Script for rescanning new (virtual) disk in Linux

I ran into a problem that I wanted to add a new virtual disk to a Linux virtual machine without rebooting the virtual machine. I Googled around and found this scripted from Kurt Garloff.

I tested the scripted and I got the new SCSI disk without rebooting.

Just to make sure that I always have access to the scripted I post it in this blog.

#!/bin/bash
# Skript to rescan SCSI bus, using the
# scsi add-single-device mechanism
# (w) 1998-03-19 Kurt Garloff (c) GNU GPL
# (w) 2003-07-16 Kurt Garloff (c) GNU GPL
# $Id: rescan-scsi-bus.sh,v 1.15 2004/05/08 14:47:13 garloff Exp $

setcolor ()
{
red=”e[0;31m”
green=”e[0;32m”
yellow=”e[0;33m”
norm=”e[0;0m”
}

unsetcolor ()
{
red=””; green=””
yellow=””; norm=””
}

# Return hosts. sysfs must be mounted
findhosts_26 ()
{
hosts=
if ! ls /sys/class/scsi_host/host* >/dev/null 2>&1; then
echo “No SCSI host adapters found in sysfs”
exit 1;
#hosts=” 0″
#return
fi
for hostdir in /sys/class/scsi_host/host*; do
hostno=${hostdir#/sys/class/scsi_host/host}
hostname=`cat $hostdir/proc_name`
hosts=”$hosts $hostno”
echo “Host adapter $hostno ($hostname) found.”
done
}

# Return hosts. /proc/scsi/HOSTADAPTER/? must exist
findhosts ()
{
hosts=
for driverdir in /proc/scsi/*; do
driver=${driverdir#/proc/scsi/}
if test $driver = scsi -o $driver = sg -o $driver = dummy -o $driver = device_info; then continue; fi
for hostdir in $driverdir/*; do
name=${hostdir#/proc/scsi/*/}
if test $name = add_map -o $name = map -o $name = mod_parm; then continue; fi
num=$name
driverinfo=$driver
if test -r $hostdir/status; then
num=$(printf ‘%dn’ `sed -n ‘s/SCSI host number://p’ $hostdir/status`)
driverinfo=”$driver:$name”
fi
hosts=”$hosts $num”
echo “Host adapter $num ($driverinfo) found.”
done
done
}

# Test if SCSI device $host $channen $id $lun exists
# Outputs description from /proc/scsi/scsi, returns new
testexist ()
{
grepstr=”scsi$host Channel: 0*$channel Id: 0*$id Lun: 0*$lun”
new=`cat /proc/scsi/scsi | grep -e”$grepstr”`
if test ! -z “$new”; then
cat /proc/scsi/scsi | grep -e”$grepstr”
cat /proc/scsi/scsi | grep -A2 -e”$grepstr” | tail -n2 | pr -o4 -l1
fi
}

# Perform search (scan $host)
dosearch ()
{
for channel in $channelsearch; do
for id in $idsearch; do
for lun in $lunsearch; do
new=
devnr=”$host $channel $id $lun”
echo “Scanning for device $devnr …”
printf “${yellow}OLD: $norm”
testexist
if test ! -z “$remove” -a ! -z “$new”; then
# Device exists and we’re in remove mode, so remove and readd
echo “scsi remove-single-device $devnr” >/proc/scsi/scsi
echo “scsi add-single-device $devnr” >/proc/scsi/scsi
printf “rx1b[Ax1b[Ax1b[A${yellow}OLD: $norm”
testexist
if test -z “$new”; then
printf “r${red}DEL: $normrnnnn”; let rmvd+=1;
fi
fi
if test -z “$new”; then
# Device does not exist, try to add
printf “r${green}NEW: $norm”
echo “scsi add-single-device $devnr” >/proc/scsi/scsi
testexist
if test -z “$new”; then
# Device not present
printf “rx1b[A”;
# Optimization: if lun==0, stop here (only if in non-remove mode)
if test $lun = 0 -a -z “$remove” -a $optscan = 1; then
break;
fi
else
let found+=1;
fi
fi
done
done
done
}

