Grains of Salt | BSD Now 344

Shell text processing, data rebalancing on ZFS mirrors, Add Security Headers with OpenBSD relayd, ZFS filesystem hierarchy in ZFS pools, speeding up ZSH, How Unix pipes work, grow ZFS pools over time, the real reason ifconfig on Linux is deprecated, clear your terminal in style, and more.

Headlines

Text processing in the shell

This article is part of a self-published book project by Balthazar Rouberol and Etienne Brodu, ex-roommates, friends and colleagues, aiming at empowering the up and coming generation of developers. We currently are hard at work on it!

One of the things that makes the shell an invaluable tool is the amount of available text processing commands, and the ability to easily pipe them into each other to build complex text processing workflows. These commands can make it trivial to perform text and data analysis, convert data between different formats, filter lines, etc.

When working with text data, the philosophy is to break any complex problem you have into a set of smaller ones, and to solve each of them with a specialized tool.

Rebalancing data on ZFS mirrors

One of the questions that comes up time and time again about ZFS is “how can I migrate my data to a pool on a few of my disks, then add the rest of the disks afterward?”

If you just want to get the data moved and don’t care about balance, you can just copy the data over, then add the new disks and be done with it. But, it won’t be distributed evenly over the vdevs in your pool.

Don’t fret, though, it’s actually pretty easy to rebalance mirrors. In the following example, we’ll assume you’ve got four disks in a RAID array on an old machine, and two disks available to copy the data to in the short term.

News Roundup

Using OpenBSD relayd to Add Security Headers

I am a huge fan of OpenBSD’s built-in httpd server as it is simple, secure, and quite performant. With the modern push of the large search providers pushing secure websites, it is now important to add security headers to your website or risk having the search results for your website downgraded. Fortunately, it is very easy to do this when you combine httpd with relayd. While relayd is principally designed for layer 3 redirections and layer 7 relays, it just so happens that it makes a handy tool for adding the recommended security headers. My website automatically redirects users from http to https and this gets achieved using a simple redirection in /etc/httpd.conf So if you have a configuration similar to mine, then you will still want to have httpd listen on the egress interface on port 80. The key thing to change here is to have httpd listen on 127.0.0.1 on port 443.

How we set up our ZFS filesystem hierarchy in our ZFS pools

Our long standing practice here, predating even the first generation of our ZFS fileservers, is that we have two main sorts of filesystems, home directories (homedir filesystems) and what we call 'work directory' (workdir) filesystems. Homedir filesystems are called /h/NNN (for some NNN) and workdir filesystems are called /w/NNN; the NNN is unique across all of the different sorts of filesystems. Users are encouraged to put as much stuff as possible in workdirs and can have as many of them as they want, which mattered a lot more in the days when we used Solaris DiskSuite and had fixed-sized filesystems.

Speeding up ZSH

https://web.arch