Linked Questions

14
votes
2answers
6k views

Why does dd from /dev/urandom stops early? [duplicate]

On my current Linux system (Debian Jessie amd64), I'm getting different behavior for dd using /dev/urandom (/dev/random behavior is properly documented). If I naively want 1G of random data: $ dd if=/...
10
votes
1answer
1k views

Different size of file from /dev/zero and /dev/urandom [duplicate]

I am tring to create random 1G test file via dd command. dd status=progress if=/dev/zero of=/tmp/testfile.zer bs=100M count=10 dd status=progress if=/dev/urandom of=/tmp/testfile1.ran bs=100M count=...
2
votes
1answer
1k views

dd shows a random number of records in/out [duplicate]

I'm writing some images back to block devices, with dd, and getting very strange output I've never seen before. # xz -dc goren.img.xz | dd bs=1M of=/dev/storage2/goren 35+2475166 records in 35+...
78
votes
3answers
65k views

When to use /dev/random vs /dev/urandom

Should I use /dev/random or /dev/urandom? In which situations would I prefer one over the other?
60
votes
2answers
14k views

When is dd suitable for copying data? (or, when are read() and write() partial)

Short version: In what circumstances is dd safe to use for copying data, safe meaning that there is no risk of corruption due to a partial read or write? Long version — preamble: dd is often used to ...
10
votes
2answers
2k views

dd command bs option at end of disk

If I were to use the dd command as follows: dd if=/dev/zero of=/dev/sdX bs=16M What happens at the end of the disk if it is not an exact multiple of 16M? Does that mean the last remaining portion ...
4
votes
4answers
2k 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/...
4
votes
3answers
1k views

How do I DD over the network to an external HD?

I'm trying to clone a hard drive on my raspberry pi which is on the same network to an external harddrive of the computer I'm currently on. However I'm having issues piping the command correctly. I've ...
2
votes
1answer
2k views

Dirty in /proc/meminfo for dd

I read from here that the below command gives me the amount of data that needs to be written to the disk. grep ^Dirty /proc/meminfo It particularly says Ever ask yourself "How much data would be ...
5
votes
1answer
649 views

measure amount of data read from /dev/random

background I have written a collection of bash scripts (most of them in German only yet but if you are interested; download the archive not the single scripts) which help users create high-quality ...