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13 Aug 16:41

What the inside of a pneumatic transport system looks like

by Brian Benchoff


While most of us are familiar with pneumatic transport systems by their use at drive-up bank windows, these systems are also commonly found in hospitals ferrying samples around. When [Aidan] was in the hospital, he asked how this series of tubes routed samples from many different floors to the lab and back again. Well, give him an old tube to play around with and he’ll eventually come up with a way to record the inside of one of these pneumatic tubes, giving some insight into how this system actually works.

When asked, a tech that uses this system on a daily basis described it as a very basic physical Ethernet that sucks and blows through rotary junctions and physical hubs to route packets to different areas of the building. [Aidan] wanted to record a tube’s travels, so he wired up a small HD camera, a bunch of LEDs, and a few batteries. Sending this recording sample container revealed some of how this pneumatic system works; the containers will travel forward and stop before reversing through one of the rotary switches. You can check out the flight of the container in the video below.

Of course there are other glimpses of how stuff travels through the unseen world of getting from point A to point B. Here’s a time lapse camera going on a trip via DHL just for kicks.

Filed under: digital cameras hacks
05 Aug 21:10

xkcd: The Mother of All Suspicious Files

From xkcd:

The Mother of All Suspicious Files


Updated to add: explainer.

On 05/08/13 At 09:07 AM

05 Aug 20:50

Comic for August 5, 2013

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05 Aug 20:49

Comic for August 4, 2013

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05 Aug 17:31

That's The Sound of Dreams Dying

That's The Sound of Dreams Dying

Submitted by: Unknown

31 Jul 07:41

After spending 5 minutes on getting remote code execution on a client's web server


by MaXe

28 Jul 19:50

simplenomad: 13 yrs ago we were "paranoid" w/personal mail servers, encrypted chat, etc. Next time listen to us.

13 yrs ago we were "paranoid" w/personal mail servers, encrypted chat, etc. Next time listen to us.
22 Jul 12:41

15 Command Line Tools for Monitoring Linux Systems

by Stefan Sinca

Do you need to monitor your Linux server’s performance? Most Linux distributions come equipped with many built-in monitoring tools. These tools allow you to retrieve information about system activities, and can be used to find possible causes for your server’s performance issues.

The commands discussed in this article are some of the most basic commands when it comes to system analysis and debugging server issues, such as discovering disk, CPU, memory and network bottlenecks.

1 - top – The Process Activity Command

The top command provides a dynamic, real-time view of the running system (i.e. actual process activity). By default, it displays the most CPU-intensive tasks running on the server and updates the list every five seconds.

Commonly Used Hot Keys

Most Linux distributions come equipped with many built-in monitoring tools.

There are several useful hot keys used with the top command:

  • t — toggles summary information off and on.
  • m — toggles memory information off and on.
  • A — sorts the display by top consumers of various system resources. This is useful for quickly identifying performance-hungry tasks.
  • f — enters an interactive configuration screen for top. It’s helpful for configuring top for a specific task.
  • o — enables you to interactively select the order of the displayed fields.
  • r — issues the renice command.
  • k — issues the kill command.
  • z — toggles between color and monochrome.

2 - vmstat – System Activity, Hardware and System Information

The vmstat command reports virtual memory statistics: processes, memory, paging, block IO, traps and cpu activity.


# vmstat 3

Sample output:

    procs -----------memory---------- ---swap-- -----io---- --system-- -----cpu------
    r b swpd free buff cache si so bi bo in cs us sy id wa st
    0 0 0 2540988 522188 5130400 0 0 2 32 4 2 4 1 96 0 0
    1 0 0 2540988 522188 5130400 0 0 0 720 1199 665 1 0 99 0 0
    0 0 0 2540956 522188 5130400 0 0 0 0 1151 1569 4 1 95 0 0
    0 0 0 2540956 522188 5130500 0 0 0 6 1117 439 1 0 99 0 0
    0 0 0 2540940 522188 5130512 0 0 0 536 1189 932 1 0 98 0 0
    0 0 0 2538444 522188 5130588 0 0 0 0 1187 1417 4 1 96 0 0
    0 0 0 2490060 522188 5130640 0 0 0 18 1253 1123 5 1 94 0 0 

Display memory utilization slabinfo with the following command:

