As part of our Prometheus and Grafana setup we monitor our IMAP servers (we have more than one for reasons),and as part of that monitoring we verify not just that we can login but that we can do IMAP SELECT operations on various mailboxesthat are on various different fileservers (using a custom Python program ). When I added the mailbox SELECT sand their success metrics, I also decided to collect and report thetime it took, since we're not certain how well the IMAP serverperforms .

The idea of /dev/fd , which gives filesystem names to filedescriptors, is the core of the modern implementation of processsubstitution . There are several waysto implement this idea in the Unix kernel, starting from an old,simple, and brute force method to the modern methods that generallyuse some form of virtual filesystem for reasonsthat we'll get to.

The simple but brute force way to implement /dev/fd is with a realdirectory containing a bunch of miscellaneous character devices , somewhatsimilar to

Famously, everything is a file in Unix, at least in the originalResearch Unix, such as V7 Unix ( BSD Unix deviated from thisfor network stuff ). Files were files, directories were files , disks were files , serial lines were files, and so on. This was apretty revolutionary idea at the time. However, this was not implementedinside the kernel in any general way; instead, things knew that therewere various types of file objects and inodes, and handled themspecifically. As part

One perpetual appeal of about advanced filesystems like btrfs andZFS is the idea of making a snapshot of your root filesystem, tryingan upgrade, and then reverting to the snapshot if you feel thatthings have gone wrong. In my entry yesterday on why I use ext4for my root filesystems , I mentioned thatI didn't expect doing this to work as well as you'd like, and Aristotle Pagaltzis expressed interestin an elaboration of this. Well, never let it be said that I don't

A while ago, I read Julia Evans' Teaching by filling in knowledgegaps and hit the section using Evans' shell brackets cheat sheet as anexample. One of the uses of brackets in Bash and other shells is "process substitution" (also Wikipedia ),where you can use a redirection with a process instead of a fileas an argument to commands:

diff <(rpm -qa) <(ssh server2 "rpm -qa")

Process substitution is a great little feature and it feels veryUnixy

In a comment on my entry on checking what ext4 features yourfilesystem has , I was asked why I still useext4 for my root filesystem, when CentOS changed to xfs by defaultand Fedora changed to btrfs (Fedora may have defaulted to xfs forthe root filesystem for a while, I'm not sure). There are threeanswers to this, especially for btrfs.

The technical answer is that for my root filesystem I don't need any ofthe extra features that XFS or especially btrfs bring

I have new disks for my home desktop that are going to be used forthe root filesystem (and a ZFS pool), once I decide on partitionsizes . Since I have my existing rootpartition in a software RAID, there are two ways to move over tousing the new disks. First, I can add the new disks as additionalmirrors to the software RAID and let software RAID resync do atransparent copy and eventual migration, or I can make a new softwareRAID mirror, mkfs a new ext4

While pipx is a good way tomanage virtual environments for third party Python programs installedthrough PyPy, it necessarily still has some of the general issueswith upgrading programs with pip . Withpipx, though, the theoretically obvious solution to this is thatif ' pipx upgrade ' isn't making you happy any more, you can use' pipx reinstall ' to redo everything from scratch. However, one ofmy questions about pipx reinstall has always been if it would dealwith a virtual environment, such as one for the

Like many people who've been on the Internet for a long time, Iview email as a critical thing in the overall Internet ecology. Butfor a long time I probably would have just waved my hands if youasked me about why, and talked about its wide usage and practicalapplications and so on. I was recently reading j. b. crawford's DIY mail ( via ), in which crawford observesthat email is one of the first real Internet federated systems and alsoperhaps one of the last