UNIX random devices and utilities

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4answers
38 views

Rename files randomly but without repetition

Suppose i have a folder with a lot of file names some very strange and nonsense I want to rename it like File-1 File-2 File-3 .. I have tried this(echo is for tryng) for name in *; do echo mv ...
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2answers
29 views

Generate unique numbers RANDOM function OS X

I am creating a random generator based from a number array list. However, I would like it to be unique so that random number cannot be used again. I have tried creating a 'USED' array list which will ...
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1answer
32 views

Password Generator not working OS X

I am creating a Password Generator using 4 Arrays (Lower Case, Upper Case, Symbol and Number) with the RANDOM function. Basically I will generate a random number and then apply it to each of those ...
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1answer
49 views

How to create a dynamic greeting?

Recently made the switch to Linux/command line, and I'm having trouble creating a dynamic greeting for terminal out of a list of predetermined possibilities. I tried the following, but it appears as ...
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2answers
38 views

Appending Echo [Password Generator]

I am creating a password generator however I am not get the passwords to append properly. Here is my script i="0" while [ $i -lt 5 ] do echo -n '#' >> passwords.txt && openssl rand ...
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4answers
100 views

How do I create a text file (1 gigabyte) containg random characters with UTF-8 character encoding?

The following command does not use UTF-8: head -c 1M </dev/urandom >myfile.txt
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3answers
95 views

Random number generation in Solaris?

What is the best way to generate random numbers in Solaris? I can not seem to find a good answer for this. Most results do not work in my environment. There is a variable or command RAND that seems ...
1
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1answer
66 views

How to check if reading from /dev/random will block

I have found information that /proc/sys/kernel//random/entropy_avail indicates number of bits available in /dev/random. I wanted to check whether the next reading from /dev/random will block and my ...
21
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8answers
3k views

How to generate a random string?

I would like to generate a random string (e.g. passwords, user names, etc.). It should be possible to specify the needed length (e.g. 13 chars). What tools can I use? (For security and privacy ...
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5answers
54 views

How do I exchange names for a large amount of files in a folder?

I want to randomize the names for about 350 files in a folder, but I want to have all the names that the files had originally. What I mean is I want All of the names in my folder randomized from the ...
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1answer
22 views

Generating files of varying variability?

I have used /dev/zero and /dev/random to generate files of certain size. However, is there a way to control variability of generated files? I would like to create few files that would have same ...
6
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3answers
351 views

Print random lines respecting the order of the source file

I have a large text file (~500K lines) with short sentences (couple of words long). Additionally, there is some XML markup in most of the lines. Finally, the text file has been sorted before the ...
2
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3answers
86 views

Duplicate a file with random probability

I have a directly full of images and I am trying to put together a script/command that will randomly copy (with some probability) the image to a location with a random name at that destination ...
3
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1answer
114 views

Shuffle two parallel text files

I have two sentence-aligned parallel corpora (text files) with about 50 mil words. (from the Europarl corpus -> parallel translation of legal documents). I'd now like to shuffle the lines of the two ...
3
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2answers
141 views

Is it bad to have a low entropy in /dev/random?

I wonder whether for the average Linux user it is considered as bad -from a point of view of security or any other relevant viewpoints- to have no or almost no entropy left in /dev/random. Edit: I ...
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2answers
69 views

Randomly copy certain amount of certain file type from one directory into another

Sometimes I have a folder full of jpg's and I need to randomly choose 8 or so of them. How could I automate this so my account randomly chooses 8 jpg's from the folder and copies them to another ...
2
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2answers
190 views

How to generate a random string in a profile alias?

I have an alias in my server's /etc/profile which generates a random directory on command, like this: alias rdir="mkdir -p ./`cat /dev/random | tr -cd 'a-z0-9' | head -c 8`/" But it turns out this ...
1
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3answers
80 views

Random sampling and outputting the largest value

I have a fairly large data set ~500 million rows. The data set looks like below. Col 1 is float number, col 2 is mac id(device id) 1616.93,ac:22:0b:a6:22:c3 2872.32,c0:bd:d1:36:bb:49 ...
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3answers
75 views

How to achieve “continuos randomness”?

