This is part of a series of posts on compiling a custom version of Qt5 in order
to develop for both amd64 and a Raspberry Pi.
Building Qt5 takes a long time. The build server I was using had CPUs and RAM,
but was very slow on I/O. I was very frustrated by that, and I started
evaluating alternatives. I ended up setting up scripts to automatically
provision a throwaway cloud server at
Hetzner.
Initial setup
I got an API key from my customer's Hetzner account.
I installed
hcloud-cli, currently only in testing and unstable:
Then I configured
hcloud with the API key:
Spin up
I wrote a quick and dirty script to spin up a new machine, which grew a bit
with little tweaks:
#!/bin/sh
# Create the server
hcloud server create --name buildqt --ssh-key --start-after-create \
--type cpx51 --image debian-10 --datacenter
# Query server IP
IP="$(hcloud server describe buildqt -o json jq -r .public_net.ipv4.ip)"
# Update ansible host file
echo "buildqt ansible_user=root ansible_host=$IP" > hosts
# Remove old host key
ssh-keygen -f ~/.ssh/known_hosts -R "$IP"
# Update login script
echo "#!/bin/sh" > login
echo "ssh root@$IP" >> login
chmod 0755 login
I picked a datacenter in the same location as where we have other servers, to
get quicker data transfers.
I like that CLI tools have JSON output that I can cleanly pick at with
jq. Sadly, my ISP doesn't do IPv6 yet.
Since the server just got regenerated, I remove a possibly cached host key.
Provisioning the machine
One git server I need is behind HTTP authentication. Here's a quick hack to
pass the relevant
.netrc credentials to ansible before provisioning:
#!/usr/bin/python3
import subprocess
import netrc
import tempfile
import json
login, account, password = netrc.netrc().authenticators(" ")
with tempfile.NamedTemporaryFile(mode="wt", suffix=".json") as fd:
json.dump(
"repo_user": login,
"repo_password": password,
, fd)
fd.flush()
subprocess.run([
"ansible-playbook",
"-i", "hosts",
"-l", "buildqt",
"--extra-vars", f"@ fd.name ",
"provision.yml",
], check=True)
And here's the ansible playbook:
#!/usr/bin/env ansible-playbook
- name: Install and configure buildqt
hosts: all
tasks:
- name: Update apt cache
apt:
update_cache: yes
cache_valid_time: 86400
- name: Create build user
user:
name: build
comment: QT5 Build User
shell: /bin/bash
- name: Create sources directory
become: yes
become_user: build
file:
path: ~/sources
state: directory
mode: 0755
- name: Download sources
become: yes
become_user: build
get_url:
url: "https:// / item "
dest: "~/sources/ item "
mode: 0644
with_items:
- "qt-everywhere-src-5.15.1.tar.xz"
- "qt-creator-enterprise-src-4.13.2.tar.gz"
- name: Populate home directory
become: yes
become_user: build
copy:
src: build
dest: ~/
mode: preserve
- name: Write .netrc
become: yes
become_user: build
copy:
dest: ~/.netrc
mode: 0600
content:
machine
login repo_user
password repo_password
- name: Write .screenrc
become: yes
become_user: build
copy:
dest: ~/.screenrc
mode: 0644
content:
hardstatus alwayslastline
hardstatus string '% = cw %-Lw% = KW %50>%n%f* %t% = cw %+Lw%< % = kK %-=%D %Y-%m-%d %c% - '
startup_message off
defutf8 on
defscrollback 10240
- name: Install base packages
apt:
name: git,mc,ncdu,neovim,eatmydata,devscripts,equivs,screen
state: present
- name: Clone git repo
become: yes
become_user: build
git:
repo: https:// @ / .git
dest: ~/
- name: Copy Qt license
become: yes
become_user: build
copy:
src: qt-license.txt
dest: ~/.qt-license
mode: 0600
Now everything is ready for a 16 core, 32Gb ram build on SSD storage.
Tear down
When done:
#!/bin/sh
hcloud server delete buildqt
The whole spin up plus provisioning takes around a minute, so I can do it when
I start a work day, and take it down at the end. The build machine wasn't that
expensive to begin with, and this way it will even be billed by the hour.
A first try on a CPX51 machine has just built the full Qt5 Everywhere
Enterprise including QtWebEngine and all its frills, for
amd64, in under 1
hour and 40 minutes.
This is part of a series of posts on compiling a custom version of Qt5 in order
to develop for both amd64 and a Raspberry Pi.
The previous rounds of attempts ended in 
Those faint white vertical lines one can see, are actually window borders, and
the lock screen is leaking contents of my unlocked desktop! Here is the same
screen, unlocked:
However, moving the windows around does not reflect on the ghost image on top
of the lock screen: reshuffling windows then locking, produces always the same
ghost image. The white border reflects where the window has been at some time
in the past.
The lock screen does not seem to be responsible, either: dragging a solid
colored window on the laptop screen has the same effect:
But taking a screenshot of it does not show the time traveling ghost windows:
This is happening on two different laptops, an HP EliteBook x360 G1, and a
Lenovo ThinkPad X240, one that I've been using since 3 years, one that I've
been using since a week, and whose only thing in common is a 1920x1080 IPS
screen and an Intel GPU.
I have no idea where to start debugging this. Please reach out to me at
enrico@debian.org if any of this makes sense to you.
Update: Jim Paris pointed me to 
