(Source: https://pythonrepo.com/repo/BentonEdmondson-knock-python-command-line-tools)

This software does not utilize Adobe Digital Editions nor Wine. It is completely free and open-source software written natively for Linux.

For NixOS User

1. Create a free Adobe account here if you do not already have one.
2. Install the software. For NixOS, include this flake in your system flake.nix. Then run knock ~/path/to/my-book.acsm to use.

inputs.knock.url = github:BentonEdmondson/knock
outputs = { self, knock }: { /* knock.defaultPackage.x86_64-linux is the package */ }

For non-NixOS

Use the latest release. It is large because it includes all dependencies, allowing it to run on any system with an x86_64 Linux kernel. It was built using nix bundle. Use it by doing the following: Download knock-version-x8664-linux and open a terminal

• Navigate to the folder within which knock-version-x86_64-linux resides (e.g. cd ~/Downloads)
• Run mv knock-version-x86_64-linux knock to rename it to knock
• Run chmod +x knock to make it executable
• Run ./knock ~/path/to/my-book.acsm to convert the ebook

If you receive an error that says something like ./nix/store/...: not found or ./nix/store/...: No such file or directory then you might not have user namespaces enabled. Try running the following to fix it:

# echo "kernel.unprivileged_userns_clone=1" >> /etc/sysctl.conf
# reboot

Enter in your Adobe email and password when prompted

Optionally move the executable to ~/bin (for your user) or /usr/local/bin/ (for all users) to allow it to run from anywhere (might not work on some distributions)

Verified Book Sources

Knock should work on any ACSM file, but it has been specifically verified to work on ACSM EPUB files from the following:

• eBooks.com
• Rakuten Kobo
• Google Books
• Hugendubel.de (German)

The resulting EPUB file can be read with any EPUB reader.

Legality

It's Perfectly Legal to Tell People How to Remove DRM (Gizmodo)

Do not use this software for piracy; this software is not intended for piracy. This software exists to allow readers to legally purchase and then legally and freely read ebooks. I suspect that the significant prevalence of ebook piracy is caused in large part by the restrictions put on legally purchased ebooks. This software exists to incentivize the legal purchase of ebooks by enabling their unrestricted and legal consumption.