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Why does cubic change the extension of inirtd file on the ISO?

Asked by Cubic PPA

The extension of the initrd file has changed on the customized ISO from the initrd file extension on the original ISO.

Why does Cubic do this?

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Cubic PPA (cubic-wizard) said : 		#1

Some distros incorrectly name the initrd file with an arbitrary extension (such as *.lz or *.gz).
If the original initrd file extension is incorrect, cubic will fix the extension to accurately reflect the actual compression algorithm used to create the initrd file.

The initrd.* file is a CPIO archive (see https://en.wikipedia.org/wiki/Cpio).

In older versions of Ubuntu (prior to ~18.10) the initrd file was compressed using gzip or lzma.

Since Ubuntu 18.10, the initrd file contains multiple binary files.
Many of these files are compressed using different formats each (lzma, gzip, etc).
Ubuntu has adopted the convention exclude the extension on the initrd file, since the extension doesn't really make sense in this situation.

Nevertheless, one of the files in the initrd archive is a compressed Linux file system (containing /etc, /lib, /usr, etc.)
This file is used during the ISO bootstrap process.

Cubic updates the initrd file name extension to reflect the compression algorithm used for these Linux file system files (/etc, /lib, /usr, etc.).
Cubic will also automatically update the boot configuration files to match the corrected initrd file name; however, you should inspect the boot configurations to ensure the replacements were made accurately.

If you want to change the extension of the initrd file, follow these instructions:

https://answers.launchpad.net/cubic/+question/693009