Yes I know I still haven't done part two of that mail server post. I'll get it done soon, I promise.
While chatting on IRC, someone mentioned that they were having a problem with a process going mental and creating a bunch of file descriptors in linux, eventually hitting the "max FD limit" linux has. They couldn't figure out which process it was and they couldn't find a program that would list a count of how many FDs a process has open. A few minutes later I'd thrown together this bash one-liner for him. I'm posting it here just in case someone else might find it useful.
echo "$(for pid in $(ls -a /proc|egrep '^([0-9])*$'|sort -n 2>/dev/null); do if [ -e /proc/$pid/fd ]; then FHC=$(ls -l /proc/$pid/fd|wc -l); if [ $FHC -gt 0 ]; then PNAME="$(cat /proc/$pid/comm)"; echo "$FHC files opened by $pid ($PNAME)"; fi; fi; done)"|sort -r -n|head -n4
To explain: It loops through every file/folder in /proc that is a process ID, then checks that there's a file descriptor folder. Then it gets a count of all the FDs that process currently holds, gets the process name and outputs how many file descriptors that process has open, as well as the process name. This is then reverse-sorted and cut down to only the four processes with the most FDs open.
Okay yes I know I said the second part of my mail server post was incoming, it still is, but for now I'd like to break out and complain about something again.
Virgin Media recently announced a new 'Premiere' tariff for Virgin Mobile. This tariff gives you unlimited calls to landlines, 2500 minutes to mobiles, unlimited texts and unlimited data, for as low as Â£21 for existing Virgin Media customers.
As soon as I read "all-you-can-eat data", I was skeptical. Very few mobile operators offer truly unlimited data (and I'm with Three UK, who are one of maybe two operators here that offer proper unlimited data - their policies state that customers have an effective data cap of 1TB per month). So I did what anyone else does, and I looked up their policies (which you can find here), which state that:
Unlimited Mobile internet for daily use by Pay Monthly customers: We'll monitor how much mobile internet you use each month so that we can protect the network we use for all of our customers. If we consider your use to be excessive, we won't charge you any more, but we may restrict your access to the mobile web depending on how often and how excessive we think your usage is. As a rule of thumb, we are likely to consider any usage over 1GB per month to be excessive. Unlimited use is within the UK and is for your personal, non-commercial use only. It doesn't include making internet phone or video calls, peer to peer file sharing, using your phone as a modem, or while you are abroad.
Virgin Mobile are basically stating that they'll either restrict or throttle you if you use more than 1GB of data a month. That's hardly unlimited.
Then you've got the unlimited texts and landline minutes. But Maff, you may cry. How can Virgin screw up unlimited texts and landline calls? Quite easy. From the same document on virgin's website:
Unlimited texts: Unlimited texts are subject to a fair use allowance of 3000 texts per month. If your usage exceeds this amount then we reserve the right to charge you for the excessive element of your usage at the text rate for other mobile networks for your tariff outlined in our Tariff Table. Unlimited use is within the UK and is for your personal, non-commercial use only. It doesnt include texts to shortcode services, group text, or picture messages and any of these uses will be charged at the text rate for other mobile networks for your tariff outlined in our Tariff Table.
Unlimited landline minutes: Unlimited landline minutes are subject to a fair use allowance of 9000 minutes per quarter (3 months). If your usage exceeds this amount then we reserve the right to charge you for the excessive element of your usage at the rate for calls to landlines for your tariff outlined in our Tariff Table. Unlimited use is only for UK originating calls from the eligible Virgin Media phone to UK landlines (01,02 and 03 numbers). All other call types will be charged at the rates indicated in the Tariff Table and are not included in the allowance of minutes. Unlimited minutes are for your personal, non-commercial use only.
Right there. "Unlimited texts" actually means "3000 texts per month and we'll probably charge you standard rates if you go over that". "Unlimited landline minutes" actually means "9000 minutes per quarter year, and we'll probably charge you standard rates if you go over that".
Now it's fair to assume that most people won't use more than 3000 minutes or texts per month, but please, don't call that unlimited. It's misleading. As for Virgin's so-called unlimited data, I really don't understand how it can be called "unlimited data" when Virgin considers usage exceeding 1GB per month "excessive".
I really have nothing against Virgin, they were one of the first operators I was with (The other was BT CELLNET, now o2), and I'm sure their 3G network is great (I last used Virgin's network several years before 3G was even a thing in the UK so I have no idea, but the 2G network they had was good and coverage was always great), but it just rubs me up the wrong way when an ISP or mobile network provider claims that a service is "unlimited" - I did the same thing with BT when I discovered their top-tier "Unlimited 8mbps" broadband plan was actually subject to a fair use cap of 100GB. We didn't find this out until BT emailed us saying we'd hit 80GB that month and that we'd be billed for any usage past 100GB.
