Category: Working Notes

Linux Steam: Turning Off DPIScaling
Steam under Linux (and probably other environments too but I’ve never run it elsewhere) has a nice feature to enlarge text on high dpi displays. Unfortunately when I enable it, the pop-up windows (such as the settings window) will scroll down the screen repeatedly disappearing from view.

Which is very inconvenient and makes it quite tricky to turn the feature back off again. Now this could be a problem with the Awesome window manager or with the settings that I use (although Steam seems to be the only application with this issue), but I’m not interested enough to try and fix the problem.

I just want to change the setting back to something that may be small and squashed but at least works.
1. Find the ~/.steam/registry.vdf file.
2. Edit with a text editor and search for “DPIScaling” :-
```
» grep DPIScaling registry.vdf 
					"DPIScaling"		"1"
```
And change the “1” to a “0”, and restart Steam.

About To Break
2021-10-30
Linux Netplan: Making NICs “Optional”
Ever since adding a couple of additional network interfaces to my workstation I have had a problem with reboots – the systemd-networkd-wait-online.service service “lingers” as it waits for all of the NICs to come online (and fails). Not especially problematic as everything works fine after the boot process has finished, but it slows down reboots (which are slow enough on this rather complicated desktop) and gives me an amber ✗ in my window manager’s status bar.

After spending some time re-jigging my storage (which consisted of far too many reboots), I finally decided to fix it.

Which basically consisted of making the relevant NICs “optional” in netplan. :-
```
    enp9s0f1:
      dhcp4: false
      accept-ra: false
      addresses: [172.16.76.0/24]
      optional: true
```
This isn’t one of the NICs that I actually use – I added the NIC configuration in an earlier attempt at making things work … unsuccessfully. The key part is the “optional: true” bit.

And whilst you’re in there, replacing the gatewayv4 and gatewayv6 specifications with the “new style” is worth doing too :-
```
      routes:
        - to: default
          via: 192.0.2.1
        - to: default
          via: 2001:db8:9c2:dead::1
```
(No those aren’t the real addresses)

This can be activated in the usual way – with a netplan apply (in my case a netplan try isn’t effective because of the use of bridges), although in this particular case a full reboot is called for.

The Round Table
2021-10-30
ZFS: Replacing A Functional Mirrored Disk
This is a procedure to replace one working drive in a fully functional mirror vdev; if you are replacing a failed disk there is no advantages in following this procedure. Although if you have a somewhat functional disk it may be worth trying.

So why not simply yank out the working disk you want to replace? Well, you can of course and that would work but there is nothing Murphy likes more than a mirrored vdev temporarily down to a single disk – resilvering onto a new disk guarantees a higher chance of failure of the previously working disk (I have actually seen this happening).

So I’m going to describe how to make a three-way mirror with three disks and then detach the disk you wanted to replace.

To do this there are some prerequisites :-
1. You will need space to install an additional disk into your system; perhaps temporarily in an “unsuitable” location.
2. You will need a spare SATA controller port to plug the new disk into. If necessary with an additional PCIe SATA controller (which sounds expensive but safety is worth the cost).
3. You will need a SATA data cable and a SATA power cable.
The first step is to make very careful note of what devices you are going to “swap over” – ideally using their WWNs. If you don’t use WWNs, sorting out which disk is which is going to be a bit trickier.

The second step is to practice the steps involved using a ‘fake’ storage pool backed up by tiny disk files :-
```
# cd /pool1/temp
# for w in one two three
do
  dd if=/dev/zero of=test-disk-${w}.img bs=1M count=1000
done
# zpool create test mirror /pool1/temp/test-disk-one.img /pool1/temp/test-disk-two.img
# zpool attach test /pool1/temp/test-disk-one.img /pool/temp/test-disk-three.img
# zpool detach test /pool1/temp/test-disk-one.img
```
That’s pretty much it in a nutshell.

The real process is a bit more disturbing of course and most of the work is physical. The first difference from practice is that when you attach the new disk to one or other of the existing devices within the mirror, you will have to wait until the resilvering process is complete.

