src/kernel/linux/v4.19/Documentation/target/target-export-device

#!/bin/sh
#
# This script illustrates the sequence of operations in configfs to
# create a very simple LIO iSCSI target with a file or block device
# backstore.
#
# (C) Copyright 2014 Christophe Vu-Brugier <cvubrugier@fastmail.fm>
#

print_usage() {
    cat <<EOF
Usage: $(basename $0) [-p PORTAL] DEVICE|FILE
Export a block device or a file as an iSCSI target with a single LUN
EOF
}

die() {
    echo $1
    exit 1
}

while getopts "hp:" arg; do
    case $arg in
        h) print_usage; exit 0;;
        p) PORTAL=${OPTARG};;
    esac
done
shift $(($OPTIND - 1))

DEVICE=$1
[ -n "$DEVICE" ] || die "Missing device or file argument"
[ -b $DEVICE -o -f $DEVICE ] || die "Invalid device or file: ${DEVICE}"
IQN="iqn.2003-01.org.linux-iscsi.$(hostname):$(basename $DEVICE)"
[ -n "$PORTAL" ] || PORTAL="0.0.0.0:3260"

CONFIGFS=/sys/kernel/config
CORE_DIR=$CONFIGFS/target/core
ISCSI_DIR=$CONFIGFS/target/iscsi

# Load the target modules and mount the config file system
lsmod | grep -q configfs || modprobe configfs
lsmod | grep -q target_core_mod || modprobe target_core_mod
mount | grep -q ^configfs || mount -t configfs none $CONFIGFS
mkdir -p $ISCSI_DIR

# Create a backstore
if [ -b $DEVICE ]; then
    BACKSTORE_DIR=$CORE_DIR/iblock_0/data
    mkdir -p $BACKSTORE_DIR
    echo "udev_path=${DEVICE}" > $BACKSTORE_DIR/control
else
    BACKSTORE_DIR=$CORE_DIR/fileio_0/data
    mkdir -p $BACKSTORE_DIR
    DEVICE_SIZE=$(du -b $DEVICE | cut -f1)
    echo "fd_dev_name=${DEVICE}" > $BACKSTORE_DIR/control
    echo "fd_dev_size=${DEVICE_SIZE}" > $BACKSTORE_DIR/control
    echo 1 > $BACKSTORE_DIR/attrib/emulate_write_cache
fi
echo 1 > $BACKSTORE_DIR/enable

# Create an iSCSI target and a target portal group (TPG)
mkdir $ISCSI_DIR/$IQN
mkdir $ISCSI_DIR/$IQN/tpgt_1/

# Create a LUN
mkdir $ISCSI_DIR/$IQN/tpgt_1/lun/lun_0
ln -s $BACKSTORE_DIR $ISCSI_DIR/$IQN/tpgt_1/lun/lun_0/data
echo 1 > $ISCSI_DIR/$IQN/tpgt_1/enable

# Create a network portal
mkdir $ISCSI_DIR/$IQN/tpgt_1/np/$PORTAL

# Disable authentication
echo 0 > $ISCSI_DIR/$IQN/tpgt_1/attrib/authentication
echo 1 > $ISCSI_DIR/$IQN/tpgt_1/attrib/generate_node_acls

# Allow write access for non authenticated initiators
echo 0 > $ISCSI_DIR/$IQN/tpgt_1/attrib/demo_mode_write_protect

echo "Target ${IQN}, portal ${PORTAL} has been created"