Sean, I will accept my portion of the proceeds in the form of a voucher which can be redeemed for technical support ;)

In all seriousness, you give far more than you get from me so congrats on the articles and keep em coming!

John

On Wed, 2007-02-21 at 14:12 -0600, Sean Walberg wrote:

Check out the one on troubleshooting VoIP with Wireshark, too ;)

I must also thank John Lange and Bill Reid for letting me bounce stuff off them for those articles, and to Les Bester for setting me up with an account to test the SIP connection tracking.

Sean

On 2/21/07, Bill Reid billreid@shaw.ca wrote: The March Linux Journal has a few articles on Asterisk including one by Sean Wallberg on VoIP and NAT.

    Congrats Sean on getting your article published.

    -- Bill
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-- Sean Walberg sean@ertw.com http://ertw.com/ _______________________________________________ Roundtable mailing list Roundtable@muug.mb.ca http://www.muug.mb.ca/mailman/listinfo/roundtable

At first glance it doesn't care much.

[sean@bob ddtest]$ echo "hello" > test [sean@bob ddtest]$ ls -l test -rw-rw-r-- 1 sean sean 6 Feb 21 21:43 test [sean@bob ddtest]$ dd if=test of=test.out bs=1k 0+1 records in 0+1 records out 6 bytes (6 B) copied, 0.000157303 seconds, 38.1 kB/s [sean@bob ddtest]$ ls -l test.out -rw-rw-r-- 1 sean sean 6 Feb 21 21:43 test.out

Flip through the source code to dd.c:

/* The number of bytes in which atomic reads are done. */ static size_t input_blocksize = 0;

/* The number of bytes in which atomic writes are done. */ static size_t output_blocksize = 0;

You'd have to browser a bit deeper to get the One True Answer, there looks like there are several different types of copying that can happen, each has different behaviours.

notrunc is a bit easier, it's only referenced in two places, both in the same function. It seems to be a direct setting/clearing of O_TRUNC to open(2):

O_TRUNC If the file already exists and is a regular file and the open mode allows writing (i.e., is O_RDWR or O_WRONLY) it will be truncated to length 0. If the file is a FIFO or terminal device file, the O_TRUNC flag is ignored. Otherwise the effect of O_TRUNC is unspecified.

Sean

On 2/21/07, Dan Martin ummar143@cc.umanitoba.ca wrote:

Can someone tell me how the dd command handles block sizes? The man page and any Linux books I have don't explain it very well.

If I specify dd if=\dev\mydevice ... bs=1M What happens if mydevice has a fraction of a block left over?

What is "notrunc" for the output file? Truncation from what to what?

-- -Dan

Dr. Dan Martin, MD, CCFP, BSc, BCSc (Hon)

GP Hospital Practitioner Computer Science grad student ummar143@cc.umanitoba.ca (204) 831-1746 answering machine always on

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