I'm happy to change this if I just found the wrong policies page on Virgin's website. If I pointed out the wrong policies and Virgin's "Premiere" tariff is subject to different policies, please point it out and I'll happily reflect that in this post.
So a few months ago, I moved my primary mail hosting to my own VPS. Over the months since then, I've been tweaking and adding to my mail system, and I figure it'd help both myself and others if I documented what I've done, so I'll start with a list of all the software I use.
In the near future, I'll write a second post detailing how I linked all this together, including config excerpts, but in this post I'm just discussing the software I used, as well as why I use each package. I'll also leave you with a list of extremely good tips.
One final thing to note, the guide and so on will discuss my current mail setup. This means it assumes you'll be using sockets for things like Postgrey. Please read everything carefully before making configuration changes to your own mail setup, as what works for me may not work for you.
That's all for now, but I'll be adding to this list, and writing a second post documenting how I actually set my mail system up, very soon. EDIT: Disregard that. Second part of this post will arrive eventually but I am tremendously lazy.
Since I figure it's bad form to have a blog and /only/ use it for ranting, here's a somewhat useful post. I've been with [a] [number] [of] [different] [hosts] over the past year or two, and I figure it'd be useful for others to know why I like or don't like them.
SimplexWebs has been in the hosting business for quite a while now, and do enterprise webhosting, online radio hosting and domains, as well as VPS (Xen, powered by OnApp) hosting. I was lucky enough to grab one of their limited birthday sale servers, which gave you 256MB RAM, decent CPU speed, 20GB disk and 100GB monthly bandwidth, for Â£25 a year.
This server's basically been my primary server/main workhorse - despite initially purchasing it to run a VPN server, and has held up ridiculously well. Uptime has been fantastic - my server's only been down a few times over the last half a year or so, including migrations between their old SolusVM platform to their new OnApp platform, and including the recent downtime when they moved datacentres.
Server and network speed are really good. I think this is one of the fastest servers I've ever used, and that includes the brief time I was with Linode. Support is fantastic, their team is always quick to respond and very helpful, and you definitely get the feeling that they actually care about their customers. Overall, they're one of the best hosts I've ever been with, and I don't feel I'll ever need to move to another host.
Here's some benchmarks:
~ wget cachefly.cachefly.net/100mb.test -O /dev/null --2012-04-28 02:34:32-- http://cachefly.cachefly.net/100mb.test Resolving cachefly.cachefly.net... 184.108.40.206 Connecting to cachefly.cachefly.net|220.127.116.11|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 104857600 (100M) [application/octet-stream] Saving to: `/dev/null' 100%[======>] 104,857,600 11.8M/s in 8.7s 2012-04-28 02:34:41 (11.5 MB/s) - `/dev/null' saved [104857600/104857600]
~ dd if=/dev/zero of=/tmp/disktest bs=64k count=16k 16384+0 records in 16384+0 records out 1073741824 bytes (1.1 GB) copied, 4.52632 s, 237 MB/s
Bhost are a UK-centric VPS provider, primarily dealing with OpenVZ servers although they've recently launched Xen PV plans. I should mention their servers are some of the cheapest you can get, the cheapest OpenVZ server being Â£4.70 (before VAT) and including 512MB RAM and 512MB burst RAM.
Their support is pretty great, considering they're a budget host, and the servers themselves are quite speedy. I do have some issues with the OS templates they have available - their Arch images are broken due to the host kernel being too old, although I'd say that's an Arch issue, and their Gentoo image is too old to actually use. Debian works fine though, so that's what I'm using. Overall, network and server speed is really good. Uptime is fantastic, in the entire time I've been with them (a number of months now), my server's almost never been down. Definitely one of the most reliable hosts I've been with.
Here's some benchmarks, since I still have a server with them: Network speed:
# wget cachefly.cachefly.net/100mb.test -O /dev/null --2012-04-28 02:30:40-- http://cachefly.cachefly.net/100mb.test Resolving cachefly.cachefly.net... 18.104.22.168 Connecting to cachefly.cachefly.net|22.214.171.124|:80... connected. HTTP request sent, awaiting response... 200 OK Length: 104857600 (100M) [application/octet-stream] Saving to: `/dev/null' 100%[======>] 104,857,600 10.2M/s in 9.8s 2012-04-28 02:30:49 (10.2 MB/s) - `/dev/null' saved [104857600/104857600]