# vmstat -m

And you can retrieve information about active and inactive memory pages with:

# vmstat -a

3 - w – Logged In Users

The w command displays information about the currently logged in users and their processes. Its syntax is:

    # w [user]

Running this command gives you output similar to the following:

    17:58:47 up 5 days, 20:28, 2 users, load average: 0.36, 0.26, 0.24
    root pts/0 14:55 5.00s 0.04s 0.02s vim /etc/resolv.conf
    root pts/1 17:43 0.00s 0.03s 0.00s w

4 - uptime – System Uptime

The uptime command not only displays the amount of time the server has been running, but the current time, how many users are currently logged on and the system load average for the past 1, 5, and 15 minutes.

# uptime

Its output will look similar to:

11:57:40 up 96 days, 17:23,  0 users,  load average: 1.17, 1.15, 1.14

5 - ps – The Processes

The ps command reports a snapshot of the current processes. To select all processes, use the -A or -e option.

# ps -A

Running this command on your system will provide similar results to the following:

     PID TTY          TIME CMD
    6538 ?        00:00:00 anytermd
    6543 pts/4    00:00:00 bash
    6855 pts/4    00:00:00 ps

To show long format output, add “l” at the end:

# ps -Al

Turn on extra-full mode to show the command line arguments passed to the processes by adding “F”:

# ps -AlF

Add an “H” to see threads (LWP and NLWP):

# ps -AlFH

To see threads after processes, add “m”:

# ps -AlLm

Or print a process tree:

    # ps -ejH
    # ps axjf
    # pstree

Display only the process IDs of lighttpd:

# ps -C lighttpd -o pid=


# pgrep lighttpd

You can also find the top ten processes using the most CPU with:

# ps -auxf | sort -nr -k 3 | head -10

6 - free – Memory Usage

The free command displays the total amount of physical and swap memory in the system, as well as the buffers used by the kernel.

# free

This simple command’s output looks like:

    total used free shared buffers cached
    Mem: 12302896 9739664 2563232 0 523124 5154740
    -/+ buffers/cache: 4061800 8241096
    Swap: 1052248 0 1052248

7 - iostat – Average CPU Load and Disk Activity

The iostat command reports CPU and input/output statistics for devices, partitions and network filesystems (NFS).

# iostat

And the obligatory sample output:

    Linux 3.4.5-hardened-v3 (tryit)         12/14/12        _i686_  (1 CPU)
    avg-cpu:  %user   %nice  %system %iowait  %steal  %idle
               2.47    6.52    2.54    1.57    0.00   86.90
    Device:            tps    kB_read/s    kB_wrtn/s    kB_read    kB_wrtn

8 - sar – Collect and Report System Activity

The sar command collects, reports and saves system activity information. To see the network counter, enter:

# sar -n DEV | more

To display the network counters from the 24th:

# sar -n DEV -f /var/log/sa/sa24 | more

You can also display real time usage using sar:

# sar 4 5

Sample output:

    Linux 3.4.5-hardened-v3 (tryit)         12/14/12        _i686_  (1 CPU)
    12:45:25        CPU     %user     %nice   %system   %iowait    %steal     %idle
    12:45:29        all      0.43     19.70      1.07      0.00      0.00     78.80
    12:45:33        all      0.43     19.35      1.51      1.51      0.00     77.20
    12:45:37        all      0.43     18.49      1.94      0.00      0.00     79.14
    12:45:41        all      0.43     19.02      2.14      0.00      0.00     78.42
    12:45:45        all      0.65     18.49      2.37      0.00      0.00     78.49
    Average:        all      0.47     19.01      1.80      0.30      0.00     78.41

9 - mpstat – Multi-processor Usage

The mpstat command displays each available processor’s activities, with processor 0 being the first. Use the following command to display the average CPU utilization per processor:

# mpstat -P ALL

And this is the output:

    Linux 3.4.5-hardened-v3 (tryit)         12/14/12        _i686_  (1 CPU)
    12:47:46     CPU    %usr   %nice    %sys %iowait    %irq   %soft  %steal  %guest    %idle
    12:47:46     all    2.47    6.52    1.48    1.57    0.00    1.06    0.00    0.00    86.90
    12:47:46       0    2.47    6.52    1.48    1.57    0.00    1.06    0.00    0.00    86.90

10 - pmap – Process Memory Usage

The pmap command reports the memory map of a process. Use this command to find the causes of memory bottlenecks.

