1. Schedule a queue to run at 9am on March 1st. Note: Ctrl-d to save and exit.
$ at 9am March 1
2. Schedule a queue to run after 5 minutes.
$ at now +5 minutes
3. Check any jobs pending to run, same as at -l .
$ atq
4. Empty out a file.
$ cat /dev/null > /path/to/file
5. Change directory, see also pushd and popd.
$ cd
6. List run level information for the service type.
$ chkconfig --list
7. Change owner recursively.
$ chown -R : /path/to/directory
8. Change shell.
$ chsh
9. Scan recursively for viruses.
$ clamscan -r
10. Compare two files.
$ cmp file1 file2
11. Copy keeping the directory structure.
$ cp --parent /source/path /destination/path
12. Copy keeping the permissions of the user.
$ cp -p
13. Copy recursive.
$ cp -r
14. Copy without shell aliasing.
$ \cp
15. List crontab for user.
$ crontab -u -l
16. Check current date and time.
$ date
17. Set current date and time, may need to set the hardware clock to the system time too, `man hwclock`.
$ date -s 'Wed May 28 11:35:00 EST 2003'
18. Show disk free in human readable format.
$ df -h
19. Configure interface using DHCP protocol.
$ dhclient eth0
20. Find context differences between two files.
$ diff -c
21. Creating a patch file.
$ diff -Naur oldDir/oldFile newDir/newFile > new_patchFile
22. Kernel buffer
$ dmesg
23. Show disk used in human readable format.
$ du -h /path/to/directory
24. Find files larger than 10MB.
$ find /path/to/file -size +10000k
25. Find file permissions with setuids.
find / \( -perm -4000 -o -perm -2000 \) -exec ls -ldb {} \;>> /tmp/suids
26. Search for world writable files and directories.
$ find / -perm -002
27. Display information on free and used memory.
$ free
28. Grep on word boundaries.
grep -w
29. Count the number of mathces - similar to “wc -l”.
$ grep -c
30. Perform timings of device reads for benchmark and comparison purposes.
$ hdparm -t /dev/hda1
31. Set the hardware clock to the current system time.
$ hwclock --systohc
32. check the ip address
$ ifconfig
33. Add an ip address to eth0.
$ ifconfig eth0:x xxx.xxx.xxx.xxx
34. Install loadable kernel module. You can also use `modprobe` to do the same.
$ insmod
35. Displays information about your system’s CPU and I/O.
$ iostat [ interval [ count ] ]
36. List iptables firewall rules in numeric format.
$ iptables -L -n
37. HangUP process so it will re-read the config file.
$ killall -HUP
38. Install the boot loader and increase verborsity.
$ lilo -v -v
39. Query the boot map.
$ lilo -q
40. One time boot to the named kernel.
$ lilo -R
41. Create symbolic link to the target file or directory.
$ ln -s
42. Configure dynamic linker run-time bindings
$ ldconfig
43. List the IPs bound via Ensim
$ listaliases
44. Quickly search for indexed files. Run `updatedb` to update the indexed database.
$ locate
45. List files.
$ ls
46. List loaded kernel modules
$ lsmod
47. Create the access.db file database map for sendmail.
$ makemap hash /etc/mail/access.db < /etc/mail/access
48. Create/Make a new directory.
$ mkdir
49. Generate a random 128 character length password.
$ mkpasswd -l 128
50. Read in the contents of your mbox (or the specified file).
$ mail -f /var/mail/nameOfFile
51. Print the mail queue
$ mailq
52.Print the complete mail queue
$ mailstat /path/to/procmail/log
53. Description of the hierarchy directory structure of the system
$ man hier
54. Check the MD5 message digest.
$ md5sum
55. Mount points check.
$ mount
56. Provide information about your systems’ processor.
$ mpstat [ interval [ count ] ]
57.
$ ncftpget -R -u -p
hostname /local_dir /remote_dir
58.
$ netstat -a | grep -i listen
59. Will show you who is attached to what port.
$ netstat -anpe
60.
