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copied!<p>The operating system image in a Fedora LiveCD or LiveUSB can be mounted after exposing the embedded root filesystem. Fedora's livecd-tools package provides a utility <a href="https://github.com/rhinstaller/livecd-tools/blob/master/tools/liveimage-mount" rel="nofollow">liveimage-mount</a> that does this using Python.</p> <p>The <a href="https://fedoraproject.org/wiki/LiveOS_image" rel="nofollow">Fedora LiveOS image</a> (Live CD/USB operating system) technology uses the Device-mapper snapshot target to make a compressed, read-only copy of the root filesystem available for read-write mounting at boot time, where filesystem writes go into a temporary or persistent copy-on-write overlay. Everything is accomplished with the <code>dmsetup</code> command. LVM is not involved (although it also uses Device-mapper technology).</p> <p>A LiveOS installed device will have a /LiveOS/ directory in it's base filesystem. The /LiveOS/squashfs.img file contains a compressed (and read-only) ext4 filesystem that itself contains a /LiveOS/ directory and within that the distributed root filesystem in a file named ext3fs.img. So, the squashfs.img file contains a directory and file, /LiveOS/ext3fs.img, that itself contains the root filesystem (with /bin, /boot, /dev, /etc, /home, ...).</p> <p>If there is a persistent overlay file installed on the device, it will be saved as<br>         /LiveOS/overlay-<LABEL>-<UUID><br> where LABEL and UUID are the device partition label and UUID as reported by the following command,<br>         <code>lsblk -o LABEL,UUID</code></p> <p>One can programmatically</p> <ol> <li>loop mount the squashfs.img file, then</li> <li>set up a loop device for the ext3fs.img file found in mount 1.</li> <li>If there is no persistent overlay, you may simply mount the ext3fs.img file or loop device from<br> step 2 (the read-only, base image).</li> <li>If there is a persistent overlay file, set up a loop device for it.</li> <li><p>Determine the size of the root filesystem in units of 512-byte sectors, </p> <p><code>blockdev --getsz <basefs_loop></code></p></li> <li><p>Then setup a Device-mapper snapshot target with this general command, </p> <p><code>dmsetup create <target_name> --table "0 <size> snapshot <basefs_loop> <overlay_loop> P 8"</code></p></li> <li><p>Finally, mount the Device-mapper target on a desired mount point, </p> <p><code>mount /dev/mapper/<target_name> <mount point></code></p></li> </ol>

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