[Technology] systemd timers and service files in place of cron

I keep a daily journal in an Emacs org-mode file.  Sometimes due to clumsy keypresses in Emacs, I have temporarily deleted (!) lines or sections (!).  I think I have always caught these mistakes, but to be safe, I decided to create a git repository for it and do a daily commit.

In the past, I'd have used a cron job, but in recent years I've tried to make more and more use of systemd and timers.  Is one better than the other?  I'm going to ignore that question and proceed. :D

For this task, which I'm calling "log_git_committer" (very uninspired), I have four files:

  • log_git_committer.sh - a Bash script that handles actually committing changes
  • log_git_committer.service - a systemd service file that references the .sh file
  • log_git_committer.timer - a systemd timer file that implicitly references .service unit and describes the interval
  • Makefile - a simple make file to install and uninstall my files as I work on it

Below are some of the more interesting notes from working on it, and the systemd files. 


Some notable pieces that came up:

  • .service:
    • Type=oneshot: since I'm running this from a timer, I just want this service unit to be a "oneshot", as it's not actually a service that would keep running in the background.
    • ExecStart= and %h: I'm installing the shell script locall in my ~/.local/bin directory.  ExecStart in a .service won't accept ~/ or $HOME/ in a path, preferring absolute paths.  However, systemd has some specifiers like %h that will substitute in a user's path when a service unit is run with --user. 
  • .timer:
    • OnCalendar=: it has a lot of options that are similar to cron.  Neat. 
    • retroactively running missed timers?  Yes, if I set a timer to run at 3AM but I put my computer to sleep at 1AM and turn it back on at 8AM, the timer will then execute.  If I end up in Narnia and my computer is asleep for 3 days while I'm away (a lifetime there), it will then run the service just once to catch up.  Nice.
  • Makefile:
    • unit file syntax checking: systemd provides a command that lets you analyze your unit files to check for correctness. E.g.
      systemd-analyze verify log_git_committer.timer
      systemd-analyze verify log_git_committer.service

      so I added that to a target.
    • systemd install directory: for non-root user services and timers, the install directory is ~/.config/systemd/user/
      Some other locations on my Fedora 38 system for systemd unit files include:
      • /usr/lib/systemd/user/
      • /usr/lib/systemd/service/
      • /etc/systemd/user/
      • /etc/systemd/system/
    • systemd and reloading updated .service files: if I make a change to a .service file, systemd would like me to reload the new one from disk.  So, in my Makefile, after I copy .service and .timer files into their install directory, I call:
      systemctl --user daemon-reload


If there's interest, I can share this, but it's pretty simple and straight forward.


Description=Commit changes to a log file




Description=Do a daily commit of the log file.





[Technology] web development: TypeScript!

I used to be a snob about various technologies.  Two decades ago, I hated doing web development with JavaScript, dealing with browser quirks and what felt like deficiencies in the base standard and browser client libraries.  It felt like you couldn't write simple, safe and predictable code, especially without relying on a third party framework or library.

However, much has changed and I genuinely enjoy it now.  I still often prefer to write code without third-party libraries or frameworks if I can afford to, but I have increasingly come to rely on TypeScript.  I value type checking a lot, especially as projects grow and APIs evolve.  Managing types explicitly entails more work earlier on, but it also helps spare me from silly bugs and saves me time during refactoring or when revisiting code I wrote a while ago.  

TypeScript works by transcompiling TypeScript (in .ts files) into pure JavaScript.  Some of my favourite features include:

  • getting to set language standard targets in configuration.  E.g. setting your target to "es2016" will mean the generated JavaScript will down-compile newer syntax into syntax that exists in ECMAScript 2016.  (Note: this doesn't polyfill API functionality!)
  • easily defining interface types for simple objects with fixed property names

There's some effort to promote a native static type system in future ECMAScript, like this proposal: https://github.com/tc39/proposal-type-annotations.  I hope for this friendlier future.


[Technology] firejail: sandboxing with Linux namespaces

I am generally fairly wary of the amount of access software has on my computer.  Consequently, I like to use firejail on Linux to sandbox a lot of applications.  E.g. am I playing a single-player game from itch.io?  It doesn't need access to my mount points, my home directory (beyond the game's own directory for the program, game files and save data) or to the network.  Sometimes I am stunned by how much trust I put into random software back in 1998

It uses Linux namespace and seccomp-bfp.

An example command of what I might use would be:

$ firejail --net=none --disable-mnt --whitelist=/home/myuser/files/games/game_title/ ./game.sh
Some common programs have pre-existing profiles defined by firejail, like firefox, and those can be found in /etc/firejail.  In the case of firefox, one notable change is access to your home directory: it gets restricted to just your downloads folder!


[Technology] Blogger template: add back the edit button

Like poor Blogger user User 7100044714607836407, I have missed the quick edit button on newer Blogger templates. So I wrote a little snippet of JavaScript to bring it back.