With RANDOM%xone gets a set of discrete results. How can I achieve following scenario?: Inside a for loop, I'd like to let a bash script execute command A in 33.33% of all loops and else execute ...
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5answers
764 views

Sources of Entropy for Linux

Let's say I want a gigabyte or so of random data from /dev/random, suitable for a one-time pad (so /dev/urandom is out.) How do I seed my /dev/random with enough entropy to do this? I am looking for ...
3
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2answers
292 views

How can I shuffle pages from a pdf file in a random order?

I would like to shuffle the pages of a pdf document in a random order. How can this be done?
4
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2answers
86 views

Decreasing or emptying the entropy pool?

I work with virtual machines a lot, and they seem to generally be low on entropy (no mouse or other entropy-generating inputs). A bug with my software has surfaced, and I think it's due to running out ...
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0answers
29 views

adapt this yates-fisher code for a random generator

I am trying to make my version of a random number generator that doesn't leave bash scripting language. Starting with a yates-fisher shuffle, i am trying to use this as the starting point...and go ...
3
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1answer
2k views

Debian Jessie - Random freezes

I have a fresh installation of Debian Jessie, with Cinnamon and Gnome. I run it on a decent computer with the following specs: Athlon II x3, 6GB DDR2, 2GB SWAP (swapiness minimum), 600GB SATA HDD ...
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1answer
453 views

How to copy a file several times into randomly choosen paths within the filesystem?

I have a filesystem and a special file foo. I would like the script to choose several times (5,10 or 100) random paths to folders within this filesystem and to copy the file foo into each of them. ...
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4answers
573 views

How to fill a file with a stream from /dev/urandom with a specified number of lines ?

I am trying to fill a file with a sequence of random 0 and 1s with a user-defined number of lines and number of characters per line. the first step is to get a random stream of 0 and 1s: cat ...
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3answers
174 views

gpg key generation on Tails live cd - why so quick?

I just used gpg2 --gen-key to generate a 2048 bit RSA key pair on an OS running on a live cd (Tails). This happened much faster than I expected. When I have done this before on a regular machine it ...
3
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1answer
51 views

How random is the pseudo random number generators on live boot disks? Is there a way to seed it?

I know that random number generators on computers are only pseudo-random, but are the PRNGs on Live Boot USB or DVDs even less random? Is there a way to seed them after booting? Specifically curious ...
3
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2answers
275 views

How to quickly generate (insecure) GPG keys?

I'd like to automate generating at least two GPG keys for testing and demonstration purposes in a virtual machine. Because of this context I want to make sure the key generation is fast, ideally not ...
2
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1answer
750 views

Changing the hostname on a Linux Mint desktop to a random value at boot time

When changing the hostname to a random set of alphanumeric characters on a machine running Linux Mint(17.1 Rebecca, Cinnamon 64-bit) I encounter some problems. The following script changes the ...
0
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1answer
106 views

php shell_exec() + /dev/hwrng: no output

I have this PHP script: <?php $od = shell_exec('od /dev/hwrng --address-radix=n --read-bytes=4 --format=u4'); ?> <html> <head> <title>hwrng</title> </head> ...
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2answers
94 views

Creating a device similar to /dev/random from a script

I am writing a program for which I will create a script to generate test data in a specific format. How can I create a /dev/myprogram device that would work similar to /dev/random (preferably in ...
2
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1answer
267 views

Low(?) entropy available on Arch Linux?

