[systemd-devel] Question about sysctl persistence

[EpicTux123]

Hello there.

I had the following file in my system:

/etc/sysctl.d/90-custom-mtu-probing.conf
net.ipv4.tcp_mtu_probing=1

I deleted that file and rebooted my system.
But the "net.ipv4.tcp_mtu_probing" value is still "1", even though its default is "0".

I have tried to use "sudo sysctl -w net.ipv4.tcp_mtu_probing=0" and "echo 0 > /proc/sys/net/ipv4/tcp_mtu_probing" (as sudo), but it still gets reverted to "1" after reboot.

My intention is to go back to its default, which is "0", without having to create a custom override for it (which should be happening).
I have ran "sudo sysctl --system" and it does not appear there. I have checked all system-wide locations for sysctl.d/sysctl.conf files/directories and also nothing there.

The kernel itself is not very clear about the default value of this parameter (I couldn't find it, at least).

Help is appreciated. Thanks.