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Update anonymizing-your-mac-address.md

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Add random hostname section
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3hhh 2020-01-11 17:17:51 +01:00 committed by GitHub
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external/privacy-guides/anonymizing-your-mac-address.md vendored
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@ -71,3 +71,44 @@ Finally, shutdown all VMs and change the settings of sys-firewall, etc. to use t
You can check the MAC address currently in use by looking at the status pages of your router device(s), or inside the NetVM with the command `sudo ip link show`.
## Randomize your hostname
DHCP requests also leak your hostname to your LAN. Since your hostname is usually `sys-net`, other network users can easily spot that you're using Qubes OS.
Unfortunately `NetworkManager` currently doesn't provide an option to disable that leak globally ([Gnome Bug 768076](https://bugzilla.gnome.org/show_bug.cgi?id=768076)).
You may however use the following code to assign a random hostname to a VM during each of its startup. Please follow the instructions mentioned in the beginning to properly install it.
```.bash
#!/bin/bash
set -e -o pipefail
#
# Set a random hostname for a VM session.
#
# Instructions:
# 1. This file must be placed and made executable as the file /etc/network/if-pre-up.d/00_hostname (owner: root) inside the template VM of your
# network VM.
# 2. Execute `sudo touch /etc/hosts.lock` inside the template VM of your network VM.
# 3. Execute inside your network VM:
# `sudo bash -c 'mkdir -p /rw/config/protected-files.d/ && echo /etc/hosts'"$'\n'"'/etc/hostname > /rw/config/protected-files.d/protect_hostname.txt'`
#NOTE: mv is atomic on most systems
if [ -f "/rw/config/protected-files.d/protect_hostname.txt" ] && rand="$RANDOM" && mv "/etc/hosts.lock" "/etc/hosts.lock.$rand" ; then
name="PC-$rand"
echo "$name" > /etc/hostname
#from /usr/lib/qubes/init/qubes-early-vm-config.sh
if [ -e /etc/debian_version ]; then
ipv4_localhost_re="127\.0\.1\.1"
else
ipv4_localhost_re="127\.0\.0\.1"
fi
sed -i "s/^\($ipv4_localhost_re\(\s.*\)*\s\).*$/\1${name}/" /etc/hosts
sed -i "s/^\(::1\(\s.*\)*\s\).*$/\1${name}/" /etc/hosts
fi
exit 0
```
Assuming that you're using `sys-net` as your network VM, your `sys-net` hostname should now be `PC-[number]` with a different `[number]` each time your `sys-net` is started.
Please note that the above script should _not_ be added to [/rw/config/rc.local](/doc/config-files/)) as that is executed only _after_ the network fully started.