Convert Cisco Bin To Qcow2

Here’s a structured technical guide for converting a Cisco .bin image (typically an IOS or IOS-XE firmware) into a qcow2 disk image, suitable for use in KVM/QEMU (like GNS3, EVE-NG, or standalone QEMU).

Create empty qcow2

qemu-img create -f qcow2 "$QCOW2_FILE" "$DISK_SIZE"

Troubleshooting Common Pitfalls

• Boot Loop: If the converted image boots to a black screen, the issue is usually the bootloader. The .bin file expects specific hardware identifiers. You may need to pass CPU flags to QEMU, such as -cpu host or specific NIC models (e.g., e1000 or virtio).
• Licensing: Some IOS-XE images check for a "trust" file in the filesystem. When extracting and repacking, ensure hidden directories (.pkg, .trust) are preserved.
• Architecture Mismatch: Be aware that Classic IOS (MIPS architecture) cannot run natively on x86 KVM. It requires an emulator like Dynamips. QCOW2 conversion is primarily effective for IOS-XE, NX-OS, and CSR1000v, which are x86-native.

Partition (use fdisk or parted)

sudo parted /dev/nbd0 mklabel msdos sudo parted /dev/nbd0 mkpart primary ext4 1MiB 100% sudo mkfs.ext4 /dev/nbd0p1

Why Convert? The Benefits of QCOW2

Converting to QCOW2 offers three distinct advantages over running raw BIN files or using legacy wrappers: convert cisco bin to qcow2

1. Snapshot Capability This is the "killer feature." With a .bin file, if you misconfigure a router, you must reload the image. With a QCOW2 image running on KVM, you can take an instant snapshot of the VM state.

• Scenario: You are testing a complex BGP migration. You snapshot the router, apply the config, and if the network crashes, you revert the snapshot in seconds.

2. Efficient Storage (Copy-On-Write) QCOW2 only stores changes made to the disk.

• You can have one "Master" read-only image (e.g., ios-17-base.qcow2).
• Every new lab VM you create points to this master file and only saves the differences.
• Result: A 2GB image can spawn 20 labs, consuming only 2GB + (changes), rather than 40GB.

3. Hypervisor Agnosticism Once converted, the image is no longer tied to GNS3 or Cisco hardware. It can be imported into: Here’s a structured technical guide for converting a Cisco

• OpenStack (for massive scale network labs).
• Proxmox VE (for home labs).
• libvirt/virt-manager (for standard Linux virtualization).

2. Prerequisites

To perform the conversion, the following environment and tools are required:

• Operating System: A Linux environment (Ubuntu, Debian, Kali, or CentOS) is highly recommended. Windows users should utilize the Windows Subsystem for Linux (WSL).
• Core Tools:
  • qemu-utils (specifically qemu-img).
  • binwalk (for firmware analysis and extraction).
  • unzip, gzip, squashfs-tools (for filesystem extraction).
• Source File: A Cisco IOS .bin file (e.g., c7200-adventerprisek9-mz.152-4.S6.bin).

Correct Approach for CSR1000v / IOS-XE:

Some Cisco images require extraction:

1. Use unzip or tar if applicable:

   tar -xvf image.bin
   

   Extract vmlinuz and iosxe-rootfs.

2. Then create qcow2 with those two files + GRUB pointing to kernel + initrd.

Part 5: Advanced Hack – IOL to QEMU (for IOS on Linux)

Cisco’s IOS on Linux (IOL) images (usually .bin files for L2/L3) run natively on Linux using a wrapper called i86bi_linux. These can be converted to .qcow2 using a chroot jail. Create empty qcow2 qemu-img create -f qcow2 "$QCOW2_FILE"