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diff --git a/docs/textdocs/Tracing.txt b/docs/textdocs/Tracing.txt deleted file mode 100644 index d8b38378228..00000000000 --- a/docs/textdocs/Tracing.txt +++ /dev/null @@ -1,93 +0,0 @@ -Contributor: Andrew Tridgell <samba-bugs@samba.anu.edu.au> -Date: Old -Status: Questionable - -Subject: How to trace samba system calls for debugging purposes -============================================================================= - -This file describes how to do a system call trace on Samba to work out -what its doing wrong. This is not for the faint of heart, but if you -are reading this then you are probably desperate. - -Actually its not as bad as the the above makes it sound, just don't -expect the output to be very pretty :-) - -Ok, down to business. One of the big advantages of unix systems is -that they nearly all come with a system trace utility that allows you -to monitor all system calls that a program is making. This is -extremely using for debugging and also helps when trying to work out -why something is slower than you expect. You can use system tracing -without any special compilation options. - -The system trace utility is called different things on different -systems. On Linux systems its called strace. Under SunOS 4 its called -trace. Under SVR4 style systems (including solaris) its called -truss. Under many BSD systems its called ktrace. - -The first thing you should do is read the man page for your native -system call tracer. In the discussion below I'll assume its called -strace as strace is the only portable system tracer (its available for -free for many unix types) and its also got some of the nicest -features. - -Next, try using strace on some simple commands. For example, "strace -ls" or "strace echo hello". - -You'll notice that it produces a LOT of output. It is showing you the -arguments to every system call that the program makes and the -result. Very little happens in a program without a system call so you -get lots of output. You'll also find that it produces a lot of -"preamble" stuff showing the loading of shared libraries etc. Ignore -this (unless its going wrong!) - -For example, the only line that really matters in the "strace echo -hello" output is: - -write(1, "hello\n", 6) = 6 - -all the rest is just setting up to run the program. - -Ok, now you're famialiar with strace. To use it on Samba you need to -strace the running smbd daemon. The way I tend ot use it is to first -login from my Windows PC to the Samba server, then use smbstatus to -find which process ID that client is attached to, then as root I do -"strace -p PID" to attach to that process. I normally redirect the -stderr output from this command to a file for later perusal. For -example, if I'm using a csh style shell: - - strace -f -p 3872 >& strace.out - -or with a sh style shell: - - strace -f -p 3872 > strace.out 2>&1 - -Note the "-f" option. This is only available on some systems, and -allows you to trace not just the current process, but any children it -forks. This is great for finding printing problems caused by the -"print command" being wrong. - -Once you are attached you then can do whatever it is on the client -that is causing problems and you will capture all the system calls -that smbd makes. - -So how do you interpret the results? Generally I search thorugh the -output for strings that I know will appear when the problem -happens. For example, if I am having touble with permissions on a file -I would search for that files name in the strace output and look at -the surrounding lines. Another trick is to match up file descriptor -numbers and "follow" what happens to an open file until it is closed. - -Beyond this you will have to use your initiative. To give you an idea -of wehat you are looking for here is a piece of strace output that -shows that /dev/null is not world writeable, which causes printing to -fail with Samba: - -[pid 28268] open("/dev/null", O_RDWR) = -1 EACCES (Permission denied) -[pid 28268] open("/dev/null", O_WRONLY) = -1 EACCES (Permission denied) - -the process is trying to first open /dev/null read-write then -read-only. Both fail. This means /dev/null has incorrect permissions. - -Have fun! - -(please send updates/fixes to this file to samba-bugs@samba.anu.edu.au) |