I've written before about SSH connection sharing (and how I use it ), but Ishould mention that there is one little obscure gotcha with it. Theone gotcha is that all sessions inherit at least one thing from theinitial session, instead of setting it up from scratch.

Specifically, X forwarding is only set from the initial session .All ssh sessions over the shared connection channel will use the Xforwarding set up for the initial session and thus talk to whatever Xdisplay it was connected to, regardless

At the end of my previous entry on TTY line disciplines I wrote:

Given all of this, you might wonder why sophisticated readline styleediting took off as user level code (both in programs and as variouslibraries) instead of being integrated into the kernel. [...]

Well, let us start out with what we could call the pragmatic reason butshould more honestly call the political one: it is a lot easier to addsomething to your user-level program than to get it included in any Unix

Recently on Twitter there was a little conversation ( 1 , 2 , 3 , 4 )about smart editors for programming, by which people meanteditors that support things like auto-indentation and syntax highlighting. I have to confess that I have a very ambivalentattitude towards such fancy (or smart) editors and that I oftenwind up not using them.

In theory an editor with auto-indentation, syntax highlighting, and soon is a great thing. In practice, the implementations of all of theseare often not

Because I just had to research this (right down to reading kernel source),here is how the Linux kernel handles its command line arguments.

(The kernel command line is set in the bootloader in various ways. Grublets you edit it on the fly, assuming that you can interrupt grub intime before it autoboots your kernel.)

First, the kernel goes through all kernel options andhandles them. In theory all of the kernel options aredocumented in Documentation/kernel-parameters.txt inthe kernel source

A while back, Brendan Gregg left a comment on my entry about why we haven't taken to DTrace . In one part, he asked:

I was a little confused at first about the language and documentationissues [with DTrace]. Usually language discussions [...] are intendedto pick one over another, but in this case there is no other optionto choose from. So if these problems are raising the barrier toentry for some people, and they aren't entering, then what are

One of the irritating things about Apache's handling of redirects isthat it makes what I suspect is the most common case the more verboseand potentially complex to handle, especially if you want to put it ina .htaccess file instead of in the main Apache configuration. Since Ijust had to go through working this out for our use, I'm going to writeit down in case I need it later.

Suppose that you have an Apache server and you want to redirect thelocal URL /~user

WanderingThoughts has been getting comment spam attempts for what is nowa rather long time; I last wrote about the state of affairs two yearsago . Since then nothing much has changed (atleast at one level), but I've come to a general conclusion about how mycurrent comment spammers operate.

(I'm not sure I can generalize to all comment spammers, since I onlyhave one blog data point. But I would be rather surprised if my commentspammers were atypical.)

The big thing I

Django has native AJAX support for serializing model objects and query results to and from JSON (orXML) ;various people have then added various featureful packages on top of this. For myweb app all of this was overkill and toocomplex. What I needed for my limited client side form validation was a simple AJAX endpoint service,one that reported whether or not a potential login name was acceptableby returning a JSON dictionary with both a validity flag and a messageto display to the user about the situation.

(I

In the previous entry I went throughthe kernel messages printed when one of our Linux servers had a pageallocation failure. Now it's time to explain why our server had thatfailure despite what looks like plenty of memory. To refresh, thekernel was trying to allocate a 64 Kbyte ('order 4') chunk of contiguousmemory in the Normal zone . There was no such chunkin the server's small Normal zone, but there were several such chunksfree in the DMA32 zone (