sysAdmin-Linux

#A good admin support both Windows and Linux user simulatenously. Even though it sound like the task is assigned for "IT-support".

1. Setting up vagrant

sudo dnf install vagrant
mkdir vagrant
cd vagrant
vagrant box add ubuntu/focal64			//You can choose another distribution similarly
vagrant up					//Vagarnt sucks for some reason.

2. Setting up Ngnix in Redhat based distros

sudo dnf install ngnix
sudo mkdir /etc/nginx/sites-available		//In debain based distro, we have this folder by default
sudo mkdri /etc/nginx/sites-enabled		//"	"	"	"	"	"	"
sudo nano /etc/nginx/nginx.conf			//Edit the http block and the line below:

include /etc/nginx/sites-enabled/*;		

[Note: all files will be inside "sites-available" and we've to create symlink inside sites enabled]

3. Setup Docker					// Don't use Docker when Podman exist.

sudo dnf install moby-engine			//weird
sudo docker login				//optional
sudo docker pull <distro>:<version>		//Will install distro.	ex: sudo docker pull ubuntu:20.04
sudo docker run -it <distro>			//Will run the distro.	ex: sudo docker run -it ubuntu
exit						//Will close container.
sudo docker attach <container_id>		//Will link two or more terminal running same docker

[Note: Docker image uses the same kernel which host OS has. Distros which run inside docker container doesn't have its own kernel.]
[Note: Since docker requires root permission to do things, rather use Podman which is compatible to almost all Docker command.]

4. Keep a log of command you type

script						//will start recording commands
exit						//will stop recording commands

[Start-Transcript and Stop-Transcript is command-line tools that can be used in Windows.]

5. Make a SSH connection to a computer if you have login credentials

ssh <username>@<ip> -p <>		//example: ssh ubuntu@13.126.30.126 -p 22

[For more: curl cht.sh/ssh]

6. Setup MySQL

sudo dnf install community-mysql-common				//"common" will install all necessary packages
sudo systemctl start mysqld					//Optional
mysql_secure_installation					//Setup root password, previleges, etc.
create user 'pranav'@'localhost' identified by 'bhattarai'	//will create mysql user named "pranav" with password named "bhattarai"
mysql -u <username> -p						//Try to avoid using "sudo" in any mysql command
	
[MariaDB is a great fork of MySQL which provides all advance features. So learn MariaDB instead, or even better learn PostgreSQL.]

7. Head, Tail & Tailf command to see logs

head -4 /path/to/log		// to see 4 log entries from the beginning
tail -5 /path/to/log		// to see 5 log entries form the ending
tailf /path/to/log		// to see realtime change in log

[For more: curl cht.sh/<command>]

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8. Indentifying network loss/drop

mtr google.com			//mtr is an opensource utility tool which merges the functionality of 'traceroute' & 'ping'.

[For more: curl cht.sh/mtr]

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9. Watch the command

watch ls			//See realtime change in new files/folder being created since "watch" will refresh at every 2 sec.

[Watch will work with almost any other command. Just type 'watch' before the command.]

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10. Set up date and time through command:

sudo date -s "<year>-<month>-<day> hour:min:sec"	ex: sudo date -s 2023-04-02 01:40:00

[ you can use "timedatectl" command to see local time, Universal time, time zone, etc.]

11. See harddisk health / status using smartctl

sudo smartctl -i /dev/sda		// to see if harddisk has SMART capability
sudo smartctl -d ata -H /dev/sda	// to run overall health ckeckup

[learn more... : sudo smartctl -x /dev/sda ]

12. Add or Remove services from Firewall policy

sudo firewall-cmd -add-service=<service_name>
sudo firewall-cmd reload
sudo firewall-cmd -remove-service=<service_name>
sudo firewall-cmd --reload

[Learned something while trying to enable "tftp" service.]

13.