Simplicity is a form of art...

Switching OpenSSH to ed25519 keys

With Mike's news item on OpenSSH's deprecation of the DSA algorithm for the public key authentication, I started switching the few keys I still had using DSA to the suggested ED25519 algorithm. Of course, I wouldn't be a security-interested party if I did not do some additional investigation into the DSA versus Ed25519 discussion.

Updates on my Pelican adventure

It's been a few weeks that I switched my blog to Pelican, a static site generator build with Python. A number of adjustments have been made since, which I'll happily talk about.

My application base: Obnam

It is often said, yet too often forgotten: taking backups (and verifying that they work). Taking backups is not purely for companies and organizations. Individuals should also take backups to ensure that, in case of errors or calamities, the all important files are readily recoverable.

For backing up files and directories, I personally use obnam, after playing around with Bacula and attic. Bacula is more meant for large distributed environments (although I also tend to use obnam for my server infrastructure) and was too complex for my taste. The choice between obnam and attic is even more personally-oriented.

Switching to Pelican

Nothing beats a few hours of flying to get things moving on stuff. Being offline for a few hours with a good workstation helps to not be disturbed by external actions (air pockets notwithstanding).

Early this year, I expressed my intentions to move to Pelican from WordPress. I wasn't actually unhappy with WordPress, but the security concerns I had were a bit too much for blog as simple as mine. Running a PHP-enabled site with a database for something that I can easily handle through a static site, well, I had to try.

PostgreSQL with central authentication and authorization

I have been running a PostgreSQL cluster for a while as the primary backend for many services. The database system is very robust, well supported by the community and very powerful. In this post, I'm going to show how I use central authentication and authorization with PostgreSQL.

Audit buffering and rate limiting

Be it because of SELinux experiments, or through general audit experiments, sometimes you'll get in touch with a message similar to the following:

audit: audit_backlog=321 > audit_backlog_limit=320
audit: audit_lost=44395 audit_rate_limit=0 audit_backlog_limit=320
audit: backlog limit exceeded

The message shows …

D-Bus, quick recap

I've never fully investigated the what and how of D-Bus. I know it is some sort of IPC, but higher level than the POSIX IPC methods. After some reading, I think I start to understand how it works and how administrators can work with it. So a quick write-down is …

What is that net-pf-## thingie?

When checking audit logs, you might come across applications that request loading of a net-pf-## module, with ## being an integer. Having requests for net-pf-10 is a more known cause (enable IPv6) but what about net-pf-34?

The answer can be found in /usr/src/linux/include/linux/socket.h:

#define AF …

Managing Inter-Process Communication (IPC)

As a Linux administrator, you'll eventually need to concern you about Inter-Process Communication (IPC). The IPC primitives that most POSIX operating systems provide are semaphores, shared memory and message queues. On Linux, the first utility that helps you with those primitives is ipcs. Let's start with semaphores first.

Semaphores in …

Linux protip: environment for a process

Just a quick pro-tip: if you need to know the environment variables for a process, you can see them in that process' /proc/${PID}/environ file. The file however shows the environment variables on one line, with a null character as separator. With a simple sed you can show it …