Archive for category best practice
Seven years ago we started an “IPv6 project”. The goal was to deploy IPv6 throughout our internal game studio network. After two months of analysis, I approached my boss and recommended we kill it. At least as an “IPv6 project”. It was reborn as a “clean up our network architecture, and oh by the way, add IPv6 (and a bunch of other things)”.
Wow, I’m behind. It was a busy year, and not a lot going on that I could really talk about publicly.
The recent meltdown and spectre bugs have brought back some memories from Orange Book days. I’ve also been spending a lot of time thinking about “IT transformation” and non-technical stuff. I’ve also been to the UK and Japan, twice, each, which may become the “new normal”.
Let’s see what happens in the next 12 months.
I think I’ve found one of the answers to a long-annoying Zabbix issue related to SNMP items “flapping” from “became supported” to “became not supported”.
TL;DR – using an SNMPv1 query against an SNMPv2 device will confuse Zabbix. You’ll see intermittent failures of different tests as the device flaps between OK and “unknown”. This can be hard to track down, as its’s not a hard repeatable failure. It’s not the only cause of this error, but fixing this will solve many of the issues.
While looking through our Zabbix server logs I found LOTS of these:
2031:20161027:111122.224 item "netapp-cluster.thuktun.com:netapp.disk.prefailed.count" became supported 2028:20161027:112119.172 item "netapp-cluster.thuktun.com:netapp.disk.prefailed.count" became not supported: SNMP error: (noSuchName) There is no such variable name in this MIB. 2030:20161027:120146.448 item "netapp-cluster.thuktun.com:netapp.disk.prefailed.count" became supported 2028:20161027:122120.026 item "netapp-cluster.thuktun.com:netapp.disk.prefailed.count" became not supported: SNMP error: (noSuchName) There is no such variable name in this MIB.
All of these referred to a NetApp in cluster mode, but I found a few similar messages related to some “NetBot” cameras around as well. Additionally, the actual test item varied; there were about 6 different tests that were all failing intermittently. The failing tests were:
A few Google searches returned some items related to this kind of issue, back to 2013
- https://www.zabbix.com/forum/showthread.php?t=38912 (LenR mentions: “Should the items be zabbix-trapper instead of zabbix-agent? I think I’ve seen this with incorrectly defined zabbix-sender updated items.”
- https://www.zabbix.com/forum/showthread.php?t=22114 (This shows that this has been seen as far back as 2011)
- http://serverfault.com/questions/761645/zabbix-issue-with-lld-lots-of-became-supported-became-not-supported (“should be using Zabbix trapper instead of …)
All of these are talking about Zabbix trapper vs Zabbix agent, that is using the wrong type of check for the test item, but no mention of SNMP.
Let’s look at the Zabbix configuration. Are we using the trapper or the agent for these test items?
Note that the NetApp template doesn’t use the Zabbix trapper or agent, it uses SNMP. But, some tests are SNMPv1 and some are SNMPv2. This is likely due to the fact that some versions of NetApp have had varying support for v1 and v2 over the years, and whoever created the template originally started with just v1. Over the years, as more test items were exposed, new tests were added, but using SNMPv2 and the old tests were left at SNMPv1?
Interesting. All of the failing tests are using SNMPv1. Not all v1 tests are failing, but all failing tests are using v1. There’s nothing here about Zabbix trapper or the Zabbix agent, but there is a (potential) mismatch. This shouldn’t be a problem, but let’s find out.
Over the next few hours, as each failure showed up in the Zabbix logs, I switched that particular test to SNMPv2. After being changed, that test never again “flapped”.
It seems that the keys to solving this were:
- LenR’s comment from 2013 about incorrectly defined items (although he was mentioning the zabbix-sender, not SNMP)
- Realizing it wasn’t a problem with the trapper vs agent, or an incorrect item definition in the agent, but that it was a mismatch in the server’s definition in the test item.
- That SNMPv1 and V2 are being treated differently in the Zabbix server, and that usually doing a v1 test against a v2 device will usually work, but not always.
- The “soft” failure of the v1 test against the v2 device “presents” as a MIB problem (“SNMP error: (noSuchName) There is no such variable name in this MIB.”), not a protocol failure.
I changed all of the failing NetApp tests to SNMPv2 last week. Since then all the tests that were changed from SNMPv1 to SNMPv2 have been fine. There have been none of these errors in the logs for 5 days.
Next: What about those NetBotz? Or maybe Zabbix meets IPv6 🙂
Hooray! AWS users can now serve their DNS info over IPv6. You could serve AAAA records before, but only over IPv4.
This finally gives AWS customers a way to deal with IPv6-only customers (as are appearing in Asia), who might have otherwise had to depend on ISP proxies or CGN (Carrier Grade NAT), host their DNS elsewhere, or be unable to reach services hosted in AWS.
I got a great followup from my domain registrar Register4less today. A few weeks ago, I had asked about when their DNS would fully support IPv6.
They’ve allowed AAAA records in their hosted DNS for years, but they only accepted queries over IPv4 until this week.
This is just another reason that I love R4l’s support. When I had asked them about IPv6 DNS before, they said it was coming “soon”, but couldn’t give a for-sure date, but would let me know.
When they turned up IPV6 DNS this week, they proactively sent me an email letting me know that the service was available, answered a few questions (within literally 5 minutes!).
Register4less.com is the official DNS provider of UserFriendly.org. If you work IT, you should know this long-running webcomic.
