the edit operation, the system sometimes incorrectly assumes that the file was not modified. Therefore you should insert a sleep 1 instruction before writing the file, to ensure a different modification time.

You can use this technique with any qconf –m... command. However, the technique is especially useful for administration of the scheduler and the global configuration, as you cannot automate the procedure in any other way.

Example 8–12 Modifying the Schedule Interval

The following example modifies the schedule interval of the scheduler:

#!/bin/ksh
# sched_int.sh: modify the schedule interval
# usage: sched_int.sh <n>, where <n> is
# the new interval, in seconds. n < 60

TMPFILE=/tmp/sched_int.$$
if [ $MOD_SGE_SCHED_INT ]; then
     grep -v schedule_interval $1 > $TMPFILE
     echo "schedule_interval 0:0:$MOD_SGE_SCHED_INT" >> $TMPFILE
# sleep to ensure modification time changes
     sleep 1
     mv $TMPFILE $1
else
     export EDITOR=$0
     export MOD_SGE_SCHED_INT=$1
     qconf -msconf
fi

This script modifies the EDITOR environment to point to itself. The script then calls the qconf –msconf command. This second nested invocation of the script modifies the temporary file specified by the first argument and then exits. The grid engine system automatically reads in the changes, and the first invocation of the script terminates.