Category: Linux

Posted on in Linux, Server

Proxy-set-header: Forwarding HTTP headers from Nginx to a WordPress container

I detailed in a recent post how I got a working WordPress container setup, complete with database and PHP engine. I saved the bit about how to redirect traffic to the container (and apply encryption to the outbound connections) because I knew it was going to be just as much work as getting the setup running. Also I needed to first get up to speed on HTTP headers in general and how to inspect them specifically.

This post is not a how-to any more than it’s a how-not-to. I wanted to detail as much the attempts that did not work as the final one that did because the former were just as illuminating as the latter.

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Posted on in Linux, Server

My life as an IP hobo and the promise of Dynamic DNS

When your servers don’t respond / who you gonna call? Well, maybe not call but look. And I’m talking about my server residing on my HTPC not yours. And it’s rhetorical question anyway because I know where to look once I get home. At one of the many what-is-my-ip address sites because the problem inevitably boils down to my ISP having changed my IP address.

This may elicit “duh”s from people whose IP addresses change every lunch break but mine used to be stable for months if not years on end. So I never bothered with my ISP’s 2€/month offer of a permanent IP address. Recently though, they changed their practices and now I rarely get in to a new pair of underpants before the address has changed. Read into that what you will. Oh, also the offer is 4€/month now. Coincidence? /conspiracy

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Posted on in Linux, Server

Moving site: Using MySQL to search-and-replace WordPress domain name

It seems that the recommended way to change the references to the domain name in MySQL on a WordPress install is to take the whole thing offline and do it by using text tools on a database dump. Either that or change the settings in WordPress while the site is still live on the old domain.

It was too late for the latter and I could not be bothered to do the former – partly because I had just gone through the whole mysql dump routine, partly because the site I wanted to move was only one among a number of sites contained in the dump. While the web server was all set up to use the new domain name, WordPress persisted in redirecting me to the old.

So I looked at the recent database dump, figured out what tables and fields to target so that I could replace the domain name on a live install.

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tea shark
Posted on in Linux

Inspecting HTTP headers with tshark

Redirecting traffic from an nginx reverse proxy to a docker container I needed to add some forwarding information to the http headers. And so I figured I had better start wrapping my head around what http headers actually were, how they looked and how my nginx settings were impacting them. Enter tshark, the command line version of Wireshark.

Wire-/tshark are general purpose packet analyzers so the challenge here is to avoid casting a too wide net: I don’t want all the network traffic on my host, just the http headers and just those coming in and out of one particular virtual box.

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Posted on in Linux, Server

WordPress on Docker: The 1-2-3 approach

There’s an official WordPress docker image on the hub. Which means I have no good excuse to go make my own. Here’s my bad excuse: The official approach contains Apache and WordPress files all mashed up in one image. This feels icky to me partly because I don’t know Apache, having decided early on to hitch my wagon to Nginx, partly because it feels un-containerly to have everything in one big pot.

I cannot argue the merits and demerits of the official image with regards to performance, scalability, or security. What I saw was an opportunity to solve the problem in a way that felt more correct to me – 1 network, 2 volumes, 3 containers,  – that would also work as a learning experience. Here’s how I did it.

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Posted on in Linux, Server

Let’s do Dovecot slowly and properly: Part 2 – Proper authentication

In part 1 we set up the very most basic dovecot install we could get away with. In this part we will try to redeem it a bit by improving the security of the the authentication mechanism and the storage of passwords on the server. In other words we will make it much harder to snoop on our communications with the imap server and decrease the overall likelihood of somebody learning our password, including anybody with access – legitimate or otherwise – to our server.

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Posted on in Linux, Server

Let’s do Dovecot slowly and properly – Part 1: PLAIN as day

This post follows up on the fifth installment in my Let’s do Postfix series. We’re not really done setting up Postfix but a) it’s about time we had a better way of accessing incoming mail than ssh’ing into our server and using cat to read and b) we are at a juncture where the two will soon start depending on (SASL) and interacting with (LMTP) each other

This tutorial presumes knowledge of Postfix and the setup we’re aiming for is one that complements the Postfix one that we’ve set up in previous installments. As with the Postfix series I want to arrive at a working setup from the very first post but knowing full well that it’s not an ideal or final setup. The advantage (over importing somebody else’s full featured setup) is that we’ll actually understand what we have on our hands (and it’s shortcomings). This makes it a lot easier to build and improve upon it and fix it should the need arises.

A note on safety: The setup we’ll end up with today is not going to be confidential in any way, shape, or form. It will expose both the contents of the account’s emails and whatever password you choose to the entire internet. Therefore you should obviously use either a test account or a brand new one that has nothing important on it yet. As for passwords you should pick one for testing that you have not used nor intend to use for any non-testing purposes. That said, un-confidential is not the same as unsafe. Any public facing service is a potential attack vector but this setup is – to the best of my knowledge – no more of one than a more properly confidential setup.

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