If you at anytime need to know if a specific package is installed or not on your machine you can use the following command to get the list of all packages already installed:
Example: Using CentOS 7.2
For example, we want to know if the package of the editor “nano” is already installed or not, you can get the entire list and check if there is the package as the following example,
[root@ebsconnectors home]# rpm -qa
Or you can use the same command specifying the name of the package that you want to know if it is already installed or not wth the following command:
root@ebsconnectors home]# rpm -qa *nano*
All packages on this distributions (CentOS / RHEL) are “rpm“, and this is the main command here, you can use the rpm command with some other parameters to get more information.
If you need more help use the following command and read how to use it.
[root@ebsconnectors home]# man rpm