How to use /dev/(u)random
How can I use /dev/(u)random on Ubuntu or any *nix sistems?
I tried this but it says permission denied.
Note : I also tried as root.
/dev/(u)random
sudo /dev/(u)random
sudo -s; /dev/(u)random
kernel bash
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
add a comment |
How can I use /dev/(u)random on Ubuntu or any *nix sistems?
I tried this but it says permission denied.
Note : I also tried as root.
/dev/(u)random
sudo /dev/(u)random
sudo -s; /dev/(u)random
kernel bash
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
1
Please notice that these commands should be used only, when you really need high quality random data, typically in order to create good passwords. Otherwise there are more light-weight alternatives, for example the shell environment 'variable'RANDOMto create random positive integer numbers:echo $RANDOM, and the programshufto generate random permutations, for example play in random order from a playlist.
– sudodus
Apr 18 '18 at 20:31
add a comment |
How can I use /dev/(u)random on Ubuntu or any *nix sistems?
I tried this but it says permission denied.
Note : I also tried as root.
/dev/(u)random
sudo /dev/(u)random
sudo -s; /dev/(u)random
kernel bash
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
How can I use /dev/(u)random on Ubuntu or any *nix sistems?
I tried this but it says permission denied.
Note : I also tried as root.
/dev/(u)random
sudo /dev/(u)random
sudo -s; /dev/(u)random
kernel bash
kernel bash
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
edited May 10 '15 at 4:34
Volker Siegel
8,91043349
8,91043349
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
asked Sep 23 '12 at 19:26
Caner Korkmaz
123116
123116
1
Please notice that these commands should be used only, when you really need high quality random data, typically in order to create good passwords. Otherwise there are more light-weight alternatives, for example the shell environment 'variable'RANDOMto create random positive integer numbers:echo $RANDOM, and the programshufto generate random permutations, for example play in random order from a playlist.
– sudodus
Apr 18 '18 at 20:31
add a comment |
1
Please notice that these commands should be used only, when you really need high quality random data, typically in order to create good passwords. Otherwise there are more light-weight alternatives, for example the shell environment 'variable'RANDOMto create random positive integer numbers:echo $RANDOM, and the programshufto generate random permutations, for example play in random order from a playlist.
– sudodus
Apr 18 '18 at 20:31
1
1
Please notice that these commands should be used only, when you really need high quality random data, typically in order to create good passwords. Otherwise there are more light-weight alternatives, for example the shell environment 'variable'
RANDOM to create random positive integer numbers: echo $RANDOM, and the program shuf to generate random permutations, for example play in random order from a playlist.– sudodus
Apr 18 '18 at 20:31
Please notice that these commands should be used only, when you really need high quality random data, typically in order to create good passwords. Otherwise there are more light-weight alternatives, for example the shell environment 'variable'
RANDOM to create random positive integer numbers: echo $RANDOM, and the program shuf to generate random permutations, for example play in random order from a playlist.– sudodus
Apr 18 '18 at 20:31
add a comment |
4 Answers
4
active
oldest
votes
It's a file like device, so you can do things like cat it or copy from it. For instance:
dd if=/dev/urandom of=~/urandom_test count=4 bs=1024
Creates a file containing 4K of random bytes.
cat /dev/urandom > ~/urandom_test2
Will continue to write random bytes to that file until you hit Ctrl-C. Don't do this on a low performing system...
head -30 /dev/urandom > ~/urandom_test3
Will write 30 lines of random bytes
answered Sep 23 '12 at 19:31
aychedee
4,87731513
1
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
4
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
1
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
1
Well.. that really depends on your definition of a line. My definition isbytes terminated by a n. What's yours?head -30 /dev/urandomwill give you 30 lines of random bytes. The length of those lines will certainly be random. Try runningwc -lon your output file if you aren't convinced.
