dtrace

Welcome to 2012!

January 8, 2012 by Gleb Reys Leave a Comment

Hi all, happy New Year!

Just thought I’ll take a few minutes to welcome you to the new year and to thank you once again for staying with the Solaris Blog for so long!

My plans for this blog are quite humble in the view of Solaris not being a primary Unix-like OS at work anymore, but I’m still quite curious about a few things and would gladly share knowledge and answer your questions to my best ability.

So far, the following topics appear to be most useful:

Anything to do with SSH (stay tuned and take a minute to become RSS reader of my Unix Tutorial blog – I plan on releasing an SSH eBook later this year which many of you will find useful) – yes, it will cover passwordless SSH and will have some of the best X11 forwarding recipes
DTrace tips – still my favorite from Solaris 10 times, DTrace is truly amazing. I’m both surprised and glad that it made its way into many other operating systems. If anything, I’ll be sharing occasional tips on DTrace in Mac OSX. I will assume you’ve all seen Brendan Gregg’s excellent DTrace Tools kit!
ZFS – this proved to be so useful and revolutionary at the time that ZFS can now be found in a number of appliances and OS distros for NAS storage management (hello ZFS Build, Nexenta and Zena Box!)

I plan to expand sections of the blog covering these topics, but will gladly add anything you may find useful enough to flag in the comments section.

I’m really looking forward to 2012, and hope there will be more than one occasion when you will find my tips useful and readily applicable. Talk soon!

DTrace: mod_auth_pam and apache2

May 2, 2009 by Gleb Reys 3 Comments

One of our users has asked me to help with PAM authentication for Apache 2 on one of our remote servers.

Note: going with mod_auth_pam was decision made without me, and I was only asked to help get the chosen solution work. This being said, the recommended way to do external authentication for Apache 2 now is to use the mod_authz_external module and pwauth password authenticator.

It did seem like a rather trivial task – download mod_auth_pam, compile it for Apache 2, make sure everything works. The remote server uses NIS, I could freely log onto it.

And you know what? It didn’t work!

Debugging PHP with DTrace, part 2

May 2, 2009 by Gleb Reys Leave a Comment

Your next step in observing PHP with DTrace could easily be the following script. It times how much time (in nanoseconds) each Apache process has spent running a particular PHP function.

This script generates a table of Apache PIDs and PHP scripts started within, and later you’ll get a table of all the functions with PIDs which ran them and the time spent.

Passing command line parameters to DTrace scripts

May 2, 2009 by Gleb Reys 1 Comment

When you’re writing a DTrace script, often you’d like to pass some parameter in command line. Such an easy task might be really hard unless you read a docs.sun.com section about DTrace scripting, particularly a section about command line parameters macros.

As with sh or bash, you can access command line parameters via $0..$9 macroses. But there’s a catch. Values of these macroses should match a certain definition – a number, an identifier or a string. If there isn’t a match here, you’ll get an error.

Let’s start with a simple script. [Read more…] about Passing command line parameters to DTrace scripts

DTrace: Aggregations

May 2, 2009 by Gleb Reys 1 Comment

Quite often it is more important for you to see the whole picture, rather than to know each case when a particular probe fires. For instance, observing a process which consumes a lot of CPU time according to prstat, we ask ourselves: what is this process doing? And often we think about the overall number of system calls executed by this process, and not every particular one of these system calls.

DTrace aggregations are created specifically for answering such questions. Working with sets of numerical data, aggregation functions help us to easily determing average, min and max values of data sets, count numbers and sums of elements in these data sets, and even build frequency distributions.

[Read more…] about DTrace: Aggregations