What happens when a program is installed?

Question

I am posting this question with the intention of getting a comprehensive answer that explains the installation process.

Some particular questions I have about the process:

1. What's the difference between the bin folder in the root directory and the bin folder in the usr directory?
2. What needs to happen for a program to be recognized by the terminal so I can type the name of the program with options and arguments?
3. Are there any other standard directories that may be created upon the install of a program? Where are they located?

Answer 1

1. /bin contains commands that may be used by both the system administrator and by users, but which are required when no other filesystems are mounted (e.g. in single user mode). It may also contain commands which are used indirectly by scripts. /usr/bin/ is the primary directory of executable commands on the system. Source: https://unix.stackexchange.com/questions/5915/difference-between-bin-and-usr-bin

2. The executable needs to have the execute permission set properly and it needs to be located within a directory listed in the $PATH environment variable for the shell in which you are trying to execute it. For example, if your PATH contains /usr/local/bin , any executable in that folder can be run by simply typing the name of the command at the prompt.

3. This is quite variable depending on the application, but one can count on at least some information under /etc for system-wide programs that have settings files, files within your home folder for user-specific settings, man files under /usr/local/share somewhere. There could be files under /var, /opt, or pretty much anywhere else too. For a program installed from a .deb file, you can see what files it has created using deb -L packageName .

Answer 2

Information provided below can help you widely:

1. What's the difference between the bin folder in the root directory and the bin folder in the usr directory?

   • Visit : Filesystem_Hierarchy_Standard.
   • Also refer to How to understand the Ubuntu file system layout? & Differences between /bin, /sbin, /usr/bin, /usr/sbin, /usr/local/bin, /usr/local/sbin Questions.

2. What needs to happen for a program to be recognized by the terminal so I can type the name of the program with options and arguments?

   • Visit : Where should I put my script so that I can run it by a direct command? which can help: from where terminal command is executed?

   • /bin and /usr/bin are essential command binaries.

3. Are there any other standard directories that may be created upon the install of a program? Where are they located?

   • Visit : What is the Linux equivalent to Windows' Program Files? and Where can I find the location of folders for installed programs?

Additional: Most of applications desktop file exist in /usr/share/applications and alacarte is useful to find command or add/remove apps.