– aychedee
May 11 '15 at 12:37
|
show 2 more comments
Get random bytes
If you need a certain number of random bytes, read that number of bytes from /dev/urandom.
It is a "special file" that is made to be like a file to read random numbers from.
Using cat to read from /dev/urandom is a bad idea, because it will try to read /dev/urandom to the end - but it does not end.
You can use head. But take care to read by byte, not by line - because lines would be randomly separated by random newline bytes.
So, to read 30 random bytes into a file random.bytes, use:
head -c 30 /dev/urandom > random.bytes
You can read from it as a normal user.
Leave alone /dev/random
Normally, you want to use /dev/urandom, not /dev/random.
The problem is that /dev/random is hard to use in the right way - and easy to use in a wrong way. Using it wrong works at first, but creates strange - even random - performance problems later. Sometimes.
When you use /dev/urandom, it makes use of /dev/random internally, taking care of the tricky parts.
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
add a comment |
If you want to just read it with recognized numbers you can do
od -d /dev/random
answered Apr 18 '18 at 20:15
Seraf
1313
add a comment |
I personally use this for generating tokens:
dd if=/dev/urandom count=1 bs=128 | sha512sum
answered Dec 28 '18 at 0:54
Farsheed
1615
add a comment |
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4 Answers
4
active
oldest
votes
4 Answers
4
active
oldest
votes
active
oldest
votes
active
oldest
votes
It's a file like device, so you can do things like cat it or copy from it. For instance:
dd if=/dev/urandom of=~/urandom_test count=4 bs=1024
Creates a file containing 4K of random bytes.
cat /dev/urandom > ~/urandom_test2
Will continue to write random bytes to that file until you hit Ctrl-C. Don't do this on a low performing system...
head -30 /dev/urandom > ~/urandom_test3
Will write 30 lines of random bytes
answered Sep 23 '12 at 19:31
aychedee
4,87731513
1
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
4
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
1
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
1
Well.. that really depends on your definition of a line. My definition isbytes terminated by a n. What's yours?head -30 /dev/urandomwill give you 30 lines of random bytes. The length of those lines will certainly be random. Try runningwc -lon your output file if you aren't convinced.
– aychedee
May 11 '15 at 12:37
|
show 2 more comments
It's a file like device, so you can do things like cat it or copy from it. For instance:
dd if=/dev/urandom of=~/urandom_test count=4 bs=1024
Creates a file containing 4K of random bytes.
cat /dev/urandom > ~/urandom_test2
Will continue to write random bytes to that file until you hit Ctrl-C. Don't do this on a low performing system...
head -30 /dev/urandom > ~/urandom_test3
Will write 30 lines of random bytes
answered Sep 23 '12 at 19:31
aychedee
4,87731513
1
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
4
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
1
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
1
Well.. that really depends on your definition of a line. My definition isbytes terminated by a n. What's yours?head -30 /dev/urandomwill give you 30 lines of random bytes. The length of those lines will certainly be random. Try runningwc -lon your output file if you aren't convinced.
– aychedee
May 11 '15 at 12:37
|
show 2 more comments
It's a file like device, so you can do things like cat it or copy from it. For instance:
dd if=/dev/urandom of=~/urandom_test count=4 bs=1024
Creates a file containing 4K of random bytes.
cat /dev/urandom > ~/urandom_test2
Will continue to write random bytes to that file until you hit Ctrl-C. Don't do this on a low performing system...
head -30 /dev/urandom > ~/urandom_test3
Will write 30 lines of random bytes
answered Sep 23 '12 at 19:31
aychedee
4,87731513
It's a file like device, so you can do things like cat it or copy from it. For instance:
dd if=/dev/urandom of=~/urandom_test count=4 bs=1024
Creates a file containing 4K of random bytes.
cat /dev/urandom > ~/urandom_test2
Will continue to write random bytes to that file until you hit Ctrl-C. Don't do this on a low performing system...
