Debian GNU/Linux help

Useful commands

• Important for installations in the console
  For selection fields press the space bar to mark fields.
• Search in files
  git grep "[SEARCH]"
• Unzip files
  tar -xzvf *.gz
tar -jxvf *.bz2
• Show current Linux version
  lsb_release -a
• Update short form
  apt update && apt upgrade -y && apt full-upgrade -y && apt autoremove -y
  The individual commands
  apt update
apt upgrade
apt full-upgrade === apt-get dist-upgrade
apt autoremove
• Service systems
  Which system does my operating system use? SysVInit or SystemD?
  ps -p 1
  SystemD, New
  systemctl status [SERVICE]
  SystemD, the path to the command is specified explicitly
  /bin/systemctl status [SERVICE]
  SysVInit, Deprecated
  /etc/init.d/[SERVICE] status
  SysVInit, service often associated with /etc/init.d/
service [SERVICE] status
• Service commands
  systemctl status [SERVICE]
systemctl start [SERVICE]
systemctl stop [SERVICE]
systemctl restart [SERVICE]
systemctl enable [SERVICE] (add to autostart)
  systemctl disable [SERVICE]

VirtualBox guest extension

1. Switch to root user
   su -
2. Update software
   apt update && apt upgrade -y && apt full-upgrade -y && apt autoremove -y
   Restart when a new Linux kernel has been installed.
3. Install packages for building kernel modules
   apt install build-essential module-assistant dkms
4. Preparation for creating kernel modules
   m-a prepare
5. Insert guest extension
   Devices -> insert guest additions ...
   Run (CD is mounted)
6. Install guest extension
   sh /media/cdrom0/VBoxLinuxAdditions.run
7. Check modules
   lsmod or grep -io vboxguest or xargs modinfo or grep -iw version
8. Only members of the vboxsf group have access to automatically integrated folders
   vboxsf = VirtualBox shared folder
   sudo adduser [USER] vboxsf
9. Restart -> Done

Users

• Show all users
  cat /etc/passwd | cut -d: -f1
• Switch to root user
  su -
• Create new user
  adduser [USER]
• Change user
  su [USER]
• Add user to group
  adduser [USER] [GROUP]
• Remove user from group
  deluser [USER] [GROUP]
• Show groups of the user
  groups [USER]
• List all groups
  groups
• Delete user
  deluser [USER] --remove-home --remove-all-files
• Delete group
  delgroup [GROUP]
visudo ([GROUP] ALL=(ALL:ALL) ALL -> Delete lines if any)
• Login as www-data
  su -s /bin/bash www-data (no password is set; www-data, to-www or auto-www)

Owners and Rights

• chown -R [USER]:[GROUP] [FOLDER/FILE]
• chmod -R 775 [FOLDER/FILE]
• chmod g+s

Symbolic (umask u=rwx,g=rx,o=)
u = User
g = Group
o = Other
Permissions
r = read
w = write
x = execute

Octal (umask 022)
0 = read, write and execute
1 = read and write
2 = read and execute
3 = read only
4 = write and execute
5 = write only
6 = execute only
7 = no permissions

Cron Jobs

• View root cron jobs
  crontab -l
• Cron jobs are saved here
  /etc/cron.*
• Software specific cron jobs
  /etc/cron.d
• Add cron job
  crontab -u [USERNAME] -e
crontab -u dreadyhead -e
  Select editor and insert job entry at the bottom.
• Control cron jobs
  crontab -u [USERNAME] -l
• Change cron job
  crontab -u [USERNAME] -e
• Delete cron job
  crontab -u [USERNAME] -r

TrueCrypt

1. Download package
   wget http://www.truecrypt.org/download/truecrypt-7.1a-linux-x86.tar.gz
wget http://www.truecrypt.org/download/truecrypt-7.1a-linux-x64.tar.gz
2. Unzip
   tar -xzvf truecrypt-7.1a-linux-x86.tar.gz
3. Install
   sudo ./truecrypt-7.1a-setup-x86
4. Uninstall
   sudo truecrypt-uninstall.sh
5. Execute
   truecrypt

Filezilla

• apt install filezilla

LFTP

• apt install lftp

Run *.sh file

• chmod +x [FILENAME]
• ./[FILENAME]

Convert line endings

DOS/Windows line break (CR LF), in Unix System (LF) convert end of line / line break.

• apt install dos2unix
• Now you can convert the line endings in both directions
  dos2unix [FILE]
unix2dos [FILE]
• Testing
  vi [FILE]
:x! to leave vi

JDK for NetBeans is already installed

• Testing
  java -version
• Folder
  /usr/lib/jvm/java-8-openjdk-amd64

Compare two folders

• diff -rq [FOLDER1] [FOLDER2]
• -r = Recursively compare any subdirectories found.
• -q = Output only whether files differ.

Symbolic Link

• ln -s [FOLDER/FILE] [SYMLINKNAME]

Uninstall a package

• dpkg --list
• Check dependencies
  apt-cache depends [PACKAGE]
• Remove package
  apt remove [PACKAGE]
• Remove package and its configuration files
  apt purge [PACKAGE]