UNIX random devices and utilities

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5
votes
1answer
59 views

Random image generator

I am generating random data and trying to convert it to a PNG image using : head -c 1MB < /dev/urandom | hexdump -e '16/1 "_x%02X"' | sed 's/_/\\/g; s/\\x //g; s/.*/ "&"/' | tr -d "\"" | ...
0
votes
1answer
56 views

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))
0
votes
1answer
17 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
votes
1answer
38 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 ...
1
vote
1answer
57 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 .... train/m/...
13
votes
2answers
227 views

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

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 ...
0
votes
2answers
43 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
3
votes
3answers
137 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 ...
2
votes
2answers
57 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 ...
8
votes
1answer
276 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 ...
1
vote
4answers
50 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 $...
1
vote
2answers
68 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 ...
1
vote
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 ...
0
votes
1answer
85 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 ...
1
vote
2answers
53 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 ...
3
votes
4answers
155 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
2
votes
3answers
147 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
votes
1answer
183 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 ...
28
votes
8answers
9k 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 ...
3
votes
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 ...
0
votes
1answer
26 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
votes
3answers
448 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
votes
3answers
114 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 (...
4
votes
1answer
194 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
votes
2answers
337 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 ...
1
vote
2answers
135 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
votes
2answers
217 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
vote
3answers
86 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 3314.55,d4:0b:1a:...
0
votes
3answers
78 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 ...
6
votes
5answers
921 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
votes
3answers
460 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
votes
2answers
188 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 ...
3
votes
1answer
3k 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 (...
5
votes
1answer
479 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. ...
4
votes
4answers
676 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 /dev/...
2
votes
3answers
216 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
votes
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 ...
3
votes
2answers
396 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
votes
1answer
976 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
votes
1answer
118 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> &...
1
vote
2answers
134 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
votes
1answer
349 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 "...
4
votes
1answer
662 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
votes
1answer
949 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 ...
2
votes
2answers
278 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
votes
2answers
823 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?
4
votes
1answer
279 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 ...
0
votes
2answers
165 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 "...
4
votes
2answers
543 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
votes
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 ...