aptitude:tldr:2b713

The command aptitude hold '?installed(${package})' is used to put a specific package on hold in the APT package management system.

Here's a breakdown of the command:

• aptitude is the package management tool used in Debian-based systems to handle software installation, removal, and updates.
• hold is the command used with aptitude to put a package on hold.
• ' and " are used to delimit the command, ensuring that it is executed as a whole.
• ?installed(${package}) is an expression that checks if a package is already installed. ${package} is a placeholder for the name of the package you want to put on hold.

By using this command, you can prevent a particular package from being upgraded or removed automatically when running system updates. It is useful when you want to maintain a specific version of a package for some reason, such as compatibility or stability.