Servers

I’m using Let’s Encrypt as Certificate Authority on this and many other sites. I like it, as it allows me to automate certificate creation and renewals, however I also have some monitoring making sure everything works as expected.

I recently got a few alerts as some certificates weren’t renewed as expected. I figured nothing had changed on the server setup and there was renewal happening for a few days, I started looking into it and found the issue why the renewal was failing, so here’s the story.

One of Linux five star things is the cronjobs. They allow you to automatically run stuf (scripts, applications, etc.) at quite specific times.

The crontab is the place controlling when the stuff is run and you can list the crontab using the commaand crontab -l for the current user.

If you want to edit the crontab, just use the command crontab -e and it launches the crontab in the default editor (set EDITOR env variable to change the editor used). The format is basically like this:

The site went offline a few hours today. Sorry.

It turns out Ubuntu once again changed a major component and the upgrade path didn’t work as it should to keep the lights on after the upgrade.

I’ve been updating the security settings on the server all around, and one of the things I wanted to do was adding TLSv1.3 support (and nothing before TLSv1.2). For that I needed, it seemed the best option to push forward the Ubuntu server version to the newer LTS version (18.04) and as part of this get a newer NGINX with TLSv1.3 support. That part worked sort of great.

My little server ran into an issue, and started reporting the error:

No space left on device

No worries, lest figure out which disk has full and clean up…

Using the df command with the -h (for human-readable output) it should be easy to find the issue:

root@server:~# df -h
Filesystem Size Used Avail Use% Mounted on
udev 483M 0 483M 0% /dev
tmpfs 100M 3.1M 97M 4% /run
/dev/vda 20G 9.3G 9.4G 50% /
tmpfs 500M 0 500M 0% /dev/shm
tmpfs 5.0M 0 5.0M 0% /run/lock
tmpfs 500M 0 500M 0% /sys/fs/cgroup
cgmfs 100K 0 100K 0% /run/cgmanager/fs
tmpfs 100M 0 100M 0% /run/user/1000

Strange. Notice who the /dev/vda is 50% fillled and all other disk devices seems to be finde too. Well after a little digging, thinking and googling, it turns out device space consists of two things - space (for data) on the device and iNodes (the stuff used to mange the space - where the data go - simplified).

I’ve switched nameservers for all my domains yesterday. During the past many years I’ve been free-riding on GratisDNS and enjoying their free DNS service (and luckily never needed support in their forums).

Yesterday I switched to Cloudflare and I’m using them for DNS for this (and other domains). I don’t have any particular requirements, and the switch was mostly easy and automated to the extent possible. Two domains went smooth, but the last my mahler.io domain went a stray a few hours during the switch.

Get your company implementing DMARC now…

During the past 5-6 years email industry efforts have been pushing the DMARC standard along. It provides the best widely supported and seemingly efficient way to - as a domain-owner - protect the domain from misuse and abuse in terms of spam and phishing attacks.

As sending email has often been a wild-west, and knowing who is a valid sender of email may prove a challenge for many companies - and as most IT developers does seem to care too much about the finer details of email (and production just as bad email headers as HTML markup :-) ), implementing DMARC protection on your domain may actually be a challenge.

Google has come up with a nice new image format called webp. Currently support for this format is fairly limited, so if you need to use webp images else where it might be nice to convert them to a more widely supported format. To do the conversion, Google has made a small tool available called dwebp. The tool however does only seem to support conversion of a single image, not a batch of images.

So I’ve installed a Raspberry Pi and it’s been running smoothly day in, day out. I’d like it to stay that way, but as the server is running it’s gathers lint in log files, databases grows and knowing how the load on CPU and memory is utilized through out time, I was looking for a tool which could help me to solve this problem.

As fun as it might be to build your own solution, I’ve learned to appreciate ready to use solutions, and it seems a nice little tool is available called RPi-Monitor. Assuming you run the Raspbian, the RPi-Monitor is available as a package ready to install through the standard package manager (once you’ve added the package repository).

Here’s a little trick, which is has proven itself just as useful as it is easy. To most companies handling domains is critical task, as losing your domain name may have catastrophic consequences. Handling domains isn’t particularly hard, but there are some tasks, that may be time-critical to handle in due time - luckily Google Calendar provides an easy way to help make sure these tasks are handled.

(In this little tip, I’m using Google Calendar as the reference, but Outlook.com, Office365 or any other online calendaring system can probably do the same.)

For some time the server running this site had been acting up. Page loads were slow, access through SSH seemed lagging and something was absolutely misbehaving.

I’ve been trying to figure out what exactly was going on, but nothing really made sense. there were plenty of disk space, memory was reasonable utilized (no swapping) and the CPU load seemed to be less than 0.1 at any time - there were no good reason the server was “turtling” along at such a perceived slow pace.