Whilst you will receive an estimate for that if you run zpool status, the estimate that you get :-
```
  scan: resilver in progress since Sun Jul 18 08:20:54 2021
	8.25T scanned at 1.09G/s, 7.28T issued at 981M/s, 8.25T total
	995G resilvered, 88.23% done, 0 days 00:17:16 to go
```
(Only showing the relevant part as the full output from my system is confusing and deceptive)

Is wildly inaccurate – partially because the resilvering process takes second place to any ordinary file system activity. My own estimate (1 hour per Tbyte) is probably also wildly inaccurate; basically it is done when it is done.

Detaching the old device is fast – you won’t need to sit down to wait for it.
2021-07-18
Re-enabling .xsession
So I am currently messing around with a tiling window manager on my laptop – I prefer tiling window managers in general (I use Awesome on my main desktops). These are (in general) not “desktop environments” but just manage windows (and sometimes a “status bar”).

As it happens the window manager I’m messing with doesn’t come as part of a distribution package with a pre-prepared file for GDM3 to use. So I created a ~/.xsession file – something that has worked since display managers first arrived.

Didn’t work.

Turns out that I need to “hack” GDM3 to make a long standard bit of functionality functional again. As an aside (and especially to the GNOME people), all you had to do to keep this functional was detect if someone had a ~/.xsession file and then offer that up as a menu option. Not that difficult to do and even if it isn’t your preferred way of doing things, it’s a nice thing to do for us old-timers.

Anyway, to restore this functionality all it took was to create a file in //usr/share/xsessions/ called xsession.desktop with the following contents :-
```
[Desktop Entry]
Name=XSession
Comment=This session uses the custom xsession file
Exec=/etc/X11/Xsession
Type=Application
DesktopNames=GNOME-Flashback;GNOME;
X-Ubuntu-Gettext-Domain=gnome-flashback
```
Dead simple.

And yes I stole this and adapted it myself – I’m putting this up here so that I know where to look when I need it again.
2020-07-11
Messing With Rofi: Inserting Unicode
I used to be able to remember all of the keyboard short-cuts I’d set up to insert ‘fun’ (or useful) Unicode characters … but my memory isn’t quite what it used to be, and I happened to catch a video that mentioned a menu to insert Unicode characters.

So I set out to create my own …
```
#!/bin/zsh
#
# Run a menu of Unicode characters to put into the clipboard

read -r -d '' menu << END
Þ       Thorn (Sym-t)
Þ	Capital thorn (Sym-T)
✓	Tick (Sym-y)
✔       Alternate tick (Sym-Y)
π	pi (Sym-p)
Π       PI (Sym-P)
★       Star
🖕      Finger
END

selectedchar=$(echo $menu |\
  rofi -dmenu -l 20 -fn misc-24 -p "Unicode inserter" |\
  awk '{print $1}')
if [ -z "$selectedchar" ]
then
  notify-send "Unicode Inserter" "Cancelled"
else
  printf "%s" $selectedchar | xclip -selection clipboard
  notify-send "Unicode Inserter" \
    "Character $selectedchar now in clipboard"
fi
```
This script :-
1. Creates a variable with a whole pile of text inside it. The original script contains a lot longer list, but including it would be a) boring and b) give too much away. As it stands, the format of each line is pretty much anything you want as long as the first character is the Unicode character followed by whitespace.
2. Runs rofi with the variable as input and selects the first field of the response.
3. Guards against the empty selection (when the menu was cancelled) for neatness mostly.
4. Prints the selected character (without a newline) into xclip so it can be pasted in. I did try using xdotool to type it directly into the active window, but this didn’t always work so well (i.e. xdotool couldn’t “type” some of the more esoteric characters).
5. And uses notify-send to alert the dumb user (me!) that something has happened.
Lastly, to make this useful, I added an entry to my sxhkd configuration :-
```
super + F11
  /site/scripts/m-unicode-insert
```
2020-02-29