SSH Keys Broke My First Connection: A Lesson Learned

Hey everyone, welcome back to Oops IT! Today, we’re diving into a classic rite of passage for anyone venturing into the wonderful world of servers and remote access: the dreaded SSH connection failure. I remember my first time trying to SSH into a shiny new VPS. I’d followed all the tutorials, typed in the IP address, the username, hit enter, and… crickets. Well, not exactly crickets, but a very unhelpful error message that made me want to throw my laptop out the window. It was the digital equivalent of knocking on a door and having someone just stare at you blankly.

TL;DR: My SSH keys were messed up. Like, really messed up.

The error message wasn't a screaming siren; it was more of a polite but firm "Nope." Something like:

Permission denied (publickey,password).

Or sometimes, if I was feeling really fancy and had tried to enable password auth:

ssh: connect to host [your_server_ip] port 22: Connection timed out

This latter one was even more frustrating because it implied nothing was happening, which felt worse than a direct rejection. The server was just… ignoring me. I spent hours that first night going through every possible permutation of commands, checking my network, even questioning the very fabric of the internet. Turns out, the culprit was something I thought I’d gotten right: SSH keys.

The Setup: A New Server and a Dream of Remote Access

So, the scenario. I’d just signed up for a cheap VPS – my first step into the "real" server world. I was going to host a personal blog, maybe a little game server, the whole ambitious junior dev dream. The provider’s control panel gave me an IP address, a root password (which I immediately changed, because, you know, security), and a handy guide to setting up SSH access.

The guide said to create an SSH key pair on my local machine and then copy the public key to the server. Simple enough, right? I’d used ssh-keygen before, so I figured I was golden.

ssh-keygen -t rsa -b 4096

This command dutifully spat out a id_rsa (private key) and id_rsa.pub (public key) in my ~/.ssh/ directory. Then came the part about copying the public key. The provider recommended a tool called ssh-copy-id.

ssh-copy-id user@your_server_ip

I entered my server password when prompted, and it seemed to work! It said something about adding the key to ~/.ssh/authorized_keys. Success! Or so I thought.

The next step was to SSH in using my key, not my password. This is the whole point, right? More secure, more convenient. So, I typed:

ssh user@your_server_ip

And then… Permission denied (publickey,password).

Queue the dramatic music.

My mind raced. Did I mistype the IP? No. The username? Nope. Did I forget to install SSH on the server? The provider always includes it. Was the firewall blocking me? I hadn’t even set that up yet!

Deconstructing the Error: It's All About Permissions (and File Locations)

This Permission denied (publickey,password) is a classic. It means SSH tried to authenticate you using your public key, failed, and then tried to fall back to a password, which also failed (or was disabled).

After what felt like an eternity of Googling and re-reading tutorials, I started looking at the server-side configuration and file permissions. This is where the real learning happened.

First, I SSH’d back in using the root password (which I was trying to avoid, but desperate times!). Then, I navigated to the user's home directory on the server. Let’s say my username was devuser.

# On the server, logged in as root
cd /home/devuser/
ls -la

I expected to see a .ssh directory with an authorized_keys file inside. And there it was! But when I checked its permissions, something was off.

# Still on the server
cd .ssh
ls -la

The output looked something like this:

drwxr-xr-x 2 devuser devuser 4096 Jan 15 10:00 .
drwxr-xr-x 5 devuser devuser 4096 Jan 15 09:55 ..
-rw------- 1 devuser devuser  398 Jan 15 10:00 authorized_keys

The critical part here is the permissions for .ssh and authorized_keys.

The .ssh directory needs to be accessible by the user, but not world-writable. The drwxr-xr-x (755) is usually fine. The authorized_keys file needs to be readable by the user, but not world-writable. The -rw------- (600) is ideal.

My mistake? In my haste, I might have accidentally made the .ssh directory or the authorized_keys file too permissive. If the SSH server sees that sensitive files like authorized_keys are writable by others (even inadvertently), it will refuse to use them for security reasons. This is a huge security feature, but it’s a real pain when you’ve messed it up.

The fix involved chmod (change mode) commands on the server:

# On the server, logged in as root or the user
chmod 700 /home/devuser/.ssh
chmod 600 /home/devuser/.ssh/authorized_keys

I also made sure the ownership was correct. If I had created the .ssh directory as root, it would cause issues.

# On the server, logged in as root
chown -R devuser:devuser /home/devuser/.ssh

After applying these permissions, I tried SSHing again from my local machine:

# On your local machine
ssh devuser@your_server_ip

And voila! No password prompt, just a glorious server prompt. It felt like unlocking a secret level.

Beyond Permissions: Other SSH Saboteurs

While permissions were my main nemesis, I learned that SSH connection failures can stem from a surprisingly diverse range of issues. It’s like a tech scavenger hunt!

* Incorrect sshd_config: The SSH daemon configuration file (/etc/ssh/sshd_config on most Linux