Welcome to Linux!

Описание на русском тут

1. Part 1. OS installation
2. Part 2. Creating a user
3. Part 3. OS Network Setup
4. Part 4. OS Update
5. Part 5. Using the sudo command
6. Part 6. Installing and configuring the Time Service
7. Part 7. Installing and using text editors
8. Part 8. Installation and basic configuration of the SSHD service
9. Part 9. Installing and using top, htop utilities
10. Part 10. Using the fdisk utility
11. Part 11. Using the df utility
12. Part 12. Using the du utility
13. Part 13. Installing and using the ncdu utility
14. Part 14. Working with system logs
15. Part 15. Using the CRON Task Scheduler

Part 1. Installing the OS

• Installing Ubuntu 20.04 Server LTS.
• Output of the Ubuntu version using the cat /etc/issue command :

Part 2. Creating a user

• Create a new user admin:

• Adding the user admin to the 'adm` group

• We output users with the command cat /etc/passwd, look at the presence of the user admin there:

Part 3. Configuring the OS network

• lo is an interface that allows programs to access through a local host or send data to themselves. This is useful for testing and setting up network functions.
• DHCP is a network protocol for dynamically configuring network parameters. It was created so that you do not have to manually set IP, DNS, and so on for each device.
• First, go to the *** superuser*** so as not to type sudo every time and use it further in all tasks.
• Use ip route to get the gateway address, set static parameters in the file /etc/netplan/*.yaml, apply the changes netplan apply, reboot the machine reboot, check that the specified parameters are preserved.
• Ping 1.1.1.1 and ya.ru:

Part 4. OS Update

• Check for apt update' updates, install apt upgrade`:

Part 5. Using the sudo command

• sudo is used to execute commands on behalf of the superuser. The superuser has full control over the system.
• Add the user admin to the `sudo' group and switch to it, change the hostname. Result:

Part 6. Installing and configuring the Time service

• If auto-synchronization of time is not enabled, turn it on. Result:

Part 7. Installing and using text editors VIM, NANO, MCEDIT

• VIM, to exit with saving :wq

• NANO, to exit with saving Ctrl + O

• MCEDIT, to exit with saving Esc + 0 , Y

• VIM, to exit without saving :q!

• NANO, to exit without saving Ctrl + X , N

• MCEDIT, to exit without saving Esc + 0 , N

• VIM, search for /jenniffr and replace :s/jenniffr/21 School 21/g

• NANO, search for Ctrl + W and replace Ctrl +\

• MCEDIT, search for Esc + 7 and replace Esc + 4

Part 8. Installation and basic configuration of the SSHD service

• Install ssh, add it to autorun, look at running processes using ps -ef
  • ps: running processes

• -e: processes of all users
• -f: complete information about each process

• Using netstat -tan
  • netstat - disables network connections

• -t - TCP connections only
• -a - display all connections
  • -n - display addresses and addresses in numerical representation, without converting to names

• Command output:

• Proto - Connection protocol.
  • Recv-Q - The number of bytes waiting to be read from the socket.
  • Send-Q - The number of bytes waiting to be sent over the socket.
  • `Local Address' - The local IP address and port.
  • `Foreign Address' - Local IP address and port.
  • `State' - The state of the connection.
  • The address 0.0.0.0 means "all addresses on this device".

Part 9. Installing and using the top, htop utilities

• Output top:

• uptime = 46 min
• number of authorized users = 1
  • total system load = 0.00
• total number of processes = 95
  • CPU usage = 0.00
• memory usage = 146.9
• pid of the process taking up the most memory = 657
• pid of the process taking up the most CPU time = 1559

• 'htop` screenshots:

  • sorted by PID, PERCENT_CPU, PERCENT_MEM, TIME

• filtered for the sshd process

• with the syslog process found using the search

• with added output of hostname, clock and uptime

Part 10. Using the fdisk utility

• Using the fdisk -l command, we will find out:
  • Disk name = /dev/sda

• Size = 10GiB
  • SECTORS = 20971520

Part 11. Using the df utility

• Using the df command, we find out the data about the root partition (measured in kilobytes (K))

• partition size = 8408452
  • the size of the OCCUPIED SPACE = 2594036
  • free space size = 5365700
• percentage of usage = 33%

• Using the df -Th command, we find out the data about the root partition (measured in gigabytes (G))

• partition size = 8.1
• occupied space size = 2.5
• free space size = 5.2
• percentage of usage = 33%
• file system type = ext4"

Part 12. Using the du utility

• Output of du commands:

• Output the contents of /var/log/*

Part 13. Installing and using the ncdu utility

• Output folder sizes using ncdu

• /home

• /var

• /var/log

Part 14. Working with system logs

• Last login = Jan 25 07:04 , user = jenniffr, login method = tty1

• Restart SSHd:

Part 15. Using the Task Scheduler CRON

• Add uptime to the task list every 2 minutes. Log output + cron task list:

• Deleting all tasks from cron:

If you're reading this, know this: you're doing great)

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Thank you for your time.