Misc UNIX and Linux tricks for the desktop user and administrator.

[caption id="attachment_5999" align="alignleft" width="300"]TRON Legacy UNIX login to an sh prompt. TRON Legacy UNIX login to an sh prompt.[/caption]

Uptime. this is a useful command for finding out how long a Linux system has been running for. it also displays the load average over 1.5 and 15 minute intervals.

deep-thought ~ # uptime
21:45:32 up 32 min, 3 users, load average: 1.88, 1.45, 1.08

The w command will show the users that are logged into your Linux system and where they are logged in.

deep-thought ~ # w
22:04:39 up 51 min, 2 users, load average: 0.82, 0.76, 0.88
USER TTY FROM LOGIN@ IDLE JCPU PCPU WHAT
homer tty7 :0 21:14 51:08 22:12 0.07s gdm-session-worker [pam/gdm-password]
homer pts/0 :0.0 22:03 7.00s 0.28s 0.34s mate-terminal

To stop a service on a Linux system use the service command. This is used to stop and start services easily.

deep-thought ~ # service apache2 stop
* Stopping web server apache2 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName
... waiting

And this is how to start the service on Linux.

deep-thought ~ # service apache2 start
* Starting web server apache2 apache2: Could not reliably determine the server's fully qualified domain name, using 127.0.1.1 for ServerName

The free command is used to show how much free memory there is on your system. A very useful command indeed.

deep-thought ~ # free
total used free shared buffers cached
Mem: 6043416 4419804 1623612 0 862984 2024672
-/+ buffers/cache: 1532148 4511268
Swap: 15885300 0 15885300

This is the command the systems administrator used in the movie TRON Legacy. Here I am looking for a certain process ID. This also shows the processes running under the mate-terminal process.

deep-thought ~ # ps -ef | grep 7378
homer 7378 3406 0 22:03 ? 00:00:01 mate-terminal
homer 7384 7378 0 22:03 ? 00:00:00 gnome-pty-helper
homer 7385 7378 0 22:03 pts/0 00:00:00 zsh
root 7742 7505 0 22:29 pts/0 00:00:00 grep --colour=auto 7378
[caption id="attachment_6000" align="alignright" width="300"]TRON Legacy Encom UNIX machine. TRON Legacy Encom UNIX machine.[/caption]

The who am i command displays the name of your user and what tty you are logged in on.

deep-thought ~ # who am i
homer    pts/0        2013-07-18 22:03 (:0.0)

Using the find command to seek out a specific file in a folder.

deep-thought Desktop # find /home/homer/Desktop -name "snow*"
/home/homer/Desktop/snowden.jpg
/home/homer/Desktop/snowden.png

The lsof command lists all open files. Here I am listing all files that are opened by the mate-terminal process.

bash 10:40:38 Thu Jul 18 [homer@deep-thought $ lsof | grep mate-terminal
mate-term 7378           homer  txt       REG               8,97     313824 6030129 /usr/bin/mate-terminal
mate-term 7378           homer  mem       REG               8,97      61757  267120 /usr/share/locale/en_AU/LC_MESSAGES/mate-terminal.mo
gdbus     7378 7382      homer  txt       REG               8,97     313824 6030129 /usr/bin/mate-terminal
gdbus     7378 7382      homer  mem       REG               8,97      61757  267120 /usr/share/locale/en_AU/LC_MESSAGES/mate-terminal.mo
dconf     7378 7383      homer  txt       REG               8,97     313824 6030129 /usr/bin/mate-terminal
dconf     7378 7383      homer  mem       REG               8,97      61757  267120 /usr/share/locale/en_AU/LC_MESSAGES/mate-terminal.mo
gmain     7378 7386      homer  txt       REG               8,97     313824 6030129 /usr/bin/mate-terminal
gmain     7378 7386      homer  mem       REG               8,97      61757  267120 /usr/share/locale/en_AU/LC_MESSAGES/mate-terminal.mo

This is how to show the last reboot time on your Linux desktop or server machine.

bash 10:45:18 Thu Jul 18 [homer@deep-thought $ last reboot | head -n 1
reboot   system boot  3.8.0-25-generic Thu Jul 18 21:13 - 22:45  (01:31)

if you want to create many folders at once with the bash shell, then use this command.

bash 10:49:37 Thu Jul 18 [homer@deep-thought $ mkdir a b c d e f g

This is a very useful tip, how to only list directories with the ls command using the Linux command prompt. A very useful tip indeed.

bash 10:49:37 Thu Jul 18 [homer@deep-thought $ ls -ld */
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm a/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm b/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm c/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm d/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm e/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm f/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 10:49 pm g/
drwxrwxr-x 2 homer homer 4.0K  18-07-13 09:15 pm networking/
drwxr-xr-x 4 homer homer 4.0K  18-07-13 09:15 pm Site/

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