Linux Day-3

Package Management in Linux:

Package management is a method of installing, updating**,** removing, and keeping track of software updates from specific repositories (repos) in the Linux system. Linux distros often use different package management tools such as RPM and Yum.

RPM :

Redhat Package Management
RPM is a default open-source package management utility for RedHat-based systems like (RHEL, CentOS and Fedora). The tool allows system administrators and users to install, update, uninstall, query, verify and manage system software packages in Unix/Linux operating systems. The RPM was formerly known as a **.**rpm file.
# rpm -q -a q= query , a= all.

It will list down all installed software in the OS.
- #rpm -q firefox
  
  #rpm -q -l firefox l= longlist.
  
  #rpm -q -i firefox i= information
  
  #rpm -e firefox e= erase/uninstall
  - **When we try to install Firefox with #rpm -i Firefox in a newly installed OS, we get this error message. [root@localhost ~]# rpm -i Firefox
    
    error: open of Firefox failed: No such file or directory.
  - To install any software we need the RHEL iOS image file which we use to install OS in a virtual box. We have attached an iOS image in a virtual box.
  - Open virtual box > Devices > Optical Drivers > choose/create a disk image. Once added go to Files > RHEL ios (left side) > Appstreams > Packages. Open Packages and double-click on the software you want to install.
  - We can perform the same through the command line.
    
    #df Copy the RHEL ios file path
    
    #cd path
    
    #ls
    
    #cd Appstream/
    
    #cd packages/
    
    #rpm -i firefox.... i= install - Normal installation
    
    #rpm -i -v firefox.... v= verbose -shows background process
    
    #rpm -ivh firefox... installation progress hash

** Take Screenshots in Linux: We use the gnome command to take screenshots in Linux.

#gnome-screenshot - take screenshot

#which gnome-screenshot - Where it located.

#gnome-screenshot -f /root/folder1/s1.png - save screenshot on specific location

#gnome-screenshot -f /root/folder1/ new.png --delay=20 - Screenshot after 20 sec

** Special Notes:

ctrl+s = it will hide the command you type on terminal
ctrl+q = To check all hidden commands output.

YUM:

Yellowdog Updated Modified.
YUM is an open-source command line as well as a graphical-based package management tool for RPM-based Linux systems.

It allows users and system administrators to easily install, update, remove or search software packages on a system.
YUM relies on an online repository for installing packages.
Before using the yum command, need to enable the repositories in /etc/yum.repos.d . This is a one-time task before using yum the first time.
When we try to use the yum command without enabling repositories.