  • Appears in the title instead of at the bottom.
  • Does not appear until you press ctrl-e.
  • In theory will show even when readers press ctrl-e, but of course they would still need to log in as you to actually get to the edit page.
  • Just uses the blog and post IDs already viewable on the page.


  window.addEventListener ("keydown", function (ev) {
    if (ev.code == "KeyE" && ev.ctrlKey == true) {
      let posts = document.querySelectorAll ("DIV.post-outer:not(.edit_link_added)") ?? [];
      for (let post of posts) {
        const blog_id = post.querySelector("meta[itemprop='blogId']").getAttribute ("content");
        const post_id = post.querySelector("meta[itemprop='postId']").getAttribute ("content");
        const post_title_h3 = post.querySelector (".post-title");

        let edit_a = document.createElement ("A");
        edit_a.href = `https://www.blogger.com/post-edit.g?blogID=${blog_id}&postID=${post_id}&from=pencil`;
        edit_a.target = "_blank";
        edit_a.innerText = "[✏]";
        post_title_h3.appendChild (edit_a);

        post.classList.add ("edit_link_added");


[Technology] Memento: estate possession distribution


A while ago, I lost a dear family member.  It was a very challenging time, and a very important and heavy activity was helping box up their life, room by room.  There were a lot of memories tied to the physical possessions, and it was hard to make decisions for them at the time, so off they went to storage.

It's been long enough that the beneficiaries need to make collective decisions as to the disposal and distribution of the possessions (storage isn't cheap!)   So, as a fun personal project and an exercise in simple web development, I wrote Memento, which generates tables from a catalogue of photos to allow a group of people to vote on actions for each item.  

 As an example, imagine the beneficiaries are the characters from Scott Pilgrim vs. the World and the possessions are heirloom doughnuts that had been scattered across a couple cities (rather than rooms):


If you find this and find it useful, or are interesting in using it and need some help setting it up, let me know.


[GNOME] GNOME Files and custom file icons: setting a cute 2x2 image preview for photo albums

Update: credit to David in the comments of my previous post, there's a much fancier implementation of this here: https://github.com/flozz/cover-thumbnailer

Going further in my delight at belatedly discovering the "metadata::custom-icon" GVFS attribute used by Nautilus, I extended beyond just music album covers to write a script that did a fun 2x2 grid for photo album covers.

From this:

To this:

This script is uglier, so maybe write your own, but you can have a look-see to see what I did. I learned some new syntax for ImageMagick in the process (using ^ when scaling to treat the geometry as a minimum rather than a maximum, using "-gravity center" to crop from the center, etc.),


# Run in a directory containing photo album folders.  Will generate 2x2 grid thumbnail images of photos within, and set them as the
# folder icon.  (Recurses down through all subfolders.)

# set GVFS attribute "metadata::custom-icon"
# e.g. gio set /path/to/album/dir "metadata::custom-icon" "file:///home/USER/files/music/ARTIST NAME/ALBUM NAME/cover.jpg"
# to reset it:
#      gio set /path/to/album/dir "metadata::custom-icon" -d

function crop {
    DIM="${2}";  # e.g. "200x200"

    # scale so that the min-dimension is 200 (we'll crop out whatever exceeds it in the max dimension)
    # so if we're given an 400x1000 photo here, we'll scale it to 200x500, thanks to ^
    convert "${FILE}" -scale "${DIM}+0+0^" "${FILE}.scaled";

    # crop a 200x200 square from the center, so if we have a 200x500, we'll lose the top and bottom 50
    convert "${FILE}.scaled" -gravity center -crop "${DIM}+0+0" "${FILE}.cropped"
    # now we have a nice 200x200 version, centered

    # emit the name of the newly cropped file
    echo "${FILE}.cropped";

# provide a '-f' option to regenerate existing photo album covers; by default, it skips dirs where one already exists
if [ "${1}" == -f ]; then

find ./ -type d |
    while read DIR; do
        # skip . hidden directories
        if basename "${DIR}" | grep "^\."; then

        echo "${DIR}...";
        # check if a generated photo album already exists and skip redoing it (unless -f set)
        if [ -f "${DIR}/.npac_cover.jpg" ] && [ "${FORCE}" -eq 0 ]; then
            echo "    Already generated, skipping (use -f to force regeneration)";

        # create a temporary directory to do image cropping and stitching in
        TMPDIR="$(mktemp -d)";

        # find 4 images below dir for potential thumbnailing; use 'sort -R' to randomize the list
        find "${DIR}" -regextype egrep -iregex ".*\.(jpg|jpeg|png|webp)$" |
            sort -R |
            while read COVER_PART; do
                # because I sometimes have duplicate files for various reasons, and 
                # I don't want an image repeated, I work with them using their hash
                HASH="$(md5sum "${COVER_PART}" | cut -b 1-32)";

                if ! [ -f "${TMPDIR}/${HASH}" ]; then
                    echo "    ${COVER_PART}";
                    cp "${COVER_PART}" "${TMPDIR}/${HASH}.part"

