Not so obvious things

tricks.md

Linux things

Fix stupid Docker

Docker daemon messes up iptables configuration.

>/etc/docker/daemon.json cat <<EOF
{
	"iptables": false
}
EOF

Administration

Managing users

Running in musl and busybox environment.

• Do not use addgroup/adduser commands family. Vi is all you need to add another user or group. OK, maybe also openssl to generate password hash.
• You can put comments in passwd, shadow, and groups files!
• It’s safe to delete /etc/securetty. I don’t know why would anyone need TTY restrictions these days anyway.

Networking

Disable priveleged ports on Linux

After reading dozens of shitty iptables, authbind, systemd and xinetd solutions, here is the sysctl option:

# works for IPv6 too
sysctl net.ipv4.ip_unprivileged_port_start=0