安装OpenSSH后SSH连接localhost遇连接重置问题如何解决？

Let’s work through this issue step by step—this error typically indicates the SSH server isn’t accessible for one of a few common reasons. Here’s what to check:

• Verify the SSH server is running
  First, make sure the sshd service is up and running. Run this command to check its status:
  systemctl status sshd
  (If you’re on an older system without systemd, use service ssh status instead.)
  If it shows "inactive" or "failed", start the service with:
  systemctl start sshd
  To ensure it starts automatically on boot, run:
  systemctl enable sshd

• Check if port 22 is allowed through the firewall
  Your firewall might be blocking incoming connections on port 22.
  For ufw (common on Ubuntu/Debian), check the status with:
  ufw status
  If "OpenSSH" isn’t listed as allowed, add the rule:
  ufw allow ssh
  For iptables, add a rule to allow TCP traffic on port 22:
  iptables -A INPUT -p tcp --dport 22 -j ACCEPT
  Don’t forget to save the iptables rules afterward (try iptables-save > /etc/iptables/rules.v4 on Debian/Ubuntu).

• Inspect the SSH server configuration
  A misconfigured sshd_config file can cause connection resets. Open the file with your editor:
  sudo nano /etc/ssh/sshd_config
  Check these key settings:

  • ListenAddress: Should be set to 0.0.0.0 (to listen on all interfaces) or explicitly include 127.0.0.1
  • PasswordAuthentication: Ensure this is set to yes (unless you’re using SSH keys and have that configured properly)
  • PermitRootLogin: If you’re trying to connect as root, make sure this isn’t set to no (though it’s safer to use a regular user)
  • AllowUsers: If this line exists, confirm your user is listed here (e.g., AllowUsers your_username)
    After making changes, restart the SSH server:
    systemctl restart sshd

• Check if port 22 is being used by another process
  Sometimes another application might be occupying port 22. Use this command to see what’s listening on port 22:
  ss -tulpn | grep 22
  If you see a process other than sshd using the port, either stop that process or change the SSH port in sshd_config (set Port to something like 2222, restart the service, then connect with ssh user@localhost -p 2222).

• Check SELinux (if you’re using it)
  SELinux can block SSH connections even if the firewall is open. First, check its status:
  getenforce
  If it returns "Enforcing", try temporarily disabling it to test:
  setenforce 0
  If the connection works after this, you’ll need to update SELinux rules to allow SSH. For example, to ensure port 22 is labeled correctly:
  semanage port -a -t ssh_port_t -p tcp 22
  Then re-enable SELinux with setenforce 1.

• Look at SSH server logs for specific errors
  The logs will give you detailed info about why the connection is being reset. Run this command to tail the auth logs:
  tail -f /var/log/auth.log
  (On RHEL/CentOS, the log is /var/log/secure.)
  Try connecting again while watching the logs—you’ll see exactly what’s failing (e.g., authentication issues, configuration errors).

内容的提问来源于stack exchange，提问作者Shehan Ekanayake