====== [hemmerling] Debian Linux 2/4 ======
Related page:
  *[[debian.html|Debian Linux 1/4]].
  *[[debian03.html|Debian Linux 3/4]].
  *[[debian04.html|Debian Linux 4/4]].
  *[[unix.html|Unix 1/12]].
  *[[unix02.html|Unix 2/12 - Linux & BSD Distributions]].
  *[[linuxskills.html|Linux Skills & Skill Certification]].
===== General Linux / Unix Commands =====
==== chmod ====
=== Command Examples ===
=== Resources ===
  *[[http://www.computerhope.com/unix/uchmod.htm|Computer Hope. Free computer help since 1998 "Linux chmod command"]].
  *[[http://www.ionos.com/digitalguide/server/know-how/allocating-directory-rights-with-chmod/|IONOS "What is chmod?"]] - "chmod help & examples".
  *[[http://unix.stackexchange.com/questions/639438/whats-the-difference-between-chmod-ax-and-chmod-x|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.
  *[[http://unix.stackexchange.com/questions/429421/why-does-chmod-w-not-give-write-permission-to-othero|StackExchange "Why does chmod +w not give write permission to other(o)"]].
  *[[http://wiki.ubuntuusers.de/chmod/|ubuntuusers - Fragen ist menschlich!]].
  *[[http://www.warp.dev/terminus/chmod-x|Warp "Chmod +X"]] - "Understanding Chmod +X - Making Files Executable".
    *To make a script executable by every user on the system:<code>
$ chmod +x script.sh</code>
==== su, "su -" and sudo ====
=== PATH on Debian Linux ===
  *Default user:<code>
$printenv
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
</code>
  *su ( root ):<code>
$su
$printenv
PATH=/usr/local/bin:/usr/bin:/bin:/usr/local/games:/usr/games
</code>
  *su - ( root ):<code>
$su -
$printenv
PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin
</code>
=== Add a user "USERNAME" to the "sudo" group, as first and only user ===
<code>
$su -
Password:
# $apt install sudo
$usermod -aG sudo USERNAME
$getent group sudo
</code>
=== Alternative ( unnecessary complex ? ) Instructions for Debian 10.7 ===
  *Add the USERNAME ( of the user as which you are logged in ) to the group "sudoers".
    -( Open a terminal ).
    -su root  
    -( Input root password. root is already member of the group "sudoers" :-) ).
    -apt-get install sudo -y
    -//su -//
    -adduser **username** sudo
    -//logout//
    -chmod  0440  /etc/sudoers
    -exit
    -<del>sudo reboot</del>
    -( Input root password ).
    -( reboot manually if "sudo reboot" doesn't work )
=== How to become "root" on Debian Live Installation ===
  *"sudo su" & lowercase ( "-L" ) or lowercase ( "- -Login" ):<code>
sudo su -l
sudo su --login
</code>
=== Resources ===
  *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<code>
Username Is Not In The Sudoers File. This Incident Will Be Reported</code>
    *Especially, the "GDebi Package Installer" quits without error message after entering the right password :-(.
  *[[http://en.wikipedia.org/wiki/Su_%28Unix%29|EN.Wikipedia "su (Unix)"]], [[http://de.wikipedia.org/wiki/Su_%28Unix%29|DE.Wikipedia "su (Unix)"]].
  *[[http://en.wikipedia.org/wiki/Sudo|EN.Wikipedia "sudo"]], [[http://de.wikipedia.org/wiki/Sudo|DE.Wikipedia "sudo"]].
  *[[http://wiki.debian.org/sudo/|Debian Wiki "sudo"]].
  *Debian:
    *[[http://www.reddit.com/r/linuxquestions/comments/pcfjo6/bash_usermod_command_not_found_in_latest_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".
    *[[http://www.cloudpanel.io/tutorial/how-to-add-user-to-sudoers-in-debian/|CloudPanel "How to Add User to Sudoers in Debian"]].
    *[[http://unix.stackexchange.com/questions/179954/username-is-not-in-the-sudoers-file-this-incident-will-be-reported|StackExchange "Username is not in the sudoers file. This incident will be reported"]].
    *[[http://unix.stackexchange.com/questions/565665/bash-adduser-command-not-found-debian-buster|StackExchange "bash: adduser: command not found [Debian Buster]"]].
    *[[http://www.techrepublic.com/article/how-to-install-sudo-on-a-debian-minimal-server/|TechRepublic "How to install sudo on a Debian minimal server"]].
    *[[http://debianforum.de/forum/viewtopic.php?t=175456|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".
    *[[http://www.debianforum.de/forum/viewtopic.php?t=137945|Debian Forum "Default (Root) Passwort für Debian Live Installation...?"]], 2012.
    *Switch to "root":<code>
sudo su -l
sudo su --login</code>
   *You may also set a new root password:<code>
sudo passwd root</code>
  *Ubuntu:
    *[[http://www.thegeekstuff.com/2009/09/ubuntu-tips-how-to-login-using-su-command-su-gives-authentication-failure-error-message/|The Geek Stuff "Ubuntu Tips: How To Enable Root User ( Super User ) in Ubuntu"]]. 
   *[[http://www.tecmint.com/fix-user-is-not-in-the-sudoers-file-the-incident-will-be-reported-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.
==== mount & umount ====
  *[[http://www.man7.org/linux/man-pages/man8/umount.8.html|man7 "umount"]].
  *[[http://www.man7.org/linux/man-pages/man8/mount.8.html|man8 "umount"]].
  *[[http://www.xinux.net/|Xinix Wiki]].
    *[[http://www.xinux.net/index.php/Linux_mount_und_umount|Xinix Wiki "Linux mount und umount"]].

===== Untested =====
==== Forgotten root Password ====
  *[[http://web.archive.org/web/*/http://www.debiantutorials.org/reset-root-password-debian-gnulinux-etch-286.html|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<code>
linux /boot/vmlinuz6.1.0-37-amd64 root:UUD=XXXXXXXXXXXXXXXXXXX ro quiet
</code>
  *[[http://www.askubuntu.com/questions/91188/authentication-token-manipulation-error|Ask Ubuntu "Authentication token manipulation error"]] -> "mount -rw -o remount /".
{{tag>linux debian}}
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