For example, add user jerry to groups ftp, www_data:

useradd -G ftp,www_data jerry

====== Shorthand at the Command Prompt ====== -

1. - / - root directory
2. -
3. -
4. - ./ - current directory
5. -
6. -
7. - ./command_name - run a command in the current directory when the current directory is not on the path
8. -
9. -
10. - ../ - parent directory
11. -
12. -
13. - ~ - home directory
14. -
15. -
16. - $ - typical prompt when logged in as ordinary user
17. -
18. -
19. - # - typical prompt when logged in as root or superuser
20. -
21. -
22. - ! - repeat specified command
23. -
24. -
25. - !! - repeat previous command
26. -
27. -
28. - ^^ - repeat previous command with substitution
29. -
30. -
31. - & - run a program in background mode
32. -
33. -
34. - [Tab][Tab] - prints a list of all available commands. This is just an example of autocomplete with no restriction on the first letter.
35. -
36. -
37. - x[Tab][Tab] - prints a list of all available completions for a command, where the beginning is ``x''
38. -
39. -
40. - [Alt][Ctrl][F1] - switch to the first virtual text console
41. -
42. -
43. - [Alt][Ctrl][Fn] - switch to the nth virtual text console. Typically, there are six on a Linux PC system.
44. -
45. -
46. - [Alt][Ctrl][F7] - switch to the first GUI console, if there is one running. If the graphical console freezes, one can switch to a nongraphical console, kill the process that is giving problems, and switch back to the graphical console using this shortcut.
47. -
48. -
49. - [ArrowUp] - scroll through the command history (in bash)
50. -
51. -
52. - [Shift][PageUp] - scroll terminal output up. This also works at the login prompt, so you can scroll through your boot messages.
53. -
54. -
55. - [Shift][PageDown] - scroll terminal output down
56. -
57. -
58. - [Ctrl][Alt][+] - switch to next X server resolution (if the server is set up for more than one resolution)
59. -
60. -
61. - [Ctrl][Alt][-] - change to previous X server resolution
62. -
63. -
64. - [Ctrl][Alt][BkSpc] - kill the current X server. Used when normal exit is not possible.
65. -
66. -
67. - [Ctrl][Alt][Del] - shut down the system and reboot
68. -
69. -
70. - [Ctrl]c - kill the current process
71. -
72. -
73. - [Ctrl]d - logout from the current terminal
74. -
75. -
76. - [Ctrl]s - stop transfer to current terminal
77. -
78. -
79. - [Ctrl]q - resume transfer to current terminal. This should be tried if the terminal stops responding.
80. -
81. -
82. - [Ctrl]z - send current process to the background
83. -
84. -
85. - reset - restore a terminal to its default settings
86. -
87. -
88. - [Leftmousebutton] - Hold down left mouse button and drag to highlight text. Releasing the button copies the region to the text buffer under X and (if gpm is installed) in console mode.
89. -
90. -
91. - [Middlemousebutton] - Copies text from the text buffer and inserts it at the cursor location. With a two-button mouse, click on both buttons simultaneously. It is necessary for three-button emulation to be enabled, either under gpm or in XF86Config.
92. - - Ordered List Item