$ netstat -n
61. See which programs are listening on which port
$ netstat -lnp
62. Will show you what local TCP ports are open and what programs are running on them.
$ netstat -lntpe
63. Will show you what local UDP ports are open and what programs are running on them.
$ netstat -lnupe
64. Run a program with modified scheduling priority. (# range between -20 to +20, negative is higher priority)
$ nice -n # [command to nice]
65. Scan network
$ nmap -v hostname/ip
66. Patch and keep a backup
$ patch -p# -b < patch_file
67.
$ ps -ecaux
68. Turn off all quotas for users and groups, verbose mode
$ quotaoff -augv
69. Check quota for all users and groups interactively, do quotaoff first.
$ quotacheck -augmiv
70. Turn on all quotas for users and groups
$ quotaon -augv
71. Add host ip to route on a particular device.
$ route add -host xxx.xxx.xxx.xxx dev eth0:x
72.
$ rdate
73. Remove file
$ rm
74. Remove kernel module
$ rmmod
75. Display the routing table in numeric.
$ route -n
76.
$ rpm
77. Uninstall/erase package.
$ rpm -e
78. Erase without dependency check.
$ rpm -e --nodeps
79. List out installed rpms by date, latest on top.
$ rpm -qa --last | less
80. Rebuild rpm database.
$ rpm --rebuilddb
81. Find which package owns the file.
$ rpm -qf /path/to/file
$ rpm -q --whatprovides /path/to/file
82. Verify package.
$ rpm -V
or
$ rpm -Vf /path/to/file
83. Locate documentation for the package that owns the file.
$ rpm -qdf /path/to/file
84. Query information on package.
$ rpm -qip
85. Query files installed by package.
$ rpm -qlp
86. Gives list of files that will be installed/overwritten.
$ rpm -ql
87. Will show the scripts that will be executed.
$ rpm -q --scripts
88. Display system activity information
$ sar
89. Print a 0 padded sequence of numbers.
$ seq -w 1 10
90. Record eveything printed on your terminal screen.
$ script -a
Ctrl+D to exit out. `more ` to view.
91. Check the status of a service.
$ service status
92. Restart after shutdown and force fsck (fsck may take a while).
$ shutdown -rF now
93. Split a file into pieces with numeric suffixes, so it can be burnt to cds.
$ split -d -b 640k big_input_filename.gz piece_file_prefix.gz.
To piece it back you can `cat piece_file_prefix.gz.* > original.gz`
94. Determine if a network service binary is linked againt tcp wrapper, libwrap.a
$ strings -f | grep hosts_access
96. how to use tar
$ tar -cvzf fileName.tar.gz `find /file/path -mtime -1 ! -type d -print`
97.
$ tar -xvzpf fileName.tar.gz /path/to/file.txt
98. How to use tcpdump
$ tcpdump -i eth0 dst port 80 | more
99. System process status
$ top
100. View the full command line.
$ top -c
101. Create empty file of 0 byte
$ touch
102. Similar to `which` - shows full path to the command.
$ type
103. Check the limit of user
$ ulimit -a
104. Check the version of kernel running
$ uname -a
105. Update package profile with rhn
$ up2date -p
106. Install package via up2date.
$ up2date -i
107.
$ uptime
108.
$ usermod
109. Utility reports virtual memory statistics
$ vmstat [second interval] [no. of count]
110. Show who is logged on and what they are doing.
$ w
111. Periodically watch output of a command in full screen
$ watch ''
112. Run and generate the apache reports using webalizer
$ webalizer -c /path/to/webalizer.conf
113. Recursive download of a url, converting links, no parent.
$ wget -r -k -np
114. Mirror, convert links, backup original, dynamic to html and output a “logFile”.
$ wget -m -k -K -E -o [logFile]
115. Locate the binary, source, and manual page files for a command.
$ whereis
116. Shows the full path of command.
$ which
117. Show who is logged on.
$ who
118. Yum package updates
$ yum check-update -- check to see what updates are needed
$ yum info -- show basic information about a package
$ yum update -- update particular package
119. Control jobs:
$ Ctrl-z -- suspend foreground job
$ jobs -- list jobs
$ bg -- send job to background
$ fg -- bring job to foreground
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