User Management

Password (Check /etc/passwd)

Adding User

• Add user to sudoers
  • add user directly to sudoers
  • add user file to sudoers.d: it is better to have users here as the distribution update can overwrite the "sudoers" file.

File Permission (chmod)

https://www.pluralsight.com/blog/it-ops/linux-file-permissions

Owner/Group/Everyone r(4)/w(2)/x(1) 700 --> rwx------ 644 --> rw-r--r--

Change Owner (chown)

Change Group (chgrp)

User Permission (usermod)

• we can add user to sudoers or add user to group that has the specific permissions.

man page

• man -wK "String for search"
• man -wk command
• apropos command

public Key Encryption

Local Machine --> Private Key Server --> Public Key

1. (local) ssh-keygen
2. (local) two files are created: example exampleAuth & exampleAuth.pub
3. exampleAuth.pub is going to be copied in Server
4. (Server) touch ~/.ssh/authorized_key
5. copy&paste exampleAuth.pub to it
6. (Server) chmod 700 .shh folder
7. (Server) chmod 644 ~/.ssh/authorized_key file
8. (local) ssh user@server-ip -p serverPort -i <path-to-private-key(exampleAuth)>
9. (Server) disable basic password login
10. (Server) edit file /etc/ssh/ssh_config and change PasswordAuthentication to no
11. (Server) restart ssh service service ssh restart or systemctl restart ssh

Link

• https://help.ubuntu.com/community/Sudoers
• https://developers.redhat.com/blog/2018/08/15/how-to-enable-sudo-on-rhel/
• https://access.redhat.com/documentation/en-US/Red_Hat_Enterprise_Linux_OpenStack_Platform/2/html/Getting_Started_Guide/ch02s03.html