👣 Intro Tracing tools are pretty popular in the Unix/Linux ecosystem; for example in the userspace we have ltrace to trace library calls of the programs and strace to dive in deeper and inspect syscall usage. One of the many features that Linux kernel offers since 2008 (then evolved) is ftrace that allows many different kind of tracing at runtime. While not as flexible as eBPF technology, it can be helpful in some occasion and doesn’t require a full fledged programming language. ...

💾 Intro I just found a very cheap SD card on an online store and since I know that there are some fake around, I wanted to quickly test if its size and speed respect the specs. Edit: after first publish, a kind reader noticed me that The F3 tools are a perfect fit for the same task and that’s right; if you want to follow a manual path and learn something in the journey, continue reading… ...

🔐 Intro As an experienced sysadmin, you might be familiar with the traditional “all-or-nothing” approach: if a shell or process is running with UID==0, it can do almost everything on a system; while a plain user process is restricted by some means: tipically it can’t open RAW sockets, can’t bind “privileged” ports under 1024, can’t change a file ownership and so on. Linux capabilities is a feature, gradually introduced starting from kernel 2.2, that permits a more fine-grained control over privileged operations, breaking the traditional binary root/non-root distinction. Just as by using sudo we can run specific commands as another user (even root), without permanently becoming that user, by using capabilities, we can grant a program only certain privileges without having to run it as root. ...

🌡️ Intro For those running a datacenter, or just a simple homelab server, the arrival of summer heat means an increase in air conditioning use. On this post I asked myself how a Linux engineer can measure how much energy is the system consuming so we can start to reason about workload optimization for better power consumption patterns. 🔋 Idle power drain As a starting point, let’s measure how much power my PC is consuming when idle, doing absolutely nothing; or better: nothing useful for computation or service but just running usual, default operating system tasks. ...