Linux Network & Process Management (October 25, 2023)

 E02(Linux Network and Process Management)

Process; 

- a running program that is being executed by the Linux kernel.   

- each process has its own unique process ID(PID) and its own set of resources, such as memory and CPU time. 

- PID is the unique identifier given to a process

Process state;

One of the following states is possible for a process in the system:

Running: The program is now being run.

Ready: It is prepared to operate but is awaiting CPU time.

Sleeping: It is briefly put on hold as it waits for an action or procedure to complete.

Stopped: It has been stopped, either by the user or the system.

Zombie: The process has finished running, but there is still a record in the process table.

Process management;

Ps - report the snapshot of the current process 

- ps 

- ps aux 

- ps aux | grep username

- cat /proc/<PID>/status 

top - display all the information about all the running processes 

- top 

- top -u root

- top -u username 

gnome-system-monitor 

Kill - used to stop the process

- kill <PID> 

- kill -9 <PID>

Systemctl - make use of it when you have services installed  in your system 

- sudo systemctl status service_name 

- sudo systemctl start service_name 

- sudo systemctl stop service_name 

Network Configuration;

- ifconfig, ip addr, and ip link - can be used to access the network interfaces

- ip route - can be used to access the routing information of the network that your device is connected to. 
- /etc/netplan - can be used to access the configuration inside the folder. 

 YAML - will default configuration 

NetworkManager - used by default to manage your network 

- /etc/NetworkManager/system-connections/<connection-name> - can be used to get the configuration of the specific network you are connected to

- /etc/host.conf - contains the order in which hostnames are resolved

-  /etc/hosts - map ip address to hostname/domain name /etc/hostname - contains the name of your system hostname which can be used to identify your system in the network. 

- Some of the other files are /etc/hosts.deny and /etc/hosts. allow

Network Commands;

- netstat - used to display the various network informations

- ping - test host connection reachability 

- tracerout - find the path b/w the source and the destination 

- nslookup - get the mapping b/w ip address & the domain name and vice versa

- ssh - remote login using shell

Firewall Configuration;

ufw - bult-in command 

- sudo ufw status 

- sudo ufw enable 

To block certain website 

- sudo ufw deny out to <ip address> 

- sudo ufw reload 

To unblock the website 

- sudo ufw delete deny out to <ip address>

To disable the firewall 

- sudo ufw disable