General Notes:

• Can be list with: env, set, or printev.
• Important environment variables:
  • HOME: User’s home directory.
  • PATH: Ordered list of directories to search for porgrams to run.
  • PS1: Command line prompt.
  • SHELL: User’s default shell.
  • EDITOR: User’s default editor.

Files ACLS:

getfacl /path/to/file
setfacl -m u:username:permissions /path/to/file

LDAP users and groups

Components:

• Entry (or object): every unit in LDAP considered an entry.
• dn: the entry name.
• o: Organization Name.
• dc: Domain Component. For example, you can write example.com like this dc=example,dc=com.
• cn: Common Name like the person name or name of some object. To install the script:

  sudo apt install ldapscripts
  

  Script locates at /etc/ldapscripts/ldapscripts.conf. Adjust SERVER and SUFFIX to suit directory structure.

• Create a new user:

  sudo ldapaddgroup george
  sudo ldapadduser george george
  

• Change password:

  sudo ldapsetpasswd george
  

• Delete an user:

  sudo ldapdeleteuser george
  

Managing users limits

Users can be manage various limits in /etc/security/limits.conf

How to set environment variables:

• Run VARIABLE=value
• To add a new variable permanently. Edit ~/.bashrc to include VARIABLE=value and then start a new shell.

How to export environment variables:

• By default, variables created within a script are only available to the current shell. Sub-shells do not have access by default.
• To export a variable: export VAR=value or VAR=value; export VAR
• To modify a variable
  

The child process is allowed to modify exported variables, but the change in this case will not propagate back to the parent shell.

History command:

• Show the previous commands.
• Locates at ~/.bash_history
• Maximum number of lines in the history file stored at the variable HISTFILESIZE
• Maximum number of lines of history list in the current session: HISTSIZE
• Use CTRL+R or history and grep to search history commands.
• Use ! to start a history substitution
• Use !n to refer to the n-th command line
• Use !string to refer to the most recent command starting starting with the string.

Alias:

• Aliases permit custom definitions.
• alias command show all current alias
• To assign an alias: alias name=command
• Make an alias persistent in ~/.bashrc
• unalias to get rid of one.

How to grant root access?

sudo visudo
>> <username> ALL=(ALL) NOPASSWD:ALL