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Cake day: July 1st, 2023

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  • In my system, the raid arrays seem to do periodic data scrubbing automatically. Maybe it’s something that’s part of Debian, or maybe it’s just a default kernel setting. I don’t think it helps much with data integrity – I think it helps more just by ensuring the continued functionality of the drives.

    When it’s running, you can type cat /proc/mdstat to see the progress.

    That command will also show you if there is a failing drive, so that you can replace it.



  • Epigenetics is black magic to me. The starvation thing is true, but it mostly happens in the liver and pancreas and stuff. The testicles and ovaries don’t express the genes relating to starvation, even when starved. So how does the reproductive DNA pass on epigenetic data to the child and grandchild?


  • Sure. First you set up a RAID5/6 array in mdadm. This is a purely software thing, which is built into the Linux kernel. It doesn’t require any hardware RAID system. If you have 3-4 drives, RAID5 is probably best, and if you have 5+ drives RAID6 is probably best.

    If your 3 blank drives are sdb1, sdc1, and sdd1, run this:

    mdadm --create --verbose /dev/md0 --level=5 -n 3 /dev/sdb1 /dev/sdc1 /dev/sdd1

    This will create a block device called /dev/md0 that you can use as if it were a single large hard drive.

    mkfs.btrfs /dev/md0

    That will make the filesystem on the block device.

    mkdir /mnt/bigraid
    mount /dev/md0 /mnt/bigraid
    

    This creates a mount point and mounts the filesystem.

    To get it to mount every time you boot, add an entry for this filesystem in /etc/fstab



  • Any regular hex nut works just fine as a jam nut. Basically, a jam nut is when you jam two nuts together. (It is gay, because the nuts do touch.)

    And note that those nylon inserts kinda only work once. The bolt carves a thread into the insert when you insert it, so it will be weaker the second time you insert it.

    Honorable mention: cage nuts. A square nut, permanently attached to a fastener that can snap into a special square hole in a 19 inch server rack. When you tighten the bolt against the nut, it tightens against the fastener, so that the nut, bolt, and fastener are secure against the square hole.




  • Unfortunately this won’t happen until October 31st 2600. Starting on March 1st in the year 2600, the Julian calendar (popular in centuries past, and still used in a few places) will differ by 18 days from the Gregorian calendar (the current worldwide standard calendar).

    It happens that October 31st in the year 2600 lands on a Friday, and so the Julian October 13th, which lands on that same day, is also a Friday.

    There may be a sooner Friday the 13th that lands on Halloween, if you know of other obscure calendars like the Hebrew, Islamic, or Chinese calendars. I don’t know enough about those to check.


  • The easiest way to disable unnecessary services is to uninstall them with aptitude, or whichever package manager you like. Try terminating services one by one, and see if anything bad happens. If nothing bad happens, you can probably uninstall it. On the other hand, if the system does get wonky a reboot should fix it. Or, you can research the services by name and decide whether to uninstall them. (avahi-daemon for example is a good idea to uninstall.)

    To make the GUI not run, uninstall your display manager (gdm, xdm, nodm, or whatever) and uninstall your xorg server or wayland server. There may be GUI programs remaining after that, but they will only be consuming disk space, not RAM or CPU.

    If the battery is old and holds little charge, you may save a few watts by removing it and throwing it away, instead of letting the system keep it topped off.

    Get a power meter, such as a Kill-a-watt device. Then, experiment with different settings. If it’s consuming less than 30 watts, you’re probably fine. If you live in the US, one watt-year is about one US dollar (or a little more), so for every watt it consumes, that’s about how much you will pay per year for its electricity.






  • I have three ideas: First, you could switch the desktop environment to one of the ones that has a GUI settings tool to set passwordless automatic sign in. I think Gnome 3 on Ubuntu, and Mate Desktop on Linux Mint have that feature. There are probably others.

    Second, you could switch your display manager to “nodm”. The display manager is the thing that runs the X server or Wayland, and it starts the greeter (the greeter is the program that shows the login screen). nodm is a special display manager that doesn’t use a greeter or ask for a password. It immediately starts the session using the username and desktop environment specified in its configuration file.

    I use nodm for my HTPC and it works very well. The only downside is that you have to edit its configuration file, /etc/default/nodm , using a text editor. I’m not aware of any GUI configuration tool for it. However, it’s pretty easy to configure.

    Third, you could abandon all display managers, and start the session manually, either from a shell script, or over SSH. This is a little more complex. You will probably want to get comfortable with SSH before trying this (SSH is the command-line analog of remote desktop).



  • I cannot recommend any USB-connected drive for long-term use. (Only for portable devices that get plugged in for a little while at a time.) In the long term, any USB drive will randomly reset during periods of heavy use – including heavy writes, meaning some data will get lost.

    USB enclosures tend to just crap out completely after a year or two, if used continuously on a server. I know because I twice used 1TB external drives with OpenWRT (home router) devices. The data will be safe on the drive, but you’ll have to replace the enclosure.

    1. My first recommendation would be to look very carefully at the chassis and see if there’s any way at all to fit another SSD inside it. 2.5" SSD’s are usually thinner than 2.5" hard drives, so it may be possible, and most motherboards have more SATA ports than they need.

    Is there possibly an NVMe slot on the motherboard? Or an open PCIe slot where you could put an NVMe adapter?

    1. My second recommendation would be using a 2.5" hard drive. Newegg has a 5TB one for $135, but unfortunately that’s as large as they seem to go. It will be a bit slower than an SSD, but still probably around 150MB/s for sequential access.

    2. My third recommendation, if money is really tight, would be an additional server, with a large 3.5" hard drive. This will be a lot cheaper than an 8TB SSD, but adds complexity, electricity use, space use, and possibly fan noise.



  • This is false. X is not less secure than Wayland. It does have a different security model, which can become insecure if you misuse it. I don’t think people really care about situations where multiple user accounts access the same display.

    In my opinion, the benefits of xdotool far outweigh any benefits gained by Wayland’s security model. It’s impossible to make xdotool in Wayland, because of its security model.