head -30 /dev/urandom > ~/urandom_test3
Will write 30 lines of random bytes
answered Sep 23 '12 at 19:31
aychedee
4,87731513
edited Sep 23 '12 at 19:52
answered Sep 23 '12 at 19:31
aychedee
4,87731513
answered Sep 23 '12 at 19:31
aychedee
4,87731513
answered Sep 23 '12 at 19:31
aychedee
4,87731513
4,87731513
1
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
4
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
1
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
1
Well.. that really depends on your definition of a line. My definition isbytes terminated by a n. What's yours?head -30 /dev/urandomwill give you 30 lines of random bytes. The length of those lines will certainly be random. Try runningwc -lon your output file if you aren't convinced.
– aychedee
May 11 '15 at 12:37
|
show 2 more comments
1
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
4
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
1
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
1
Well.. that really depends on your definition of a line. My definition isbytes terminated by a n. What's yours?head -30 /dev/urandomwill give you 30 lines of random bytes. The length of those lines will certainly be random. Try runningwc -lon your output file if you aren't convinced.
– aychedee
May 11 '15 at 12:37
1
1
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
Feel free to upvote then!
– aychedee
Sep 23 '12 at 19:36
4
4
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
I would if my rep > 15
– Caner Korkmaz
Sep 23 '12 at 19:38
1
1
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Note : Don't do cat /dev/urandom > ~/urandom_test2 on low-performance systems -> that freezes the system
– Caner Korkmaz
Sep 23 '12 at 19:44
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
Ah, true. I'll change my second example.
– aychedee
Sep 23 '12 at 19:50
1
1
Well.. that really depends on your definition of a line. My definition is
bytes terminated by a n. What's yours? head -30 /dev/urandom will give you 30 lines of random bytes. The length of those lines will certainly be random. Try running wc -l on your output file if you aren't convinced.– aychedee
May 11 '15 at 12:37
Well.. that really depends on your definition of a line. My definition is
bytes terminated by a n. What's yours? head -30 /dev/urandom will give you 30 lines of random bytes. The length of those lines will certainly be random. Try running wc -l on your output file if you aren't convinced.– aychedee
May 11 '15 at 12:37
|
show 2 more comments
Get random bytes
If you need a certain number of random bytes, read that number of bytes from /dev/urandom.
It is a "special file" that is made to be like a file to read random numbers from.
Using cat to read from /dev/urandom is a bad idea, because it will try to read /dev/urandom to the end - but it does not end.
You can use head. But take care to read by byte, not by line - because lines would be randomly separated by random newline bytes.
So, to read 30 random bytes into a file random.bytes, use:
head -c 30 /dev/urandom > random.bytes
You can read from it as a normal user.
Leave alone /dev/random
Normally, you want to use /dev/urandom, not /dev/random.
The problem is that /dev/random is hard to use in the right way - and easy to use in a wrong way. Using it wrong works at first, but creates strange - even random - performance problems later. Sometimes.
When you use /dev/urandom, it makes use of /dev/random internally, taking care of the tricky parts.
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
add a comment |
Get random bytes
If you need a certain number of random bytes, read that number of bytes from /dev/urandom.
It is a "special file" that is made to be like a file to read random numbers from.
Using cat to read from /dev/urandom is a bad idea, because it will try to read /dev/urandom to the end - but it does not end.
You can use head. But take care to read by byte, not by line - because lines would be randomly separated by random newline bytes.
So, to read 30 random bytes into a file random.bytes, use:
head -c 30 /dev/urandom > random.bytes
You can read from it as a normal user.
Leave alone /dev/random
Normally, you want to use /dev/urandom, not /dev/random.
The problem is that /dev/random is hard to use in the right way - and easy to use in a wrong way. Using it wrong works at first, but creates strange - even random - performance problems later. Sometimes.
When you use /dev/urandom, it makes use of /dev/random internally, taking care of the tricky parts.
