diff --git a/README.md b/README.md
index 8cd3662d..145b8c9e 100644
--- a/README.md
+++ b/README.md
@@ -57,10 +57,13 @@ currently there are two self-contained binaries:
 * `copyparty-sfx.sh` for unix (linux and osx) -- smaller, more robust
 * `copyparty-sfx.py` for windows (unix too) -- crossplatform, beta
 
-launch either of them and it'll unpack and run copyparty, assuming you have python installed of course
+launch either of them (**use sfx.py on systemd**) and it'll unpack and run copyparty, assuming you have python installed of course
 
 pls note that `copyparty-sfx.sh` will fail if you rename `copyparty-sfx.py` to `copyparty.py` and keep it in the same folder because `sys.path` is funky
 
+
+## sfx repack
+
 if you don't need all the features you can repack the sfx and save a bunch of space; all you need is an sfx and a copy of this repo (nothing else to download or build, except for either msys2 or WSL if you're on windows)
 * `724K` original size as of v0.4.0
 * `256K` after `./scripts/make-sfx.sh re no-ogv`
diff --git a/docs/notes.sh b/docs/notes.sh
index ba66ff2e..9a62fc17 100644
--- a/docs/notes.sh
+++ b/docs/notes.sh
@@ -113,3 +113,12 @@ function convert_markdown(md_text, dest_dom) {
         var end = tsh.slice(-2);
         console.log("render", end.pop() - end.pop(), (tsh[tsh.length - 1] - tsh[0]) / (tsh.length - 1));
     }
+
+
+##
+## tmpfiles.d meme
+
+mk() { rm -rf /tmp/foo; sudo -u ed bash -c 'mkdir /tmp/foo; echo hi > /tmp/foo/bar'; }
+mk && t0="$(date)" && while true; do date -s "$(date '+ 1 hour')"; systemd-tmpfiles --clean; ls -1 /tmp | grep foo || break; done; echo "$t0"
+mk && sudo -u ed flock /tmp/foo sleep 40 & sleep 1; ps aux | grep -E 'sleep 40$' && t0="$(date)" && for n in {1..40}; do date -s "$(date '+ 1 day')"; systemd-tmpfiles --clean; ls -1 /tmp | grep foo || break; done; echo "$t0"
+mk && t0="$(date)" && for n in {1..40}; do date -s "$(date '+ 1 day')"; systemd-tmpfiles --clean; ls -1 /tmp | grep foo || break; tar -cf/dev/null /tmp/foo; done; echo "$t0"
diff --git a/scripts/sfx.py b/scripts/sfx.py
index e5a3647e..9ed1fe32 100644
--- a/scripts/sfx.py
+++ b/scripts/sfx.py
@@ -426,6 +426,16 @@ def run(tmp, py):
     msg("will use:", py)
     msg("bound to:", tmp)
 
+    # "systemd-tmpfiles-clean.timer"?? HOW do you even come up with this shit
+    try:
+        import fcntl
+
+        fd = os.open(tmp, os.O_RDONLY)
+        fcntl.flock(fd, fcntl.LOCK_EX | fcntl.LOCK_NB)
+        tmp = os.readlink(tmp)  # can't flock a symlink, even with O_NOFOLLOW
+    except:
+        pass
+
     fp_py = os.path.join(tmp, "py")
     with open(fp_py, "wb") as f:
         f.write(py.encode("utf-8") + b"\n")