Ubuntu – How to create an .img file from .iso on Ubuntu

disk-imageiso

I would like to create an .img file containing Ubuntu 13.10. I know how to get the .iso, but instructions for how to 'convert' it to .img I only found under Mac (see, for example, here) — however, I work on Ubuntu 13.10. Which are the steps necessary to create the .img file?

Background information: I would like to use the .img to run it with Complete Linux Installer on Android. Complete Linux Installer already offers .img files (see here), but they are too small. Ubuntu only "sees" the size of the .img file which is far too small to be productive — which is why I would like to create a larger .img file. Using resize2fs myImage.img 4G, I tried to make the image larger, but Ubuntu run from such an image still believes the .img is small, so my hope is that by creating a larger .img right away, Ubuntu "sees" the larger space. I know I'm on thin ice here…

Best Answer

I would take a stab in the dark, but you are trying to make an img file from an iso, right? If that's the case then there isn't any difference between iso's and img's apart the extension:

There is no difference in the structure of ISO and IMG formats if the IMG file is uncompressed. It is possible for an IMG format file to be renamed with the ISO file extension and then opened in software that only recognizes the ISO file format. This is an effective way of accessing disc information in programs that do not handle the IMG format.

(source)

Wikipedia also seems to agree:

ISO images are another type of optical disc image files, which commonly use the .iso file extension, but sometimes use the .img file extension as well. They are similar to the raw optical disc images, but contain only one track with computer data obtained from an optical disc. They can not contain multiple tracks, nor audio or video tracks. They also do not contain the control headers and error correction fields of CD-ROM or DVD sectors that raw disc images usually store. Their internal format follows the structure of an optical disc file system, commonly ISO 9660 (for CDs) or UDF (for DVDs). The CUE/BIN and CCD/IMG formats, which usually contain raw disc images, can also store ISO images instead.

So, how to convert an iso to img? Just change the extension:

rename 's/\.iso(?=[^.iso]*$)/.img/g' *

Now, to create an img, you should use dd and save it into a file called img.

Creating the blank image

Create the blank image:

dd if=/dev/zero of=image.img iflag=fullblock bs=1M count=100 && sync

ubuntu@ubuntu ~/tmp % dd if=/dev/zero of=image.img iflag=fullblock bs=1M count=100 && sync
100+0 records in
100+0 records out
104857600 bytes (105 MB) copied, 0.0415825 s, 2.5 GB/s
ubuntu@ubuntu ~/tmp % tree
.
└── image.img

0 directories, 1 file

Mounting the blank image

List the already busy loopback devices:

losetup

ubuntu@ubuntu ~/tmp % losetup                   
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE
/dev/loop0         0      0         0  1 /cdrom/casper/filesystem.squashfs

Mount the image on the first available loopback device:

sudo losetup loop1 image.img

ubuntu@ubuntu ~/tmp % sudo losetup loop1 image.img
ubuntu@ubuntu ~/tmp % losetup
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE
/dev/loop0         0      0         0  1 /cdrom/casper/filesystem.squashfs
/dev/loop1         0      0         0  0 /home/ubuntu/tmp/image.img

Partitioning / formatting the blank image

Run gparted passing the loopback device as an argument:

sudo -H gparted /dev/loop1

Click on "Device" -> "Create Partition Table...":

Click "Apply":

Click on "Partition" -> "New":

Select "fat32" from the drop-down menu:

Click "Add":

Click the green tick:

Click "Apply":

Click "Close":

And close Gparted.

Unmounting the image

Finally, unmount the image from the loopback device:

sudo losetup -d /dev/loop1

ubuntu@ubuntu ~/tmp % sudo losetup -d /dev/loop1
ubuntu@ubuntu ~/tmp % losetup
NAME       SIZELIMIT OFFSET AUTOCLEAR RO BACK-FILE
/dev/loop0         0      0         1  1 /cdrom/casper/filesystem.squashfs

You can use the created image for whatever purpose you want; for example, you can use it as a virtual USB drive:

sudo losetup loop1 image.img

Opening Files:

Ubuntu – How to boot an USB installer ISO image from an internal SSD

Get the uuid of the partition on the disk:

sudo blkid
/dev/sda1: UUID="6f2b5b8c-f0af-4d4d-a32b-2481a9e2c5d7" TYPE="ext4" PARTUUID="694a694a-05"

Store the ISO in the root of the partition, in this example we will use ubuntu-19.04-desktop-amd64.iso.

Mount the ISO and copy the first menuentry from /boot/grub/grub.cfg, and paste it in /etc/grub.d/40_custom:

#!/bin/sh
exec tail -n +3 $0
# This file provides an easy way to add custom menu entries.  Simply type the
# menu entries you want to add after this comment.  Be careful not to change
# the 'exec tail' line above.

menuentry "Try Ubuntu without installing" {
    set gfxpayload=keep
    linux   /casper/vmlinuz  file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash ---
    initrd  /casper/initrd
}

Change the following in bold:

menuentry "Try Ubuntu without installing" {
                                             # the uuid you got i step 1
    search --no-floppy --fs-uuid --set=root 6f2b5b8c-f0af-4d4d-a32b-2481a9e2c5d7
    set iso_path=/ubuntu-19.04-desktop-amd64.iso
    loopback loop $iso_path
    set gfxpayload=keep
    linux   (loop)/casper/vmlinuz  file=/cdrom/preseed/ubuntu.seed boot=casper quiet splash iso-scan/filename=$iso_path ---
    initrd  (loop)/casper/initrd
}

Update grub:
```
sudo update-grub
```

Next time you reboot you will have an entry to boot the ISO.

Best Answer

Related Solutions

Ubuntu – Create blank disk image for file storage

Creating the blank image

Mounting the blank image

Partitioning / formatting the blank image

Unmounting the image

Ubuntu – How to boot an USB installer ISO image from an internal SSD

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