Complete Guide: How to Discover, Connect, Mount and Format iSCSI LUN in Red Hat Enterprise Linux 9

Complete Guide: How to Discover, Connect, Mount and Format iSCSI LUN in Red Hat Enterprise Linux 9

linux

Introduction

iSCSI (Internet Small Computer Systems Interface) is a powerful protocol that allows you to access remote storage devices over IP networks. In enterprise environments, iSCSI provides a cost-effective alternative to Fibre Channel SANs while offering excellent performance and scalability. This comprehensive guide walks you through the complete process of discovering, connecting, mounting, and formatting iSCSI LUNs (Logical Unit Numbers) in Red Hat Enterprise Linux 9.

Prerequisites

Before beginning this tutorial, ensure you have:

  • Red Hat Enterprise Linux 9 system with root privileges
  • Network connectivity to the iSCSI target server
  • Basic understanding of Linux storage concepts
  • iSCSI target server configured and accessible

What You’ll Learn

By the end of this guide, you’ll understand how to:

  • Install and configure iSCSI initiator tools
  • Discover available iSCSI targets
  • Authenticate and connect to iSCSI LUNs
  • Format and mount iSCSI storage
  • Configure persistent connections
  • Troubleshoot common iSCSI issues

Step 1: Install iSCSI Initiator Software

First, install the necessary iSCSI initiator packages on your RHEL 9 system:

# Install iscsi-initiator-utils package
sudo dnf install iscsi-initiator-utils -y

# Verify installation
rpm -qa | grep iscsi

The iscsi-initiator-utils package provides essential tools including:

  • iscsiadm: Primary command-line tool for iSCSI management
  • iscsi_discovery: Service for automatic target discovery
  • Configuration files in /etc/iscsi/

Step 2: Configure iSCSI Initiator Settings

Configure the iSCSI initiator name, which uniquely identifies your system:

# Check current initiator name
cat /etc/iscsi/initiatorname.iscsi

# Generate new initiator name (if needed)
echo "InitiatorName=$(iscsi-iname)" | sudo tee /etc/iscsi/initiatorname.iscsi

# Start and enable iscsid service
sudo systemctl start iscsid
sudo systemctl enable iscsid

Step 3: Discover iSCSI Targets

Use the iscsiadm command to discover available targets on your iSCSI server:

# Discover targets using SendTargets method
sudo iscsiadm --mode discovery --type sendtargets --portal <TARGET_IP>:3260

# Example with actual IP
sudo iscsiadm --mode discovery --type sendtargets --portal 192.168.1.100:3260

Expected output format:

192.168.1.100:3260,1 iqn.2023-01.com.example:storage.target01
192.168.1.100:3260,1 iqn.2023-01.com.example:storage.target02

To view discovered targets:

# List all discovered targets
sudo iscsiadm --mode node --op show

Step 4: Configure Authentication (Optional)

If your iSCSI target requires CHAP authentication, configure credentials:

# Set CHAP username and password for specific target
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.session.auth.authmethod --value CHAP

sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.session.auth.username --value <USERNAME>

sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.session.auth.password --value <PASSWORD>

Step 5: Connect to iSCSI Target

Establish connection to the discovered iSCSI target:

# Login to specific target
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 --login

# Example command
sudo iscsiadm --mode node --targetname iqn.2023-01.com.example:storage.target01 \
    --portal 192.168.1.100:3260 --login

Verify successful connection:

# Check active sessions
sudo iscsiadm --mode session --op show

# View detailed session information
sudo iscsiadm --mode session --op show --verbose

Step 6: Identify the New Block Device

After successful connection, identify the newly available block device:

# List all block devices
lsblk

# Check system messages for new device
dmesg | tail -20

# View SCSI devices
cat /proc/scsi/scsi

The iSCSI LUN typically appears as /dev/sdX where X is the next available letter.

Step 7: Partition the iSCSI LUN (Optional)

Create partitions on the iSCSI device if needed:

# Use fdisk to create partitions
sudo fdisk /dev/sdX

# Interactive fdisk commands:
# n - create new partition
# p - primary partition
# 1 - partition number
# [Enter] - default first sector
# [Enter] - default last sector
# w - write changes

For GPT partitioning (recommended for large disks):

# Use parted for GPT
sudo parted /dev/sdX mklabel gpt
sudo parted /dev/sdX mkpart primary 0% 100%

Step 8: Format the iSCSI LUN

Create a filesystem on the iSCSI device:

