AdBlocking on Sailfish OS via /etc/hosts

There are some apps in Openrepos which do not seem to work anymore for SFOS 4.x. But you don't really need an app, all you need is a systemd timer & service and a simplistic shell script.

Gain command line access to your phone and become root.

console
> cd /etc/systemd/system
> nano hosts.timer hosts.service
> systemctl daemon-reload
> systemctl enable hosts.timer

hosts.timer:

ini
[Unit]
Description=Update /etc/hosts

[Timer]
WakeSystem=false
OnCalendar=Sat *-*-* 16:00:00
RandomizedDelaySec=1h
AccuracySec=1h
Persistent=true

[Install]
WantedBy=timers.target

So once a week on Saturday at roughly 16:00. Adjust to your liking.
See man systemd.timer for further options.

hosts.service:

ini
[Unit]
Description=Update /etc/hosts

[Service]
# Un/comment as required:
#ExecStart=/home/defaultuser/.local/bin/hosts
ExecStart=/home/nemo/.local/bin/hosts

~/.local/bin/hosts:

bash
#!/bin/bash

# see https://github.com/StevenBlack/hosts/ for alternatives
url="https://raw.githubusercontent.com/StevenBlack/hosts/master/alternates/fakenews-gambling-porn-social/hosts"

cd /etc || exit 1

curl --retry 20 --retry-all-errors --retry-connrefused --retry-delay 5 "$url" | grep '^0\.0\.0\.0' > hosts.new || exit 1
sed -i '/0\.0\.0\.0 0\.0\.0\.0/d' hosts.new

cat hosts.editable hosts.new > hosts.tmp && mv hosts.tmp hosts && rm hosts.new

The script removes some useless fluff and then combines this data with hosts.editable into the new hosts file.
/etc/hosts is only overwritten when all this succeeds.

Make sure that

~/.local/bin/hosts is marked executable: chmod +x ~/.local/bin/hosts
The file /etc/hosts.editable exists and contains the default contents of /etc/hosts (before any manipulation). Here it is:
```
  127.0.0.1       localhost.localdomain localhost
  ::1     localhost6.localdomain6 localhost6
```

Caveat

It seems that a full reboot is required for the new hosts file to take effect for the sailfish-browser.

Android App Support

It also works for Android Apps, explained here:

console
> mv /system/etc/hosts /system/etc/hosts.old
> echo 'lxc.mount.entry = /etc/hosts system/etc/hosts none bind,create=file 0 0' >> /var/lib/lxc/aliendalvik/extra_config