                if [ "$(ls "${TMPDIR}" | wc -l)" -ge 4 ]; then

        # lets create a 2x2 grid of 4 images, but also support fewer if necessary
            cd "${TMPDIR}";
            NUM_PARTS="$(ls | wc -l)";
            P1="$(ls | head -n 1 | tail -n 1)";
            P2="$(ls | head -n 2 | tail -n 1)";
            P3="$(ls | head -n 3 | tail -n 1)";
            P4="$(ls | head -n 4 | tail -n 1)";

            if [ "${NUM_PARTS}" -ge 3 ]; then
                # stitch the first two together side-by-side for the top half of a 3 or 4 grid
                convert "$(crop "${P1}" 200x200)" "$(crop "${P2}" 200x200)" -background black +append "top.jpg"

                if [ "${NUM_PARTS}" -ge 4 ]; then
                    # stitch two together for the bottom, then stitch top and bottom together for the grid, yay
                    convert "$(crop "${P3}" 200x200)" "$(crop "${P4}" 200x200)" -background black +append "bottom.jpg"
                    convert "top.jpg" "bottom.jpg" -background black -append "grid.jpg"
                elif [ "${NUM_PARTS}" -eq 3 ]; then
                    # only have 3 images, so make the 3rd one take up the whole bottom
                    convert "top.jpg" "$(crop "${P3}" 400x200)" -background black -append "grid.jpg"
            elif [ "${NUM_PARTS}" -eq 2 ]; then
                # only have two, so stack them vertically
                convert "$(crop "${P1}" 400x200)" "$(crop "${P2}" 400x200)" -background black -append "grid.jpg"
            elif [ "${NUM_PARTS}" -eq 1 ]; then
                # only have one, so it'll be the whole grid!
                cp "$(crop "${P1}" 400x400)" grid.jpg
                echo "WARNING: nautilus_photo_album_cover.sh: no images found for dir '${DIR}' in tmpdir '${TMPDIR}'.";

        # if we successfully generated a grid of images, copy it to the photo album dir as a 
        # hidden thumbnail image (.npac_cover.jpg), set "metadata::custom-icon" in GVFS, and then remove the temp dir
        if [ -f "${TMPDIR}/grid.jpg" ]; then
            cp "${TMPDIR}/grid.jpg" "${DIR}/.npac_cover.jpg"
            gio set "${DIR}" metadata::custom-icon "file://$(realpath "${DIR}/.npac_cover.jpg")";
            rm -rf "${TMPDIR}"

To do:

  • Add a cute folder emblem to the bottom right of the 2x2 icons, and maybe put a border around it, to make it more obviously still a folder!
  • It fails on some folders for some reason, look into it :D
  • Correct orientation issues


[GNOME] GNOME Files and custom file icons: setting album art on directories!

Update: credit to David in the comments, there's a much fancier implementation of this here: https://github.com/flozz/cover-thumbnailer

While playing with GNOME 43 on my recent upgrade to Fedora 37, I saw that nautilus aka GNOME Files lets me set arbitrary images as a custom icon for files and folders, replacing the default icon/thumbnail.  (The support for "metadata::custom-icon" has apparently been around for a while already.)

I quickly hopped into my music folder and wrote a small script to replace all of the (legally purchased) folders of albums of music's icons with images of their album art if an image was already present.

 My Camera Obscura band's folder of albums went from this:

to this


The quick code:


find ./ -type d |
    while read DIR; do
        if basename "${DIR}" | grep "^\."; then
            # skip . directories

        echo "${DIR}...";
        touch /tmp/.naa.coversearch

        # ranked cover options by preference, as some dirs have multiple; 
        # break after we find highest one
        echo "front.(jpg|png)
album\-[0-9a-f]+\-[0-9a-f]+\.jpeg" |
            while read COVER_PATTERN; do
                # echo "  ${COVER_PATTERN}...";

                find "${DIR}" -regextype egrep -regex ".*/${COVER_PATTERN}$" |
                    head -n 1 | # grab first and go            
                    while read COVER_RELPATH; do
                        rm /tmp/.naa.coversearch # we found a cover, end search

                        echo "    found cover ${COVER_RELPATH}!";
                        COVER_ABSPATH="$(realpath "${COVER_RELPATH}")";
                        gio set "${DIR}" metadata::custom-icon "file://${COVER_ABSPATH}"

                # if we're not still searching, skip other patterns and go to next dir
                test -f /tmp/.naa.coversearch || break 

For the curious, I purchased a lot of legally-licensed, DRM-free music through eMusic back in the day, before streaming took over everything. I still purchase CDs as merch at shows sometimes, and then extract those to OGG Vorbis (sorry, not FLAC). Sometimes, I still open up Rhythmbox and play actual files, ooo.

To do:

  • corner folder icons: Generate album folder thumbnails that have a little folder icon in the bottom corner still, so I can tell that it's still a folder
  • artist custom icons as potential grids: My folder structure is artist/album/track.ogg. So right now, the artist folder also acquires the first album cover it finds. If an artist has multiple album covers available, I want to do a small grid of up to 2x2.
  • photo albums: do something similar for photo albums folders.

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