UNIX random devices and utilities

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How does this equation gives numbers random between two values?

How does this equation gives random numbers between max and min divisible by divisibleBy echo $(((RANDOM%(max-min+divisibleBy))/divisibleBy*divisibleBy+min))
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2answers
184 views

What program(s) is(are) lowering my entropy pool level?

I've made a simple bash script that checks the entropy pool level in /dev/random. I realize that the way I do it, I lower it very slightly at each check (cat /proc/sys/kernel/random/entropy_avail) but ...
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1answer
15 views

KSH password generator

How to make sure the generated passwords contains all these special characters: ?!/=\? Currently I'm using: pwd_usr["$i"]=`cat /dev/urandom|tr -dc "a-zA-Z0-9-_\?\!\=\/\"|fold -w 15|head -n 1` But ...
2
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1answer
35 views

Split text file in random halves based on category

I have a text file that looks like this: n03250847/n03250847_0.JPEG n03250847 n03250847/n03250847_1.JPEG n03250847 ... n03250847/n03250847_499.JPEG n03250847 ... n03255030/n03255030_0.JPEG n03255030 ...
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1answer
56 views

Extract random sample of N lines based on pattern

I have a file formatted like this: train/t/temple/east_asia/00000025.jpg 94 train/t/temple/east_asia/00000865.jpg 94 ... train/s/swamp/00000560.jpg 92 train/s/swamp/00000935.jpg 92 .... ...
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2answers
39 views

How to pick a random element from the output of a command?

if I have sth. like echo 1 2 3 4 5 6 or echo man woman child what do I have to put behind the pipe to pick out one element of 1 2 3 4 5 6 or man woman child ? echo 1 2 3 4 5 6 | command 3
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3answers
107 views

Using /dev/random, /dev/urandom to generate random data

I'm looking for ways to use /dev/random (or /dev/urandom) from the command line. In particular, I'd like to know how to use such a stream as stdin to write streams of random numbers to stdout (one ...
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2answers
53 views

Would draining entropy make it easier to compromise a system? [duplicate]

Entropy is important for many security features like TCP sequence numbers and cryptographic key/parameter generation. My understanding is that the entropy pool is drained by an operation as simple as ...
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3answers
415 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?
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1answer
244 views

Is it wrong to link /dev/random to /dev/urandom on Linux?

I'm currently testing gpg --genkey on a Linux VM. Unfortunately, this software seems to rely on /dev/random to gather entropy and politely asks the user to manually type screens after screens of ...
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9answers
38k 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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49 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
21k views

How can I populate a file with random data?

How can I create a new file and fill it with 1 Gigabyte worth of random data? I need this to test some software. I would prefer to use /dev/random or /dev/urandom.
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2answers
60 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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4answers
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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 Datens├Ątze ein ...
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5answers
6k views

Fast Way to Randomize HD?

I've read about how to make hard drives secure for encryption, and one of the steps is to write random bits to the drive, in order to make the encrypted data indistinguishable from the rest of the ...
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1answer
35 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
77 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
52 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
141 views
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3answers
128 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 ...
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 ...
2
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1answer
135 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 ...
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3answers
11k views

Reading from /dev/random does not produce any data

I often use the command cat /dev/urandom | strings --bytes 1 | tr -d '\n\t ' | head --bytes 32 to generate pseudo-random passwords. This doesn't work with /dev/random. Specifically cat ...
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8answers
8k 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
61 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
24 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 ...
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3answers
112 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 ...
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3answers
425 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 ...
3
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2answers
283 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 ...
4
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1answer
178 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 ...
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2answers
105 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 ...
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2answers
209 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 ...
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4answers
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Why can't tr read from /dev/urandom on OSX?

A colleague suggested creating a random key via the following command: tr -dc A-Za-z0-9_\!\@\#\$\%\^\&\*\(\)-+= < /dev/urandom | head -c 32 | xargs It gave me the error: tr: Illegal byte ...
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3answers
85 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
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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
880 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 ...
4
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2answers
158 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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1answer
478 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
6k views

Tool for measuring entropy quality?

Is there a tool available for Linux systems that can measure the "quality" of entropy on the system? I know how to count the entropy: cat /proc/sys/kernel/random/entropy_avail And I know that some ...
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2answers
517 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
4
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4answers
657 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 ...
21
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4answers
7k views

Why does dd from /dev/random give different file sizes?

I am running the following command on an ubuntu system: dd if=/dev/random of=rand bs=1K count=2 However, every time I run it, I end up with a file of a different size. Why is this? How can I ...
2
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3answers
205 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 ...
2
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1answer
923 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 ...
3
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1answer
53 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 ...
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2answers
365 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 ...
0
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1answer
117 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
123 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
323 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 ...