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From: | Pádraig Brady |
Subject: | bug#12626: Bug?: dd limited to <2G read size (2G-8K) on 64 bit machine? |
Date: | Fri, 12 Oct 2012 10:14:13 +0100 |
User-agent: | Mozilla/5.0 (X11; Linux x86_64; rv:13.0) Gecko/20120615 Thunderbird/13.0.1 |
tag 12626 notabug stop On 10/12/2012 07:42 AM, Paul Eggert wrote:
On 10/11/2012 11:39 PM, Linda Walsh wrote:I'm not even getting error messages if I try to do 4G @ a timeThat's what dd is supposed to do. It requests 4 GB, the kernel gives it only 2 GB, so it goes with 2 GB. dd has always worked that way, and POSIX requires it to work that way.
As my mother would say, that's a lazy man's load. Please use a more reasonable buffer size. Also note the iflag=fullblock option, which will ensure the internal buffer is filled. Then count= will refer to the number of buffers processed, rather than the number of read()s. Also note if you specify ibs and obs seperately, then you will get writes of the size you requested at least. But be careful with using this behavior in conjunction with count=, as that will limit the number of read()s. cheers, Pádraig.
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