.bashrc vs rc.local vs .profile — Usecases that you didn’t know

Did you know that you can automate scripts using ~/.bashrc /etc/rc.local ~/.profile. But the three are not the same.

Overall difference

The difference is in who they are run as and when they are run as. The rc.local is run during the change of run level and it runs as a privileged root user, whereas the bashrc is a bash specific file and runs when an interactive shell that is non-login shell is opened as a particular user.

/etc/rc.local

The script /etc/rc.local is for use by the system administrator. It is traditionally executed after all the normal system services are started, at the end of the process of switching to a multiuser runlevel. You might use it to start a custom service, for example a server that’s installed in /usr/local. Most installations don’t need /etc/rc.local, it’s provided for the minority of cases where it’s needed.

*What is a run level? You may ask. Article on it coming soon.*

Some use cases of the file would be:

1. To run a set of commands on boot everytime
2. To start custom services manually, that aren’t started automatically on boot
3. To log boot details to a file
4. To take backup of any files on boot
5. To run any scripts that are necessary

~/.bashrc

When an interactive shell that is not a login shell is started, bash reads and executes commands from ~/.bashrc, it is bash specific, if that file exists. This may be inhibited by using the — norc option. The — rcfile file option will force bash to read and execute commands from file instead of ~/.bashrc. — from MAN pages

Some use cases of the file would be:

1. Print the server stats like memory, free disk
2. Customize the bash terminal ( like the colors )
3. Show any new emails to the user
4. Display a custom greeting or motd
5. Show the running/suspended jobs
6. Set aliases like alias rm='rm -i'

For more examples on this, please refer to: https://tldp.org/LDP/abs/html/sample-bashrc.html

~/.profile or ~/.bash_profile or ~/bash_login

This is when the user logs in. This is most appropriate if the user wants to change his personal Linux environment.

Some use cases of the file would be:

1. Customize the PATH variable
2. Set the custom path to Global Variables or applications
3. Other use cases from the above two files can also be achieved here

Are they the same? When do I use what?

Good Question. In short, if you want to automate something

i. When the system boots: /etc/rc.local

ii. When a user logs in: ~/.profile

iii. When the user starts a bash shell: ~/.bashrc

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