[hemmerling] Debian Linux 2/4

Related page:

• Debian Linux 1/4.
• Debian Linux 3/4.
• Debian Linux 4/4.
• Linux 1/8.
• Linux 2/8 - Linux Distributions.
• Linux Skills & Skill Certification.

• Computer Hope. Free computer help since 1998 "Linux chmod command".
• IONOS "What is chmod?" - “chmod help & examples”.
• StackExchange "What's the difference between `chmod a+x` and `chmod +x`? [duplicate]".
  • a+x will set all the x bits of the file.
  • +x will set all the x bits of the file that are not present in the umask.
• StackExchange "Why does chmod +w not give write permission to other(o)".
• ubuntuusers - Fragen ist menschlich!.
• Warp "Chmod +X" - “Understanding Chmod +X - Making Files Executable”.
  • To make a script executable by every user on the system:

    $ chmod +x script.sh

• Default user:

  $printenv
  PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
  

• su ( root ):

  $su
  $printenv
  PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
  

• su - ( root ):

  $su -
  $printenv
  PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
  

$su -
Password:
# $apt install sudo
$usermod -aG sudo USERNAME
$getent group sudo

• Add the USERNAME ( of the user as which you are logged in ) to the group “sudoers”.
  1. ( Open a terminal ).
  2. su root
  3. ( Input root password. root is already member of the group “sudoers” ).
  4. apt-get install sudo -y
  5. su -
  6. adduser username sudo
  7. logout
  8. chmod 0440 /etc/sudoers
  9. exit
  10. sudo reboot
  11. ( Input root password ).
  12. ( reboot manually if “sudo reboot” doesn't work )

• “sudo su” & lowercase ( ”-L” ) or lowercase ( ”- -Login” ):

  sudo su -l
  sudo su --login
  

• With Debian Linux, the default user is not member of the group “sudoers”. This is unexpected, from point of use of an Ubuntu user!!!
  • If you try any administrative tasks starting with “sudo”, even after giving the right password, you are rejected by

    Username Is Not In The Sudoers File. This Incident Will Be Reported

  • Especially, the “GDebi Package Installer” quits without error message after entering the right password .
• EN.Wikipedia "su (Unix)", DE.Wikipedia "su (Unix)".
• EN.Wikipedia "sudo", DE.Wikipedia "sudo".
• Debian Wiki "sudo".
• Debian:
  • reddit "/r/linuxquestions" - "bash: usermod: command not found (in latest Debian 11 install)" - “You probably used su to become root. Try using su - instead”.
  • CloudPanel "How to Add User to Sudoers in Debian".
  • StackExchange "Username is not in the sudoers file. This incident will be reported".
  • StackExchange "bash: adduser: command not found [Debian Buster]".
  • TechRepublic "How to install sudo on a Debian minimal server".
  • Debian Forum "Unterschied su und su - root ?".
    • “Es genügt su -, und durch den Bindestrich bekommst du eine login-shell, was dir die Umgebungsvariablen des Benutzers gibt, zu dem du wechselst (ohne Angabe ist das root)”.
    • “Der PATH, der bei su gesetzt wird, beinhaltet nicht mehr /sbin und /usr/sbin, wodurch einige Programme nicht mehr durch Kurzeingabe des Programmnamens erreichbar sind. Durch Langeingabe geht es aber weiterhin”.
  • Debian Forum "Default (Root) Passwort für Debian Live Installation...?", 2012.
  • Switch to “root”:

    sudo su -l
    sudo su --login

• You may also set a new root password:

  sudo passwd root

• Ubuntu:
  • The Geek Stuff "Ubuntu Tips: How To Enable Root User ( Super User ) in Ubuntu".
• Techmint "How to Fix 'Username is not in the sudoers file. This incident will be reported” in Ubuntu' - This does not work for me.

• man7 "umount".
• man8 "umount".
• Xinix Wiki.
  • Xinix Wiki "Linux mount und umount".

• Archive.org "Debian Tutorials 'Reset your root Password on your Debian Machine'" → Modify Debian Linux boot menu by adding “init=/bin/bash” as additional boot parameter to ”/vmlinuz-2.6.18-5-486”.
• With my current Debian 12.0 system, the line looks like this

  linux /boot/vmlinuz6.1.0-37-amd64 root:UUD=XXXXXXXXXXXXXXXXXXX ro quiet
  

• Ask Ubuntu "Authentication token manipulation error" → “mount -rw -o remount /”.