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
add a comment |
Get random bytes
If you need a certain number of random bytes, read that number of bytes from /dev/urandom.
It is a "special file" that is made to be like a file to read random numbers from.
Using cat to read from /dev/urandom is a bad idea, because it will try to read /dev/urandom to the end - but it does not end.
You can use head. But take care to read by byte, not by line - because lines would be randomly separated by random newline bytes.
So, to read 30 random bytes into a file random.bytes, use:
head -c 30 /dev/urandom > random.bytes
You can read from it as a normal user.
Leave alone /dev/random
Normally, you want to use /dev/urandom, not /dev/random.
The problem is that /dev/random is hard to use in the right way - and easy to use in a wrong way. Using it wrong works at first, but creates strange - even random - performance problems later. Sometimes.
When you use /dev/urandom, it makes use of /dev/random internally, taking care of the tricky parts.
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
Get random bytes
If you need a certain number of random bytes, read that number of bytes from /dev/urandom.
It is a "special file" that is made to be like a file to read random numbers from.
Using cat to read from /dev/urandom is a bad idea, because it will try to read /dev/urandom to the end - but it does not end.
You can use head. But take care to read by byte, not by line - because lines would be randomly separated by random newline bytes.
So, to read 30 random bytes into a file random.bytes, use:
head -c 30 /dev/urandom > random.bytes
You can read from it as a normal user.
Leave alone /dev/random
Normally, you want to use /dev/urandom, not /dev/random.
The problem is that /dev/random is hard to use in the right way - and easy to use in a wrong way. Using it wrong works at first, but creates strange - even random - performance problems later. Sometimes.
When you use /dev/urandom, it makes use of /dev/random internally, taking care of the tricky parts.
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
answered May 10 '15 at 4:59
Volker Siegel
8,91043349
8,91043349
add a comment |
add a comment |
If you want to just read it with recognized numbers you can do
od -d /dev/random
answered Apr 18 '18 at 20:15
Seraf
1313
add a comment |
If you want to just read it with recognized numbers you can do
od -d /dev/random
answered Apr 18 '18 at 20:15
Seraf
1313
add a comment |
If you want to just read it with recognized numbers you can do
od -d /dev/random
answered Apr 18 '18 at 20:15
Seraf
1313
If you want to just read it with recognized numbers you can do
od -d /dev/random
answered Apr 18 '18 at 20:15
Seraf
1313
answered Apr 18 '18 at 20:15
Seraf
1313
answered Apr 18 '18 at 20:15
Seraf
1313
answered Apr 18 '18 at 20:15
Seraf
1313
1313
add a comment |
add a comment |
I personally use this for generating tokens:
dd if=/dev/urandom count=1 bs=128 | sha512sum
answered Dec 28 '18 at 0:54
Farsheed
1615
add a comment |
I personally use this for generating tokens:
dd if=/dev/urandom count=1 bs=128 | sha512sum
answered Dec 28 '18 at 0:54
Farsheed
1615
add a comment |
I personally use this for generating tokens:
dd if=/dev/urandom count=1 bs=128 | sha512sum
answered Dec 28 '18 at 0:54
Farsheed
1615
I personally use this for generating tokens:
dd if=/dev/urandom count=1 bs=128 | sha512sum
answered Dec 28 '18 at 0:54
Farsheed
1615
answered Dec 28 '18 at 0:54
Farsheed
1615
answered Dec 28 '18 at 0:54
Farsheed
1615
answered Dec 28 '18 at 0:54
Farsheed
1615
1615
add a comment |
add a comment |
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1
Please notice that these commands should be used only, when you really need high quality random data, typically in order to create good passwords. Otherwise there are more light-weight alternatives, for example the shell environment 'variable'
RANDOMto create random positive integer numbers:echo $RANDOM, and the programshufto generate random permutations, for example play in random order from a playlist.– sudodus
Apr 18 '18 at 20:31