I've been reading my way through Lisp as the Maxwell's equationsof software and ran into this 'problems for the author' note:

As a general point about programming language design it seems likeit would often be helpful to be able to define procedures in termsof other procedures which have not yet been defined. Which languagesmake this possible, and which do not? What advantages does it bringfor a programming language to be able to do this? Are there anydisadvantages?

(I'm going

Earlier today I wanted to lightly damage a disk in a test ZFS pool inorder to make sure that some of our status monitoring code was workingright when ZFS was recovering from checksum failures. The reason Iwanted to do light damage is that under normal circumstances, if youdo too much damage to a disk, ZFS declares the disk bad and ejects itfrom your pool entirely; I didn't want this to happen.

So I did something like this:

for i in $(seq 128 2

I'd like the CPU in my next machine to have ECC RAM, for all sortsof good reasons. I'm also more or less set on using Intel CPUs,because as far as I know they're still on top in terms of performanceand power efficiency. As I've written about before ,this leaves me with the problem that only some Intel CPUs andchipsets actually support ECC.

(It appears that Intel will actually give you a straightforwardlist of CPUs here , whichis progress from

In theory, my concerns about how other people's systems will reactto us DKIM-signing only some of our email have a simpleanswer; if we don't add DMARC information that says to react tounsigned email in some way, they should do nothing. This is thespec compliant behavior and you'd have to be really obnoxious todecide to do otherwise. But that assumes that spam scoring systemsare in fact deliberately designed, and my current belief is thatthe custom systems major email providers use

Almost five years ago I wrote about my then-new view of DKIM and how we might someday use it ourselves when we'dupdated our mailers enough. Well, the mailers have been updatedfor a while and not only aren't we using DKIM, I'm not inclinedto do so any time soon. Prompted by someone here asking for myopinions on DKIM today, here's my current views.

As far as inbound email goes, I've experimented with a Thunderbirdextension to verify DKIM

Let's start with my tweet :

The #CentOS 6 iptables package update unconditionally (re-)enablesthe service and thus turns on firewalls. BRB, setting things onfire now.

Really, it does. It's right there in the RPM postinstall script:

; rpm -q --scripts iptables[...]postinstall scriptlet (using /bin/sh):/sbin/ldconfig/sbin/chkconfig --add iptables[...]

Of course iptables by itself does nothing

Yesterday I wrote about what free was really telling you , using the output (and manpage) from the versionof free on Fedora 22. As Alan noted in a comment on my entry,there are actually two versions of free , with somewhat differentoutput. The older version reports:

; free -m             total   used   free  shared  buffers  cachedMem:         16018  15760    258       3       72   12924-/+ buffers/cache:   2763

The free command is a pretty venerable Linux sysadmin tool; oftenit's one of the first things I reach for when I suspect that asystem might be having RAM problems. Its normal output certainlylooks straightforward enough, but as I discovered recently it's always good to actually look upthe details of this stuff.

So let's start with the normal output:

; free -m      total   used   free  shared  buff/cache  availableMem:  32158  13111    683

Let me say up front that ' systemctl status ' is on the whole areally great command. The basic information it reports about aservice is very useful, and it's extra-useful that you can give ita random PID and it will tell you what it belongs to (and what allof the other processes are). There is just one little drawback toit, namely that it also helpfully defaults to showing you recentlog messages for the service.

In theory this is a great idea, because