dracut-catimages - Linux

Overview

dracut-catimages is a powerful tool used in the creation of Linux system images by extracting and concatenating file images into a single, consolidated image. It’s primarily designed to create custom rescue and installation media based on system snapshots or specific files and directories.

Syntax

dracut-catimages [options] <output_image> <input_images>...

Options/Flags

  • -v, –verbose: Print verbose output, providing detailed information about the concatenation process.
  • -d, –dry-run: Simulate the concatenation process without making any permanent changes.
  • -o, –output-format: Specify the output image format. Supported formats include: ext3, ext4, squashfs, and initramfs. (Default: ext4)
  • -s, –skip-fs-integrity-check: Skip filesystem integrity check before concatenation. (Not recommended for production use)

Examples

Create a custom rescue image from a snapshot:

dracut-catimages -o initramfs /tmp/my_rescue_image.img /dev/sda1

Concatenate multiple file images into an ext4 image:

dracut-catimages -o ext4 /tmp/my_combined_image.img /usr/share/syslinux/mbr.bin /boot/vmlinuz-5.15.0-52-generic /boot/initrd.img-5.15.0-52-generic

Common Issues

  • Unable to mount file images: Ensure that the input file images are valid and have a supported filesystem type.
  • Concatenated image not bootable: Verify that the correct bootloader image is included in the concatenation process.
  • Filesystem corruption: Skipping the filesystem integrity check (-s) can lead to corrupted output images.

Integration

dracut-catimages can be combined with other commands to create complex image creation workflows. For example, it can be used in combination with mksquashfs to create a compressed squashfs image:

dracut-catimages -o squashfs /tmp/my_squashfs_image.img /dev/sda1 | mksquashfs /tmp/my_squashfs_image.img

Related Commands

  • dracut: Creates initial RAM disks (initramfs) used during system boot.
  • mksquashfs: Creates compressed squashfs images.
  • cat: Concatenates files and data streams.

Official documentation