I just had some problems to get Pidgin with OTR running, because Pidgin hung on every attempt to generate my private key. This rather old blog post pointed me into the right direction (or rather ...
2
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1answer
385 views

What entropy sources are used by the Linux kernel?

man 4 random has a very vague description of Linux kernel entropy sources: The random number generator gathers environmental noise from device drivers and other sources into an entropy ...
2
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1answer
654 views

rngd - multiple instances from init script

On Ubuntu >=12.04, what is the most correct/prettiest way to get rngd to run in multiple instances using an init script? The current one only accepts one random source, so multiple instances are ...
1
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2answers
189 views

Randomize arguments ( that hold color codes) from an array

I have the array (shown below) with arguments that hold color codes. The intended purpose of my script is to randomize those arguments when the user inputs "scriptname randoms Text" so that every time ...
4
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2answers
659 views

random permutation of lines of text

If I have a file with following content: 0001 0002 0003 0004 0132 0137 0138 0141 How can I get a random permutation of them in bash?
3
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1answer
145 views

What is the correct available entropy on UNIX systems?

I have three questions related to entropy on UNIX systems: I check entropy on Linux using: cat /proc/sys/kernel/random/entropy_avail. Is this the standard place with information about available ...
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2answers
145 views

check two partitions by selecting random files and running sha1 hashes on two files of each partition

A previous answer to a post mentions to run sha1 hashes on an images of a dd drive clone image. Another answer to that post suggests mounting the dd image an then compare if the sha1 hashes of ...
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2answers
436 views

Generating file with ASCII numbers using /dev/urandom?

How can I generate 10 MB files from /dev/urandom filled with: ASCII 1s and 0s ASCII numbers between 0 and 9
3
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1answer
1k views

How to debug random reboots, with no kernel panic, of an embedded system?

I have two aValue RPC-10W1 embedded systems that reboots by themselves after 1-2 hours. Facts: The board will reboot within a time span of 1 to 2½ hours. The issue is present on two identical ...
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2answers
2k views

Why writing to /dev/random does not make parallel reading from /dev/random faster?

Typically reading from /dev/random produces 100-500 bytes and blocks, waiting for an entropy to be collected. Why doesn't writing information to /dev/random by other processes speed up reading? ...
16
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8answers
29k views

Generate random numbers in specific range

After googling a bit I couldn't find a simple way to use a shell command to generate a random decimal integer number included in a specific range, that is between a minimum and a maximum. I read ...
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2answers
2k views

Adding “random number entropy” for GPG keys?

In the following video: Linux HOWTO: Secure Your Data with PGP, Part 2, you are shown how to create a key pair with gpg. At about 1:50, the instructor says the following: While the key is being ...
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0answers
162 views

xdotool random/more natural delay?

For automated testing of some applications, I would like to emulate the users behaviour. I know I can user the xdotool type --delay option, but I would like a more natural delay. The easiest thing ...
2
votes
4answers
763 views

Overwriting a Disk

Should I use: find / -type f -exec shred -uvz -nX or just good old dd if=/dev/urandom of=/dev/sda Is one faster or more secure than the other?
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1answer
215 views

/usr/bin/random using a lot of CPU

Using QNX 6.4.1, there is a command called pidin times that shows information about processes. I think it means PID INformation. Among other things, you can see how much CPU a process has used since ...
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1answer
311 views

Can you explain the entropy estimate used in random.c

/dev/random uses the timings of kernel interupts to add to the entropy pool. The amount of entropy in the pool is tracked in a variable named entropy_count. Here is the relevant snippet of code from ...
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4answers
4k views

Create random data with dd and get “partial read warning”. Is the data after the warning now really random?

I create a 1TB file with random data with dd if=/dev/urandom of=file bs=1M count=1000000. Now I check with kill -SIGUSR1 <PID> the progress and get the following: 691581+0 Datensätze ein ...
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2answers
2k views

RSA 2048 keypair generation: via openssl 0.5s via gpg 30s, why the difference?

RSA 2048 keypair generation: via openssl 0.5s via gpg 30s, why the difference There are several programs which can gerate RSA public/private keypairs GnuPG/OpenPGP for instance has a wizzard being ...