At the start of September, I wrote about how concurrency is stillnot easy even in Go , using a sectionof real code with a deadlock as the example. In that entry , I proposed three fixes to remove thedeadlock. Since Hillel Wayne's Finding Goroutine Bugs with TLA+ has now formallydemonstrated that all three of my proposed fixes work, I can talkabout the practical differences between them.

For convenience, here's the original code from the firstentry :

func FindAll() []P

One of the things that makes Exim a powerful mailer constructionkit is that it has a robust set of string expansions ,which can be used to implement conditional logic among other things(examples include 1 , 2 , 3 , and 4 ).However, this power comes with an obscure, compact syntax that's more or less like a Lisp , butnot as nice, and in practice is surprisingly easy to get lost in.String expansions have an 'if' so you can implement conditionalthings and since they

Recently in the Fediverse, I read this toot :

Did you know that #Unix groups have passwords? Apparently if you setone, you then have to use newgrp to log in to that group.

I have never seen anyone use unix group passwords.

(Via @mhoye .)

There are some things to say about this, but the first thing youmight wonder is why the newgrp command exists at all. The bestanswer is that it's mostly a Unix historical relic (or, to put itanother

I was recently asked (in another context) if DKIM (Domain KeysIdentified Mail) was sufficiently common that one could start to require it on email,or at least use it as a strong part of spam scoring. Well, let'sget some statistics from our mail system. This has a different focusthan my October 2018 statistics ,where I was looking at total overall stats; here I'm going to tryto look only at email that seems good, based on being accepted by

For years, we've used Sophos PureMessage as the major part of ouroverall spam filtering . I don'tmention specific product names very often for various reasons, butit's now harmless because Sophos is dropping PureMessage ( also ).We were already planning to almost certainly replace PureMessagefor reasons other than this, but Sophos's decision to move to a cloudbased service model forces our hand.

(We actually have the replacement more or less planned out and willlikely start switching away from PureMessage very

One of my goals for my home desktop is to move entirely to solid state storage. Well, it's a goal forboth my home and work machine , and Ioriginally expected to get there first at home, but then work hadspare money and suddenly my work machine has been all solid statefor some time (which is great except for the bit where I'm not atwork to enjoy it).

Moving to all solid state at work was relatively straightforwardbecause all of my old storage on my

In yesterday's entry on our trouble free remote reboot of ourmachines , I mentioned that remote power controlfor all of our machines would be nice. When I said that, I wasinsufficiently specific, because there are actually two forms ofremote power control and we mostly have one of them, but it's notalways good enough. I will call these two sorts of remote powercontrol external and internal remote power control.

In external remote power control, your servers and machines areplugged in to a smart

Back in June I discovered that in theory we should have SPF recordsfor EHLO hostnames too . The conventional explanationfor this (apart from 'big email providers say so', the usual reasonto do anything in modern SMTP) comes from, for example, thiswriteup of small mailserver best current practices ,and goes like this (I'm paraphrasing):

People use SPF to validate the envelope sender domain (the SMTP MAIL FROM). However,when you send a bounce, it has a null sender and

Even under normal circumstances, we don't routinely reboot our Linuxservers. Reboots are disruptive to our users (especially to thepeople who are logged in to the servers that reboot), and localpolicies require us to schedule an after-hours downtime for largescale user visible things like this, which is disruptive to ourlives. We do reboot them periodically, either for significant enoughUbuntu kernel security issues or just because we want to get themback on up to date kernels. However, all of this is