Fundamental of Computing Week 10: 16 October to 22 October (Linux Network and Process Management)

 Linux Network and Process Management

What is a Process?

  • In Linux, a process is a running program. It is a program instance that is being executed by the Linux kernel. Each process has its own unique process ID (PID) and resources like as memory and CPU time.
  • Process ID(PID) is a unique identifier assigned to a process.

Process States

  • A system process can be in one of the following states:
    • Running: it is currently running the code.
    • Ready: it is ready to run but is awaiting CPU time.
    • sleeping: it is briefly paused while waiting for some event or procedure to occur.
    • Stopped: it has been stopped by the user or the system.
    • Zombie: the process has finished but there is still an entry in the process table.

Process Management

  • The following commands can be used to manage the processes:
    • ps: report the snapshot of current process.
    • top: real time process monitor that displays the information about all running processes.
    • kill: used to stop the process.
    • systemctl: can be used if some services are installed in the system.

Network Configuration

  • Names of all the network interfaces can be obtained by using the commands ifconfig, ip addr, or ip link.
  • The command ip route allows to view the routing information for the network to which your device is connected.
  • The configuration file can be found in the /etc/netplan/ folder. I will come with a YAML configuration file by default. It manages your network by default using the NetworkMnager.
  • You can access configurations about specific network you are connected to from /etc/NetworkManaer/system-connections/<connection-name>.
  • To access the list of all the network connection names, go inside the /etc/NetworkManager/system-connections/ folder.
  • Other network configuration files are:
    • /etc/host.conf: contains order in which hostnames are resolved.
    • /etc/hosts: map ip address to hostname/domain name.
    • /etc/hostname contains name of your system hostname which can be used to identify your system in the network.
    • Some other files are /etc/hosts.deny and /etc/hosts.allow.

Network Commands

  • Other network commands that can be included are:
    • netstat: used to display various network statistics such as routing tables, interfaces, connections, and ports.
    • Ping: check the reachability of the host connection.
    • Traceroute: determines the path between the source and the destinations.
    • nslookup: retrieve a mapping between an IP address and a domain name, and vice versa.
    • ssh: shell-based remote login.

Firewall Configuration

Use ufw(uncomplicated firewall) which comes builtin.
We use the following commands for specific purposes:
    • sudo ufw enable: in case status is inactive.
    • sudo ufw reload: to reload firewall.
    • sudo ufw deny out to <ip-address>: used to block a certain website (replave the ip-address with the actual ip address of website).
    • sudo ufw delete deny out to <ip-address>: used to unblock the blocked website.
    • sudo ufw disable: used to disable firewall.
    • sudo firewall-cmd --get-zones: to view available zones on the system.
    • sudo firewall-cmd --get-default-zone: to view the default zone.
    •  sudo firewall-cmd --get-active-zone: to view the active zones and their associated interfaces and sources.




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