# main
if test @$1 = @–help -o @$1 = @-h -o @$1 = @-?; then
echo “Usage: rescan-scsi-bus.sh [options] [host [host …]]”
echo “Options:”
echo ” -l activates scanning for LUNs 0-7 [default: 0]”
echo ” -w scan for target device IDs 0 .. 15 [default: 0-7]”
echo ” -c enables scanning of channels 0 1 [default: 0]”
echo ” -r enables removing of devices [default: disabled]”
echo “–remove: same as -r”
echo “–nooptscan: don’t stop looking for LUNs is 0 is not found”
echo “–color: use coloured prefixes OLD/NEW/DEL”
echo “–hosts=LIST: Scan only host(s) in LIST”
echo “–channels=LIST: Scan only channel(s) in LIST”
echo “–ids=LIST: Scan only target ID(s) in LIST”
echo “–luns=LIST: Scan only lun(s) in LIST”
echo ” Host numbers may thus be specified either directly on cmd line (deprecated) or”
echo ” or with the –hosts=LIST parameter (recommended).”
echo “LIST: A[-B][,C[-D]]… is a comma separated list of single values and ranges”
echo ” (No spaces allowed.)”
exit 0
fi

expandlist ()
{
list=$1
result=””
first=${list%%,*}
rest=${list#*,}
while test ! -z “$first”; do
beg=${first%%-*};
if test “$beg” = “$first”; then
result=”$result $beg”;
else
end=${first#*-}
result=”$result `seq $beg $end`”
fi
test “$rest” = “$first” && rest=””
first=${rest%%,*}
rest=${rest#*,}
done
echo $result
}

if test ! -d /proc/scsi/; then
echo “Error: SCSI subsystem not active”
exit 1
fi

# defaults
unsetcolor
lunsearch=”0″
idsearch=`seq 0 7`
channelsearch=”0″
remove=””
optscan=1
if test -d /sys/class/scsi_host; then
findhosts_26
else
findhosts
fi

# Scan options
opt=”$1″
while test ! -z “$opt” -a -z “${opt##-*}”; do
opt=${opt#-}
case “$opt” in
l) lunsearch=`seq 0 7` ;;
w) idsearch=`seq 0 15` ;;
c) channelsearch=”0 1″ ;;
r) remove=1 ;;
-remove) remove=1 ;;
-hosts=*) arg=${opt#-hosts=}; hosts=`expandlist $arg` ;;
-channels=*) arg=${opt#-channels=};channelsearch=`expandlist $arg` ;;
-ids=*) arg=${opt#-ids=}; idsearch=`expandlist $arg` ;;
-luns=*) arg=${opt#-luns=}; lunsearch=`expandlist $arg` ;;
-color) setcolor ;;
-nooptscan) optscan=0 ;;
*) echo “Unknown option -$opt !” ;;
esac
shift
opt=”$1″
done

# Hosts given ?
if test “@$1” != “@”; then
hosts=$*;
fi

echo “Scanning hosts $hosts channels $channelsearch for ”
echo ” SCSI target IDs ” $idsearch “, LUNs ” $lunsearch
test -z “$remove” || echo ” and remove devices that have disappeared”
declare -i found=0
declare -i rmvd=0
for host in $hosts; do
dosearch;
done
echo “$found new device(s) found. ”
echo “$rmvd device(s) removed. ”

About Michael
Michael Wilmsen is a VMware training/consultant (no specific order) with more than 15 years in the IT industry. Main focus is VMware vSphere, Horizon View and Site Recovery Manager with a deepdive to performance. Michael is VCDX 210, VCAP 4/5 certified, has been rewarded with the vExpert title from 2011, is a PernixPro, Nutanix Tech Champion and a Nutanix Platform Professional.

8 Comments to “Script for rescanning new (virtual) disk in Linux”

  1. By Willem, December 12, 2009 @ 13:56

    Hi Mike,

    This is general Linux I’ thinking? With SLEx/OES2 the rescan scsi script should do the job? Just checking 😉

    Cheers,
    Willem

  2. By Willem, December 12, 2009 @ 13:56

    Hi Mike,

    This is general Linux I’ thinking? With SLEx/OES2 the rescan scsi script should do the job? Just checking 😉

    Cheers,
    Willem

  3. By Alex Peeters, December 14, 2009 @ 14:59

    Hey Mike,

    Good work; I was wondering if this script can also be used to notify Linux about an increase in diskspace?

    Last week I tried to increase the size on an NSS volume, but the inceased size on the LUN was only visible after a reboot of the cluster node.

    Being a NetWare guy; I was looking for a way to do it online, without the reboot.

    Kind regards,

    Alex Peeters

  4. By Alex Peeters, December 14, 2009 @ 14:59

    Hey Mike,

    Good work; I was wondering if this script can also be used to notify Linux about an increase in diskspace?

    Last week I tried to increase the size on an NSS volume, but the inceased size on the LUN was only visible after a reboot of the cluster node.

    Being a NetWare guy; I was looking for a way to do it online, without the reboot.

    Kind regards,

    Alex Peeters

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