Text Terminal on the Graphical Desktop

• A terminal emulator program emulates (simulates) a standalone terminal within a window on the desktop.
• By default, on GNOME desktop environments, the gnome-terminal application is used to emulate a text-mode terminal in a window. Other available terminal programs include:
  • xterm
  • rxvt
  • konsole (default on KDE)
  • terminator
• Most input lines entered at the shell prompt have three basic elements:
  • Command
  • Options
  • Arguments
  • Other elements (such as setting environment variables)

Virtual Terminals (GNOME Terminal)

• Virtual Terminals (VT) are console sessions that use the entire display and keyboard outside of a graphical environment;
• Such terminals are considered “virtual” because, although there can be multiple active terminals, only one terminal remains visible at a time.
• To switch between VTs, press CTRL-ALT-function key for the VT. For example, press CTRL-ALT-F6 for ‘VT 6’. Actually, you only have to press the ALT-F6 key combination if you are in a VT and want to switch to another VT.
• One virtual terminal (usually number one or seven) is reserved for the graphical environment, and text logins are enabled on the unused VTs. Ubuntu uses ‘VT 7’, but CentOS/RHEL and openSUSE use ‘VT 1’ for the graphical display.

Turning Off the Graphical Desktop

• For the newer systemd-based distributions, the display manager is run as a service, you can stop the GUI desktop with the systemctl utility and most distributions will also work with the telinit command, as in:

sudo systemctl stop <gdm|lightdm|kdm># ORsudo telinit 3sudo systemctl start <gdm|lightdm|kdm># ORsudo telinit 5

• On Ubuntu versions before 18.04 LTS, substitute lightdm for gdm.

sudo

• sudo allows users to run programs using the security privileges of another user, generally root (superuser).

su    # enter sudo mode# create the configuration file for 'student' under sudo modeecho "student ALL=(ALL) ALL" > /etc/sudoers.d/studentchmod 440 /etc/sudoers.d/student

Getting Help - man, apropos, -help, info and Others

• Manual: man [pages] Divided into chapters numbered 1 through 9:
  • User commands
  • Programming interfaces for kernel system calls
  • Programming interfaces to the C library
  • Special files such as device nodes and drivers
  • File formats
  • Miscellaneous
  • System administration commands

man lsman passwdman -k passwd       # -k: key word, will return section of a key wordman -k `^passwd$`man 5 passwd        # 5: the section returned by above commandman -f passwdman -a socket       # all pages with the given name in all chaptersapropos passwd      # equivalent to `man -k [pages]`apropos partitionwhat is passwd      # equivalent to `man -f [pages]`

• GNU info: The topic which you view in an info page is called a node.
  • n: Go to the next node
  • p: Go to the previous node
  • u: Move one node up in the index