Let’s get started recovering the site. See Part 1 for the background. Note that I actually did this recovery in February 2015, and some software may have changed since then.
1. Dump the DB of the infected site in the test SQL dump format. This creates a human readable (and editable) file on my laptop.
There are all kinds of tutorials out there on dumping a SQL DB using phpMyAdmin. They are all better than I could write. This one, for example.
2. Examine and edit the DB dump file to remove any obvious damage. Is it worthwhile to continue?
For this I used Emacs. Yes, Emacs. You can use any test editor that you understand well, that has a “repeat this edit” or a general “search and replace” function. It must handle long lines, as each DB record is on a single loooong line. It helps if the editor can deal with escape characters. To make a long story short, the damage was almost immediately obvious. I was able to find the suspect lines and ^K (kill) them pretty quickly. For large values of “quickly”. There were about 1500 damaged or bogs records. Using search/replace and making a “fine pattern and kill line” worked wonders.
OK, after about 45 minutes of editing, I’ve got a clean database. All the records that I see are (probably) valid WordPress code/values or (probably) valid user records, or image pointers. It’s worthwhile to continue.
However, there’s still some cleanup, and this is a raw mySQL dump. I can’t import this into WordPress.com, yet. For that I need a WXR format dump, and this WordPress version was so old, that WXR isn’t even supported. I need a modern WordPress install somewhere that will accept the old MySQL dump and then allow a WXR export.
3. Install stand-alone WordPress somewhere (but how, and where?)
I’m going to use this new environment to examine the site in a sandboxed environment and get a chance at some forensics and to more completely assess the damage. This will also be the bridge between the raw mySQL dump and the WXR file that I import into WordPress.com later.
I expected that installing a new host and WordPress to take the most time of the entire process. In the olden days I would start with a physical host, do a full Linux install, add mySQL, Apache, etc and eventually WordPress. I don’t want to take this much time.
What’s the fastest, easiest way to get a full-blown WordPress setup? Turns out, the cloud is a pretty good place to start.
Three years ago I wondered when wordpress.com would begin to support IPv6. The irony of hosting a blog that talks a lot about IPv6 on an IPv4-only platform is not lost on me 😦
This is not an OS issue, a load balancer issue, a PHP language issue, or even a WordPress software issue. I’ve seen WP software running full dual-stack, no problems. Five years ago. I’ve done it myself, I just don’t want to run WP myself anymore.
For whatever reason, WordPress.com has not decided to commit to the future. yet.
Seriously. Just stop that.
Stop disabling IPv6 as part of your standard OS install and network configurations.
If you’re like a lot of IT shops, you’ve probably been building “golden images” of your operating systems to use as the template for OS installation. While these images are (hopefully) on a regular patch cycle after installation, the basic configurations and options can remain unchanged for years.
The upshot of this is that there are a lot of operating system images out there that were initially created around the time that the base OS was released, and which have had minimal changes since then, other than mandatory patches.
Windows 7 and Server 2008R2 were released in 2009. Centos 5 was released in 2007. Both are still in very wide use. Even if you’ve moved up to Windows Server 2012 or Centos 6 (both released in 2011), it is not uncommon for golden images of these to retain the network and other configurations such as IPv6 from prior versions.
In other words, it is quite likely that your brand new OS install is using assumptions and configurations from 2009 or even 2007, when it was still considered good practice to disable IPv6 at every opportunity. We’re beginning to see new OS features, such as DirectAccess, that require functioning IPv6, either native or tunneled.
I have yet to find any service that’s available in the MacOS X, Centos or Ubuntu systems that can’t make use of IPv6, or is negatively impacted in any way by dual-stacking the host. I have also not found any instance where taking a dual-stack-capable host onto an IPv4-only network has caused an issue, in at least 2 years.
So just quit disabling IPv6 by default, mmmkay?
They all have their uses, but seem to be just too shallow for tech, and life.
Face it, when you need an answer to a technical question or learn about something that isn’t in Wikipedia, chances are that Google will lead you to a blog post. Not a Facebook page (not indexed, and rarely technical). Not Twitter (how much can you explain in 140 characters?) And probably not Google+, either (although there is sometimes good discussion there).
Nope, you’re going to end up at someone’s blog post. Someone who faced the same problem, did their homework, pulled together from other sources, and solved the problem.
Go to Twitter for breaking news, Facebook for your friends, and Google+ for interesting discussions.
But the next time you solve a problem, how about you contribute to the world-wide-knowledgebase via a blog post somewhere?
Since my first trip to Europe 5 years ago, I’ve been trying to get a chip-and-pin credit/debit card. As far as I have been able to find out, other than a single credit union in DC, there is no way to get a chip-and-pin card in the US. American Express and others have chip-and-signature, but that’s not the same, even if they try to tell you that it is. For example, you can’t use chip-and-signature at unattended gas stations, vending machines or many other places in Europe.
It looks like, finally, the American card industry is willing to truly join the EMV card world, and issue chip-and-pin by 2015. It only took 10s of millions of credit cards numbers being stolen within a single month or so, to get them to move.
Almost all of our credit and debit cards were re-issued to us in January, by several credit unions and other financial institutions. That had to be expensive for all of them, and there is talk of the banks suing Target over their breach.
While this won’t end credit card fraud completely, it will definitely make it more difficult.
Just one more thing to think about as I work on my personal privacy…