Git
How to Set Up SSH Keys for GitHub and GitLab the Safe Way
Set up SSH keys for GitHub and GitLab: generate an Ed25519 key, add it to the agent, upload the public key, test the connection, and use one key per host.
6 min read
Topic
SSH and Networking
SSH keys and tunnels, curl, DNS lookups and port checks, for when a connection will not come up.
Debugging
How to Debug SSH Authentication Problems in Real Scripts
Debug SSH authentication in scripts: BatchMode, verbose output, agent and key selection, known_hosts, server logs and what differs from your terminal.
6 min read
SSH and Networking
SSH Too Many Authentication Failures Error Causes and Fixes
Fix SSH Too many authentication failures: the agent offers every key, MaxAuthTries runs out, IdentitiesOnly and IdentityFile fix it, and how to see the order.
6 min read
SSH and Networking
SSH Remote Host Identification Has Changed Warning
Handle the SSH warning about a changed host identification: legitimate causes, verifying the new key, and removing the old entry with ssh-keygen -R.
6 min read
Debugging
How to Debug DNS and TLS Problems From the Terminal
Debug DNS and TLS problems from the terminal: dig, getent and resolvectl for names, openssl s_client and curl -v for handshakes, with a layered approach.
6 min read
SSH and Networking
SSH Connection Timed Out and Firewall Problems Fully
Fix SSH Connection timed out: tell it from refused, trace the path with nc and traceroute, check firewalls and security groups, and set ConnectTimeout.
6 min read
SSH and Networking
SSH Connection Refused and What to Check First Explained
Fix SSH connection refused: confirm sshd is running and listening, the port and address, firewall rules, and how it differs from a timeout.
6 min read
SSH and Networking
SSH Permission Denied Publickey Causes and Fixes Fully
Fix SSH Permission denied (publickey): read ssh -v output, check the key, the agent, file permissions on both sides, the user name and sshd logs.
6 min read
SSH and Networking
SSH Subsystem Request Failed on Channel 0 With sftp
Fix SSH subsystem request failed on channel 0 with sftp or scp: a missing Subsystem line, wrong sftp-server path, shell startup output and chroots.
6 min read
SSH and NetworkingGuide
SSH From the Basics to a Hardened and Scripted Setup
An SSH guide from first login to a hardened, scripted setup: keys, config files, agents, tunnels, jump hosts, sshd hardening, automation and troubleshooting.
36 min read
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