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Cake day: July 24th, 2023

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  • You can also do the following to prevent unwanted writes when something is not mounted at /mnt/thatdrive:

    # make sure it is not mounted, fails if not mounted which is fine
    umount /mnt/thatdrive
    
    # make sure the mountpoint exists
    mkdir -p /mnt/thatdrive
    
    # make the directory immutable, which disallows writing to it (i.e. creating files inside it)
    chattr +i /mnt/thatdrive
    
    # test write to unmounted dir (should fail)
    touch /mnt/thatdrive/myfile
    
    # remount the drive (assumes it’s already listed in fstab)
    mount /mnt/thatdrive
    
    # test write to mounted dir (should succeed)
    touch /mnt/thatdrive/myfile
    
    # cleanup
    rm /mnt/thatdrive/myfile
    

    From man 1 chattr:

    A file with the ‘i’ attribute cannot be modified: it cannot be deleted or renamed, no link can be created to this file, most of the file’s metadata can not be modified, and the file can not be opened in write mode.
    Only the superuser or a process possessing the CAP_LINUX_IMMUTABLE capability can set or clear this attribute.

    I do this to prevent exactly the situation you’ve encountered. Hope this helps!






  • It’s probably best to limit yourself to a used laptop.

    Reading and writing code is nothing more than reading and writing text, and for that you don’t need a fancy gpu or screen.

    What I would recommend you look for in a laptop is

    • an SSD instead of an HDD
    • more cpu cores (at least 4 cores)
    • more memory (RAM) (at least 8GB, preferably 16GB+)

    More memory and cores will help you with compiling and running your code.

    And make sure you take regular backups! You never know when your disk will fail.

    Also make sure to check linux compatibility before you buy. Laptops used to be a pain (10+ years ago), and it’s gotten a lot better, but it’s not always perfect. Just search for “[brand] [model] linux” or try to find the model on the archlinux wiki.



  • Exactly, ansible is basically imperative, where write the steps declaratively.

    Whereas nixos is more like a compiler that compiles to a working linux install.

    If I added the software myprogram and a config file at /etc/myprogram.conf, that’s pretty easy in both. But if I needed to to then remove those it gets different .

    With nixos it’s at easy as removing the two lines that add the program and the config file; after the next “compile”, the file is gone and myprogram is no longer available in the PATH.

    With ansible you need to change the relevant step to use apt remove instead of apt install and to change the config file step in a step that removes the file.

    Don’t get me wrong, ansible is still better than writing a lot of bash scripts, especially if you don’t have people with a lot of shell experience.

    But tools like nixos and guix are on a whole other level.



  • because bash isn’t always in /usr/bin/bash.

    On macOS the version on /usr/bin/bash is very old (bash 3 I think?), so many users install a newer version with homebrew which ends up in PATH, which /usr/bin/env looks at.

    Protip: I start every bash script with the following two lines:

    #!/usr/bin/env bash
    set -euo pipefail
    

    set -e makes the script exit if any command (that’s not part of things like if-statements) exits with a non-zero exit code

    set -u makes the script exit when it tries to use undefined variables

    set -o pipefail will make the exit code of the pipeline have the rightmost non-zero exit status of the pipeline, instead of always the rightmost command.


  • Maybe your drive(s) fail and you want to reinstall. Then you already have a setup with all your software and config files installed. Just reinstall NixOS and re-apply your configuration (or build your own Install ISO ).
    And if you ever get a new laptop/desktop/VM/VPS you can do the same.

    Don’t forget to take backups, regardless of your setup tho.

    The reproducibility also leads to some surprise features, like being able to wipe your entire system on every boot. Since NixOS always puts the necessary files in the correct place, this is perfectly fine. If you then add some mechanism to persist specific data across reboots (a separate partition, or the Impermanence module), you will remove all kinda of randomly accumulated files on every boot.

    This means I have very small backups, because I have three kinds of data: stuff that is wiped on every boot, stuff that is persisted but not backed up (/nix/store, all kinds of caches) and stuff that is persisted and backed up (documents, repositories, media).

    None of my OS’s files are in the backups, which makes of them a lot smaller than my previous arch install.








  • To expand a little on @Laser ‘s point 2:

    In bash (and other programming languages) # is used at the start of the line to notate comments.

    When writing percentages, you write the symbol after the number, e.g. 50%

    That’s how I keep them apart, lol

    Theres a section in the bash manual with these and a whole bunch of more expansion tricks.

    One I find useful is

    echo "${myvar@A}"