Linux-101-Hacks

Table of Contents
Introduction.............................................................7
Foreword.................................................................8
Version....................................................................8
Chapter 1: Powerful CD Command Hacks.........................9
Hack 1. Use CDPATH to define the base directory for cd command...9
Hack 2. Use cd alias to navigate up the directory effectively.........10
Hack 3. Perform mkdir and cd using a single command................13
Hack 4. Use “cd -” to toggle between the last two directories.......14
Hack 5. Use dirs, pushd and popd to manipulate directory stack.....14
Hack6. Use “shopt -s cdspell” to automatically correct mistyped directorynames on cd.........................................................17
Chapter 2: Date Manipulation.......................................18
Hack 7. Set System Date and Time..........................................18
Hack 8. Set Hardware Date and Time.......................................19
Hack 9. Display Current Date and Time in a Specific Format..........19
Hack 10. Display Past Date and Time.......................................21
Hack 11. Display Future Date and Time....................................22
Chapter 3: SSH Client Commands..................................24
Hack 12. Identify SSH Client Version........................................24
Hack 13. Login to Remote Host using SSH.................................24
Hack 14. Debug SSH Client Session..........................................26
Hack 15. Toggle SSH Session using SSH Escape Character..............27
Hack 16. SSH Session Statistics using SSH Escape Character...........29
Chapter 4: Essential Linux Commands............................31
Hack 17. Grep Command......................................................31
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Linux 101 Hacks

Hack 18. Find Command.......................................................33
Hack 19. Suppress Standard Output and Error Message.................35
Hack 20. Join Command.......................................................35
Hack 21. Change the Case.....................................................36
Hack 22. Xargs Command......................................................37
Hack 23. Sort Command.......................................................38
Hack 24. Uniq Command.......................................................41
Hack 25. Cut Command........................................................42
Hack 26. Stat Command.......................................................43
Hack 27. Diff Command........................................................44
Hack 28. Display total connect time of users.............................45
Chapter 5: PS1, PS2, PS3, PS4 and PROMPT_COMMAND.......47
Hack 29. PS1 - Default Interaction Prompt................................47
Hack 30. PS2 - Continuation Interactive Prompt.........................48
Hack 31. PS3 - Prompt used by “select” inside shell script............49
Hack 32. PS4 - Used by “set -x” to prefix tracing output..............50
Hack 33. PROMPT_COMMAND.................................................52
Chapter 6: Colorful and Functional Shell Prompt Using PS1.53
Hack34. Display username, hostname and basename of directory in theprompt.......................................................................53
Hack 35. Display current time in the prompt.............................53
Hack 36. Display output of any command in the prompt...............54
Hack 37. Change foreground color of the prompt........................55
Hack 38. Change background color of the prompt.......................56
Hack 39. Display multiple colors in the prompt..........................57
Hack 40. Change the prompt color using tput............................58
Hack41. Create your own prompt using the available codes for PS1variable............................................................................59
Hack 42. Use bash shell function inside PS1 variable...................61
Hack 43. Use shell script inside PS1 variable.............................61
Chapter 7: Archive and Compression..............................63
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Linux 101 Hacks

Hack 44. Zip command basics................................................63
Hack 45. Advanced compression using zip command...................65
Hack 46. Password Protection of Zip files.................................66
Hack 47. Validate a zip archive..............................................66
Hack 48. Tar Command Basics................................................67
Hack 49. Combine gzip, bzip2 with tar.....................................68
Chapter 8: Command Line History.................................70
Hack 50. Display TIMESTAMP in history using HISTTIMEFORMAT......70
Hack 51. Search the history using Control+R.............................70
Hack52. Repeat previous command quickly using 4 differentmethods......................................................................................72
Hack 53. Execute a specific command from history.....................72
Hack54. Execute previous command that starts with a specificword......................................................................................73
Hack55. Control the total number of lines in the history usingHISTSIZE...........................................................................73
Hack 56. Change the history file name using HISTFILE..................73
Hack57. Eliminate the continuous repeated entry from history usingHISTCONTROL....................................................................74
Hack58. Erase duplicates across the whole history usingHISTCONTROL....................................................................75
Hack59. Force history not to remember a particular command usingHISTCONTROL....................................................................76
Hack 60. Clear all the previous history using option -c.................76
Hack 61. Substitute words from history commands.....................77
Hack 62. Substitute a specific argument for a specific command....77
Hack 63. Disable the usage of history using HISTSIZE...................78
Hack64. Ignore specific commands from the history usingHISTIGNORE......................................................................................78
Chapter 9: System Administration Tasks.........................80
Hack 65. Partition using fdisk................................................80
Hack 66. Format a partition using mke2fsk...............................82
Hack 67. Mount the partition.................................................84
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Linux 101 Hacks

Hack 68. Fine tune the partition using tune2fs..........................84
Hack 69. Create a swap file system.........................................86
Hack 70. Create a new user...................................................87
Hack 71. Create a new group and assign to an user.....................88
Hack 72. Setup SSH passwordless login in OpenSSH.....................89
Hack 73. Use ssh-copy-id along with ssh-agent...........................91
Hack 74. Crontab................................................................92
Hack 75. Safe Reboot Of Linux Using Magic SysRq Key..................94
Chapter 10: Apachectl and Httpd Examples.....................97
Hack 76. Pass different httpd.conf filename to apachectl.............97
Hack77. Use a temporary DocumentRoot without modifyinghttpd.conf........................................................................98
Hack 78. Increase the Log Level temporarily.............................99
Hack 79. Display the modules inside Apache.............................100
Hack 80. Show all accepted directives inside httpd.conf..............101
Hack 81. Validate the httpd.conf after making changes...............101
Hack 82. Display the httpd build parameters............................102
Hack 83. Load a specific module only on demand......................103
Chapter 11: Bash Scripting........................................105
Hack 84. Execution Sequence of .bash_* files...........................105
Hack 85. How to generate random number in bash shell..............106
Hack 86. Debug a shell script................................................107
Hack 87. Quoting...............................................................108
Hack 88. Read data file fields inside a shell script......................110
Chapter 12: System Monitoring and Performance............112
Hack 89. Free command......................................................112
Hack 90. Top Command.......................................................113
Hack 91. Ps Command.........................................................116
Hack 92. Df Command.........................................................118
Hack 93. Kill Command.......................................................119
Hack 94. Du Command........................................................121
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Linux 101 Hacks

Hack 95. lsof commands......................................................121
Hack 96. Sar Command.......................................................124
Hack 97. vmstat Command...................................................126
Hack 98. Netstat Command..................................................128
Hack 99. Sysctl Command....................................................130
Hack 100. Nice Command....................................................132
Hack 101. Renice Command.................................................134
12 Amazing and Essential Linux Books..........................136
Extended Reading...................................................139
Your Feedback and Support.......................................140
Subscribe to TGS...............................................................140
Contact TGS.....................................................................140

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