Force a disk offline and power it down in Linux

rmdisk.sh

#!/bin/bash
 
# AUTHOR: Tommy Butler
#
# DESCRIPTION:
# Run this script to offline and delete a disk from your Linux system.  
# It should work for most people, but if you've got an old kernel it may not.
# Unless you know what you're doing, DO NOT USE THIS SCRIPT!
#
# LICENSE: Perl Artistic License - http://dev.perl.org/licenses/artistic.html
#
# DISCLAIMER AND LIMITATION OF WARRANTY:
# This software is distributed in the hope that it will be useful, but without 
# any warranty; without even the implied warranty of merchantability or fitness 
# for a particular purpose.  USE AT YOUR OWN RISK.  I ASSUME NO LIABILITY.
 
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
 
DISK=$1;
 
if [[ `id -u` -ne 0 ]];
then
   echo Run this script with root or sudo
   exit 1
fi
 
while true;
do
   [[ "$DISK" != "" ]] && break;
   read -p 'Enter the name of the disk you want to offline and delete: ' DISK
done
 
if [[ "$( expr substr $DISK 1 4 )" == '/dev' ]];
then
   DISK=$( expr substr $DISK 6 10 )
fi
 
if [[ ! -e /sys/block/$DISK ]];
then
   echo No entry for /dev/$DISK was not found in /sys/block/ - Cannot continue
   exit 1
fi
 
echo Are you sure you want to offline and delete /dev/${DISK}?
 
select yn in "Yes" "No"; do
   case $yn in
      Yes ) break;;
      No ) exit;;
   esac
done
 
echo offline > /sys/block/$DISK/device/state
 
echo 1 > /sys/block/$DISK/device/delete
 
echo DONE
 
exit;

hi
it worked perfectly.
is there any way to get the drive back online?
i tried to make the bus to rescan but the device didnt came back.
thanks!

the difference between offline and 1 > delete is that offline only makes the disk unavailable to the block subsystem, while the latter physically tells the drive to power down.

# find /sys/bus/scsi/devices/host*/target*|grep state
/sys/bus/scsi/devices/host2/target2:0:0/2:0:0:0/state
/sys/bus/scsi/devices/host2/target2:0:0/2:0:0:2/state
/sys/bus/scsi/devices/host2/target2:0:0/2:0:0:1/state

# cat /sys/bus/scsi/devices/host2/target2:0:0/2:0:0:1/state
offline

the drawback is that if offlined first, apparently the kernel remembers it is in the offline state, so it does not come back online after rescan, so you must online it like this:
the problem is that the magic word to return online is not "online", but "running"... so who wrote the code had some reason to not call it "online"

# echo online > /sys/bus/scsi/devices/host2/target2:0:0/2:0:0:1/state
-su: echo: write error: Invalid argument

# echo running > /sys/bus/scsi/devices/host2/target2:0:0/2:0:0:1/state
#

this seems to be useful when you really want just to make the disk temporarily unavailable but not power it down, so instead of deleting it, you would just offline/running