readahead initscript

readahead

#!/bin/bash
#
# readahead     set readhead for specific block devices
#
# chkconfig: 35 85 15
# description: set readhead for specific block devices
# processname: 
#
### BEGIN INIT INFO
# Provides: readahead
# Short-Description: set readahead for specific block devices
# Description: Use blockdev utility to set readahead for specific block devices
### END INIT INFO

# Source function library.
. /etc/rc.d/init.d/functions


# Path to the blockdev binary.
binary=/sbin/blockdev
RETVAL=0


# initialize dev_list array
dev_list=() 
# append devices below with format:
#   dev_list+=("/path/to/device|readahead_val")
dev_list+=("/dev/vdb|32")
dev_list+=("/dev/dm-2|32")


start() {
    for dev in "${dev_list[@]}"
    do
        device=${dev%%|*}
        devicename=${device##*/}
        value=${dev##*|}
        store_file="/var/run/readahead-${devicename}.default"

        # if readahead is already set to preferred value, 
        # skip to next iteration iteration
        current_value=$(${binary} --getra ${device})
        if [ ${current_value} = ${value} ]; then 
            echo "preferred readahead already set ${device}:${value}" 
            continue
        fi
        
        # store the current readahead value
        cmd="${binary} --getra ${device} > $store_file"
        action "storing current readahead value for ${device}:" eval "${cmd}"
        RETVAL=$?
        
        # if we couldnt store the current value, skip to next iteration
        if [ $RETVAL != 0 ]; then
           continue
        fi
        
        # set new the preferred readahead
        cmd="${binary} --setra ${value} ${device}"
        action "setting readahead for ${device} to ${value}:" eval "${cmd}"
        RETVAL=$?
        if [ $RETVAL = 0 ]; then 
           logger -t readahead "set readahead for ${device} to ${value}"
        fi
    done
}


stop() {
    for dev in "${dev_list[@]}"
    do
        device=${dev%%|*}
        devicename=${device##*/}
        store_file="/var/run/readahead-${devicename}.default"
        
        # if we can open $store_file, continue
        if [ -f ${store_file} ]; then
            value=$(cat $store_file)
            cmd="${binary} --setra ${value} ${device}"
            action "restoring default readahead value for ${device}:" eval "${cmd}"
            RETVAL=$?
            if [ $RETVAL = 0 ]; then
                logger -t 'readahead' "set readahead for ${device} to ${value}"
                rm -f ${store_file}
            fi
        else
            echo "could not open ${store_file}, unable to restore default value."
        fi
    done
}



status() {
    for dev in "${dev_list[@]}"
    do
	device=${dev%%|*}
	devicename=${device##*/}
	cmd="${binary} --getra ${device}"
	echo "current readahead value for ${device}: " $(eval "${cmd}")
    done
}



# See how we were called.
case "$1" in
  start)
	start
	;;
  stop)
	stop
	;;
  status)
        status
	;;
  *)
	echo $"Usage: $prog {start|stop|status|help}"
	RETVAL=2
esac

exit $RETVAL