# Format with ext4 filesystem
sudo mkfs.ext4 /dev/sdX1

# Format with xfs filesystem (alternative)
sudo mkfs.xfs /dev/sdX1

# Add filesystem label
sudo e2label /dev/sdX1 "iscsi-storage"

Step 9: Create Mount Point and Mount the LUN

Create a directory and mount the formatted iSCSI LUN:

# Create mount point
sudo mkdir -p /mnt/iscsi-storage

# Mount the filesystem
sudo mount /dev/sdX1 /mnt/iscsi-storage

# Verify mount
df -h /mnt/iscsi-storage
mount | grep iscsi-storage

Step 10: Configure Persistent Mounting

To automatically mount the iSCSI LUN at boot, add an entry to /etc/fstab:

# Get device UUID
sudo blkid /dev/sdX1

# Add to fstab using UUID (recommended)
echo "UUID=<device-uuid> /mnt/iscsi-storage ext4 defaults,_netdev 0 2" | sudo tee -a /etc/fstab

# Alternative using device path
echo "/dev/sdX1 /mnt/iscsi-storage ext4 defaults,_netdev 0 2" | sudo tee -a /etc/fstab

The _netdev option ensures the filesystem is mounted after network services are available.

Step 11: Configure Automatic iSCSI Connection

Enable automatic connection to iSCSI targets at boot:

# Set automatic login for target
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.startup --value automatic

# Enable iscsi service for boot-time connections
sudo systemctl enable iscsi

Step 12: Test and Verify Configuration

Perform comprehensive testing to ensure everything works correctly:

# Test filesystem access
sudo touch /mnt/iscsi-storage/test-file
ls -la /mnt/iscsi-storage/

# Check iSCSI session status
sudo systemctl status iscsi
sudo systemctl status iscsid

# Simulate reboot test (optional)
sudo umount /mnt/iscsi-storage
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 --logout
sudo mount -a

Troubleshooting Common Issues

Connection Problems

If you encounter connection issues:

# Check network connectivity
ping <TARGET_IP>
telnet <TARGET_IP> 3260

# Review iSCSI logs
sudo journalctl -u iscsid
sudo journalctl -u iscsi

# Check firewall settings
sudo firewall-cmd --list-ports
sudo firewall-cmd --add-port=3260/tcp --permanent
sudo firewall-cmd --reload

Discovery Issues

For target discovery problems:

# Clear discovery cache
sudo rm -rf /var/lib/iscsi/send_targets/*

# Retry discovery with debug
sudo iscsiadm --mode discovery --type sendtargets --portal <TARGET_IP>:3260 --debug 8

Performance Optimization

Optimize iSCSI performance:

# Adjust iSCSI parameters
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.session.timeo.replacement_timeout --value 120

# Configure multipath (if using multiple paths)
sudo dnf install device-mapper-multipath -y
sudo mpathconf --enable --with_multipathd y

Security Best Practices

Implement these security measures:

  1. Use CHAP Authentication: Always configure CHAP authentication for production environments
  2. Network Segmentation: Deploy iSCSI traffic on dedicated VLANs
  3. Firewall Rules: Restrict access to iSCSI ports (3260/tcp)
  4. Regular Updates: Keep iSCSI initiator software updated
# Configure bidirectional CHAP
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.session.auth.authmethod --value CHAP

# Set mutual authentication
sudo iscsiadm --mode node --targetname <TARGET_IQN> --portal <TARGET_IP>:3260 \
    --op update --name node.session.auth.username_in --value <INITIATOR_USERNAME>

Managing Multiple iSCSI LUNs

For environments with multiple LUNs:

# Discover all targets from server
sudo iscsiadm --mode discovery --type sendtargets --portal <TARGET_IP>:3260

# Login to all discovered targets
sudo iscsiadm --mode node --loginall=all

# Check all active sessions
sudo iscsiadm --mode session

Conclusion

This comprehensive guide covered the complete process of working with iSCSI LUNs in Red Hat Enterprise Linux 9. You’ve learned how to discover targets, establish connections, format storage, and configure persistent mounting. These skills are essential for managing enterprise storage infrastructure and ensuring reliable data access across your network.

Remember to always test your configuration thoroughly in development environments before implementing in production. Regular monitoring and maintenance of iSCSI connections will ensure optimal performance and reliability of your storage infrastructure.

Additional Resources

  • Red Hat Enterprise Linux 9 Storage Administration Guide
  • iSCSI RFC 7143 documentation
  • RHEL 9 System Administrator’s Guide
  • Red Hat Customer Portal for enterprise support

For enterprise deployments, consider implementing monitoring solutions and automated backup strategies to protect your iSCSI-based storage infrastructure.

Related posts

Share your thoughts