# pmap -d PID

To display process memory information for pid # 47394, enter:

# pmap -d 47394

Sample output:

    47394: /usr/bin/php-cgi
    Address Kbytes Mode Offset Device Mapping
    0000000000400000 2584 r-x-- 0000000000000000 008:00002 php-cgi
    0000000000886000 140 rw--- 0000000000286000 008:00002 php-cgi
    00000000008a9000 52 rw--- 00000000008a9000 000:00000 [ anon ]
    0000000000aa8000 76 rw--- 00000000002a8000 008:00002 php-cgi
    000000000f678000 1980 rw--- 000000000f678000 000:00000 [ anon ]
    000000314a600000 112 r-x-- 0000000000000000 008:00002
    000000314a81b000 4 r---- 000000000001b000 008:00002
    000000314a81c000 4 rw--- 000000000001c000 008:00002
    000000314aa00000 1328 r-x-- 0000000000000000 008:00002
    000000314ab4c000 2048 ----- 000000000014c000 008:00002
    00002af8d48fd000 4 rw--- 0000000000006000 008:00002
    00002af8d490c000 40 r-x-- 0000000000000000 008:00002
    00002af8d4916000 2044 ----- 000000000000a000 008:00002
    00002af8d4b15000 4 r---- 0000000000009000 008:00002
    00002af8d4b16000 4 rw--- 000000000000a000 008:00002
    00002af8d4b17000 768000 rw-s- 0000000000000000 000:00009 zero (deleted)
    00007fffc95fe000 84 rw--- 00007ffffffea000 000:00000 [ stack ]
    ffffffffff600000 8192 ----- 0000000000000000 000:00000 [ anon ]
    mapped: 933712K writeable/private: 4304K shared: 768000K

The last line is very important:

mapped: 933712K total amount of memory mapped to files
writeable/private: 4304K the amount of private address space
shared: 768000K the amount of address space this process is sharing with others

11 - netstat – Network Statistics

The netstat command displays both incoming and outgoing network connections, routing tables and a number of network interface statistics. It is available on Unix, Unix-like systems, and Windows NT-based operating systems.

 # netstat 

12 - iptraf – Real-time Network Statistics

The iptraf command is an colorful, interactive IP LAN monitor. It is an ncurses-based IP LAN monitor that generates various network statistics including TCP info, UDP counts, ICMP and OSPF information, Ethernet load info, node stats, IP checksum errors and more. It can provide the following info in easy to read format:

  • Network traffic statistics by TCP connection.
  • IP traffic statistics by network interface.
  • Network traffic statistics by protocol.
  • Network traffic statistics by TCP/UDP port and packet size.
  • Network traffic statistics by Layer2 address.

13 - tcpdump – Detailed Network Traffic Analysis

The tcpdump is a simple command that dumps a network’s traffic. You need, however, a good understanding of the TCP/IP protocol in order to use this tool. For example, to display traffic info about DNS, enter:

 # tcpdump -i eth1 'udp port 53'

To display all IPv4 HTTP packets from port 80 (i.e. print only packets that contain data; not, for example, SYN abd FIN packets and ACK-only packets), enter:

 # tcpdump 'tcp port 80 and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)'

To display all HTTP sessions to

# tcpdump -ni eth0 'dst and tcp and port http'

14 - strace – System Calls

The strace command traces system calls and signals. This is useful for debugging the webserver and other server problems.

The following command runs strace against /bin/foo and captures its output to output.txt:

 # strace -o output.txt /bin/foo

15 - /proc – Various Kernel Statistics

The /proc file system provides detailed information about various hardware devices and other Linux kernel information. Common /proc examples are:

    # cat /proc/cpuinfo
    # cat /proc/meminfo
    # cat /proc/zoneinfo
    # cat /proc/mounts 


And there you have it: fifteen useful commands that let you monitor different aspects of your Linux system. Naturally, these commands are only a small subset of the many that Linux provides. But for day to day operations, they are usually enough.

Have a favorite command? Let’s keep the conversation going within the comments area.

22 Jul 12:18

Never and ever and ever and ever and ever....

