diff --git a/how_to b/how_to
index a3c7e6f..9553431 100644
--- a/how_to
+++ b/how_to
@@ -218,6 +218,8 @@ PDF :
         Extract pages :
             pdftk input.pdf cat <range> output out.pdf
             # range can be <start>-<end>, more info at pdftk --help
+        Uncompress pdf file content :
+            pdftk input.pdf output output.pdf uncompress
     Add images and other files in a single pdf:
         convert [jpg|png|txt|pdf|...] output.pdf
         # Might need to tweak /etc/ImageMagick-7/policy.xml
@@ -225,6 +227,8 @@ PDF :
     Fill form & annotate:
         For well formatted interactive forms:
             evince
+        For Adobe type forms (AcroForm / XFA):
+            pdfjs  # (supports forms since 2.6.347 / firefox 81)
         For non-interactive PDF:
             xournal
             libreoffice Draw
@@ -370,6 +374,16 @@ Video and audio editing:
         xdotool selectwindow getwindowgeometry | awk '/Position/{printf $2" "$4" "} /Geometry/{printf $2" "}' | sed 's/)//' | read OFFSET SCREEN SIZE; ffmpeg -video_size $SIZE -framerate 30 -f x11grab -i "$DISPLAY.$SCREEN+$OFFSET" -vf "scale=2*trunc(iw/2):-2,setsar=1" -pix_fmt yuv420p out.mp4
     Filter doc:
         # https://trac.ffmpeg.org/wiki/FilteringGuide
+    Create captioned gif from mp4:
+        # https://nickcanzoneri.com/ffmpeg/gif/2018/11/20/captioned-gifs-with-ffmpeg.html
+        # https://stackoverflow.com/a/14283648  // recale
+        # https://video.stackexchange.com/a/20106  // font style
+        text.srt:
+            1                               # Sequence number
+            00:00:00,000 --> 00:00:01,900   # Start and end timestamps
+            Your text here                  # Actual text
+                                            # Mandatory empty line
+        ffmpeg -i in.mp4 -vf "scale=512:-2:flags=lanczos,split[x][z];[z]palettegen[y];[x][y]paletteuse,subtitles=text.srt:force_style='FontName=Oswald,Fontsize=80,FontWeight=Bold'" -r 10 out.gif
 
 ImageMagick:
     crop to aspect ratio
@@ -402,13 +416,23 @@ Mount as user:
     sudo chown <user> /mnt
 
 Borg backup:
-    borg init --encryption=repokey-blake2 </repo>
-    borg create -v --stats --progress --compression zlib "/mnt/<machine>/home/::{now}" /home/<user>
+    # Example repo: /mnt/<machine>/home
+    # Dry run: -n
+    # Avoid mixing users in single repo (don't create archives from different users in a single repo)
+    [sudo] borg init --encryption=repokey-blake2 </repo>
+    borg create -v --stats --progress --compression zlib --exclude ~/.local/share/Steam "</repo>::{now}" /home/<user>
+    sudo borg create -v --stats --progress --compression zlib "</repo>::etc-{now}" /etc
+    sudo borg create -v --stats --progress --compression zlib --exclude /var/cache --exclude /var/tmp "</repo>::var-{now}" /var
     borg list </repo>
     borg check --verify-data --progress </repo>
     borg mount </repo> </mount>
     borg prune -v --list --keep-daily=7 --keep-weekly=4 --keep-monthly=6 </repo>
 
+    # Restoring
+    borg list </repo>
+    borg mount </repo>::"<name>" /mnt/borg
+    borg umount /mnt/borg
+
 Serial terminal
     st -l /dev/ttyUSB0 <baud>
 
@@ -564,6 +588,8 @@ Maildir tweaking:
         for f in new/*; do mv "$f" "cur/${f##*/}:2,S"; done
         # ${f##*/} removes path prefix.
         # ":2,S" is a maildir suffix (S=seen)
+    Cleanup maildir folder after messing around (requires mblaze):
+        mlist <folder> | mrefile <folder>
 
 Install 64 bits kernel on 32 bits system (and 64 bits hardware) (bad idea)
     wiki.archlinux.org/index.php/Migrating_between_architectures
@@ -892,3 +918,51 @@ MacOS survival guide (Because the "user friendly" OS has worse affordances than
         Release <Alt>
     Maximizing window WITHOUT fullscreen
         Double click window title bar
+
+Mounting .bin/.cue image files:
+    $ sudo pacman -S bchunk
+    $ bchunk file.bin file.cue output
+    $ sudo mount output01.iso /mnt -o loop,ro
+
+Manual IMAP connection:
+    # https://www.atmail.com/blog/imap-101-manual-imap-sessions/
+    # https://stackoverflow.com/questions/14959461/how-to-talk-to-imap-server-in-shell-via-openssl
+
+    $ openssl s_client -connect <imap server>:993 -crlf [-quiet]
+    $ openssl s_client -connect <imap server>:143 -crlf -starttls imap [-quiet]
+    # IMAP needs an incrementing prefix before each command
+    A1 login <login> "<password>"
+    # list everything
+    A2 list "" "*"
+    # list everything under a particular prefix
+    A3 list "INBOX" "*"
+    A99 logout
+
+gdb tricks:
+    Easily print attributes of array elements:
+        # https://agateau.com/2008/gdb-trick-the-poor-man-loop
+        (gdb) set $pos = 0
+        (gdb) print foo[$pos++].attribute
+        (gdb) <enter>
+        (gdb) <enter>
+        ...
+    Or use a real loop:
+        (gdb) set $i = 0
+        (gdb) while ($i < <length>)
+        > print foo[$i++].attribute
+        > end
+
+Non-standard zsh cd trick:
+    # https://dataswamp.org/~solene/2020-09-04-cd-command.html
+    $ pwd
+    /tmp/pobj/foobar-1.2.0/work
+    $ cd 1.2.0 2.4.0
+    /tmp/pobj/foobar-2.4.0/work
+
+Check for available package updates with Arch/Artix:
+    sudo pacman -S pacman-contrib
+    checkupdates
+
+Git push and pull using different URL/protocols:
+    # https://www.scivision.dev/git-pull-https-push-ssh/
+    git config url."git@example.org:user/".pushInsteadOf "https://example.org/user/"