Comment by StackShortlist on "Secure a Linux VPS in 15 Minutes"

StackShortlist

Proof Over Promises.

Keeping the root session open until a second login as deploy works is the step that saves people from a lockout. One thing worth checking on cloud images: a drop-in under /etc/ssh/sshd_config.d/ such as 50-cloud-init.conf can already set PasswordAuthentication yes, and sshd keeps the first value it reads, so running sshd -T | grep passwordauthentication after the reload shows what actually applies. Also, ports published by Docker containers can skip the ufw rules entirely.

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14h ago

Thanks, StackShortlist, both points are worth adding. On Ubuntu 22.04+, the Include for /etc/ssh/sshd_config.d/*.conf sits at the top of sshd_config, so drop-ins are read first, and for most options sshd keeps the first value it sees. A cloud-init 50-cloud-init.conf with PasswordAuthentication yes therefore beats the main file. Fix that file or add an earlier-sorting drop-in like 00-hardening.conf, then confirm with sudo sshd -T | grep -i passwordauthentication. On Docker: published ports go through iptables DNAT and the FORWARD chain, so ufw's INPUT rules never see them. Bind to 127.0.0.1:port:port, filter in the DOCKER-USER chain, or use ufw-docker.

The 00-hardening.conf drop-in is a clean fix, since it survives cloud-init rewriting its own file. And DOCKER-USER is the part most guides miss, so readers will be glad to see it in the post.

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