22 Jul 12:17

Cannot Unsee

Cannot Unsee

Lol by: Unknown (via Tumblr)

22 Jul 11:00

The new guy downloads netcat.exe from some random site he found via Google

by @cl0pen

21 Jul 05:14

thegrugq: “@DrVonBraun: Great photo of yesterday's MUOS-2 satellite launch from an airplane cockpit:”< ha! Cloud boner.

“@DrVonBraun: Great photo of yesterday's MUOS-2 satellite launch from an airplane cockpit:”
20 Jul 17:23

41414141: "Jesus, can you turn off your caps lock?" "NO I AM CODING IN FORTRAN"

"Jesus, can you turn off your caps lock?" "NO I AM CODING IN FORTRAN"
20 Jul 17:22

41414141: Best GIF of all time:

Best GIF of all time:
20 Jul 17:19

mubix: #ATM

20 Jul 17:13

taviso: Funny, a post on full-disclosure broke the gmane archive.…

Funny, a post on full-disclosure broke the gmane archive.…
20 Jul 12:43

When you realize everything is in the same /16

When you realise

by Rattle

20 Jul 09:26

Comic for July 18, 2013

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20 Jul 09:24

Comic for July 15, 2013

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20 Jul 09:24

Comic for July 14, 2013

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20 Jul 09:22

Comic for July 9, 2013

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20 Jul 09:18

Comic for July 2, 2013

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20 Jul 08:38

Bash Redirections Cheat Sheet

by Peteris Krumins

Hey guys! A few weeks ago I wrote an article called All About Bash Redirections. It explains all the possible bash redirections with illustrations. I thought it would be a great idea to make a cheat sheet that summarizes all these redirections. So I did.

Here is the bash redirections cheat sheet:

Download PDF | Download PNG | Download TXT | Download TEX

If you want to learn how each one of these redirections work, read my article All About Bash Redirections!

Found a mistake or want to contribute to this cheat sheet? Fork it on github!


PS. I've created a dozen different cheat sheets. Take a look at my other cheat sheets about awk, ed, sed, perl, screen, more bash, gnu coreutils, util-linux, and many others.

19 Jul 12:15

Suddenly Banana

Suddenly Banana

Submitted by: Unknown (via Knowyourmeme)

Tagged: suddenly , banana , Cats , funny
19 Jul 12:15

The Mystery is Solved

The Mystery is Solved

Submitted by: Unknown

19 Jul 08:52

Retrotechtacular: Bell Labs introduces a thing called ‘UNIX’

by Brian Benchoff


Modern operating systems may seem baroque in their complexity, but nearly every one of them  - except for Windows, natch – are based on the idea of simplicity and modularity. This is the lesson that UNIX taught us, explained perfectly in a little film from Bell Labs in 1982 starring giants of computation, [Dennis Ritchie], [Ken Thompson], [Brian Kernighan], and others.

At the time this film was made, UNIX had been around for about 10 years. In that time, it had moved far from an OS cloistered in giant mainframes attached to teletypes to slightly smaller minicomputers wired up to video terminals. Yes, smallish computers like the Apple II and the VIC-20 were around by this time, but they were toys compared to the hulking racks inside Bell Labs.

The film explains the core concept of UNIX by demonstrating modularity with a great example by [Brian Kernighan]. He took a short passage from a paper he wrote and found spelling errors by piping his paper though different commands from the shell. First the words in the paper were separated line by line, made lowercase, and sorted alphabetically. All the unique words were extracted from this list, and compared to a dictionary. A spell checker in one line of code, brought to you by the power of UNIX.

Filed under: Software Development, software hacks
12 Jul 19:05

The Surreal Illustrations of Tebe Interesno

by John Farrier


The digital works of Russian artist Tebe Interesno are either stunning, funny or both. I especially like the submarine image, which reminds me of the anime series Space Battleship Yamato.

Link (Translation) -via Colossal

12 Jul 17:19

all the tools you need to be anonymous or encrypted online whatever you do

by belsec, researcher for

it is one of those big organized lists that are not that easy for the newbies and dummies - you still…

12 Jul 16:45

That was not supposed to work

by sharhalakis

image by Constantine

12 Jul 16:38

Stepping a long loop when debugging

by sharhalakis

by tkrugg