Error map
AH00072: make_sock: could not bind to address 0.0.0.0:80 Apache: (98)Address already in use: AH00072: make_sock: could not bind to address [::]:80 / AH00015: Unable to open logs
Nginx / Apache · layer 3, Edge & web server
Centre: this error. First ring: errors it is linked with (12). Outer ring: what those are linked with. Colours show the layer of a request each error belongs to. Click any dot to re-centre the map on it; hover to follow its connections. The centre dot opens the error page.
Directly related (12)
[nodemon] app crashed - waiting for file changes before starting...
Your app threw an error on startup; nodemon is waiting for a file change to retry.
Error: listen EACCES: permission denied 0.0.0.0:80
Node isn’t allowed to bind that port — ports below 1024 need root on Linux/macOS, and some Windows ports are reserved.
Error: listen EADDRINUSE: address already in use :::3000
Another process is already listening on that port.
nginx: [emerg] bind() to 0.0.0.0:80 failed (98: Address already in use)
Nginx (or another server) can’t listen on the port because another process already holds it — often Apache, another Nginx, or a s…
Apache: AH00558: apache2: Could not reliably determine the server's fully qualified domain name
A harmless startup warning: Apache has no global ServerName, so it guessed one from the host’s IP.
Nginx: nginx: [error] invalid PID number "" in "/run/nginx.pid" (when running nginx -s reload)
Nginx can't signal the master process because the PID file is empty, stale or missing.
Apache: AH00112: Warning: DocumentRoot [/var/www/example.com/public_html] does not exist
A virtual host points to a directory that doesn't exist.
Apache: AH00091: apache2: could not open error log file /var/log/apache2/error.log. AH00015: Unable to open logs (Permission denied)
Apache can't open its log files — permissions, a missing directory or disk problems.
Browser shows <?php code or downloads index.php — mod_php / PHP-FPM handler not configured in Apache
Apache serves PHP files as plain text because no PHP handler is active.
systemd: apache2.service: Main process exited, code=exited, status=1/FAILURE — Job for apache2.service failed because the control process exited with error code
systemd couldn't start Apache — the real error is in the journal or `apachectl configtest`.
Nginx: nginx: [emerg] bind() to 0.0.0.0:80 failed (13: Permission denied)
Nginx isn't allowed to bind that port — a privileged port as non-root, or SELinux restricts it.
Apache: AH00526: Syntax error on line 12 of /etc/apache2/sites-enabled/site.conf: Invalid command 'Foo', perhaps misspelled or defined by a module not included in the server configuration
Apache's config has a syntax problem or a directive from a module that isn't loaded.
Two steps away (35)
Error: Cannot find module 'x' (MODULE_NOT_FOUND)
Node can’t resolve the module path — the package isn’t installed, or a relative path/extension is wrong.
HTTP Error 500.30 - ASP.NET Core app failed to start
IIS/Azure’s ASP.NET Core Module launched your app but it crashed during startup.
java.lang.ExceptionInInitializerError
A static initializer (static block or static field) threw an exception while the class was loading.
Cannot connect to the Docker daemon at unix:///var/run/docker.sock. Is the docker daemon running?
The docker CLI can’t talk to the Docker engine — it isn’t running, or your user can’t access the socket.
Docker: Bind for 0.0.0.0:80 failed: port is already allocated
Another container or host process already publishes that host port.
HTTP 403 Forbidden
The server understood the request but refuses to authorize it — you (or the server process) are not allowed to access this resour…
Error: connect ECONNREFUSED 127.0.0.1:5432
Nothing is listening at that host:port — the target service is down or you’re connecting to the wrong address.
npm ERR! code ELIFECYCLE / Command failed with exit code 1
An npm script (build, start, test, postinstall) exited with an error. ELIFECYCLE is only the wrapper — the real error is printed…
Web server failed to start. Port 8080 was already in use.
Spring Boot couldn’t bind its embedded server port because another process uses it.
driver failed programming external connectivity on endpoint: iptables: No chain/target/match by that name
Docker’s iptables rules were wiped (firewalld/ufw reload, iptables flush) while Docker was running, so it can’t publish ports.
Nginx 444 No Response (connection closed without response)
An Nginx-specific code: the server deliberately closed the connection without sending anything — a rule is dropping the request.
Nginx 400: The SSL certificate error (495 / 496 client certificate)
Nginx rejected the request because the client certificate was invalid (495) or missing (496) on a site that requires mutual TLS.
HTTP 413 Content Too Large (Request Entity Too Large)
The request body is bigger than the server is willing to accept — usually a file upload over the configured limit.
OAuth Error: redirect_uri_mismatch
The redirect URI in your OAuth request doesn’t exactly match one registered for the client in the provider’s console.
WordPress: Error Establishing a Database Connection
WordPress can’t connect to its MySQL/MariaDB database with the credentials in wp-config.php, or the database server is down.
Job for nginx.service failed because the control process exited with error code
systemd tried to start the service, but its start command failed. The real reason is in the service’s status/journal.
Nginx: nginx: [emerg] unexpected end of file, expecting ";" or "}" in /etc/nginx/conf.d/site.conf:42
The config ends while a block or directive is still open — a missing `}` or `;`.
Browser: Welcome to nginx! If you see this page, the nginx web server is successfully installed and working
Requests are served by the default server block, not your site's block.
Apache: [authz_core:error] AH01630: client denied by server configuration: /var/www/html/
Apache 2.4 authorisation denied access to the directory (403) because no `Require all granted` applies.
Apache: [core:info] AH00128: File does not exist: /var/www/html/favicon.ico (404)
The requested file isn't in the DocumentRoot — a normal 404 entry in the Apache error log.
HTTP 500 Internal Server Error
The server hit an unexpected condition — usually an unhandled exception or misconfiguration in the application.
HTTP 499 Client Closed Request (Nginx)
Nginx-specific code logged when the client disconnected before the server finished responding.
Apache: AH02240: Server should be SSL-aware but has no certificate configured / SSLCertificateFile: file '/etc/ssl/x.crt' does not exist or is empty
Apache cannot find the certificate or key file named in its configuration, or `SSLEngine on` is set without any certificate.
FastCGI sent in stderr: "Primary script unknown"
Nginx passed a script path to PHP-FPM that PHP-FPM couldn’t find — usually a wrong SCRIPT_FILENAME or root.
WordPress: Your PHP installation appears to be missing the MySQL extension which is required by WordPress
PHP doesn’t have the mysqli extension loaded, so WordPress can’t talk to the database.
WordPress: Your server is running PHP version 7.2 but WordPress 6.x requires at least 7.4 / This plugin requires a newer version of PHP
WordPress core, a plugin or a theme needs a newer PHP than the server runs.
Failed to start x.service: Unit x.service not found
systemd has no unit with that name — the package isn’t installed, the name differs on this distro, or a new unit file wasn’t load…
System has not been booted with systemd as init system (PID 1). Can't operate.
You ran systemctl inside an environment without systemd as PID 1 — a Docker container or older WSL.
systemd: Start request repeated too quickly / service hit its start limit
The service crashed and restarted several times in a short period, so systemd stopped trying (StartLimitBurst).
user is not in the sudoers file. This incident will be reported.
Your account isn’t allowed to use sudo.
WordPress: Sorry, you are not allowed to access this page.
Your user role lacks the capability for that admin screen — or the database table prefix / user capabilities are out of sync afte…
Error: EPERM: operation not permitted, rename / unlink
The OS refused a file operation — on Windows usually because another process (antivirus, editor, indexer) has the file locked.
PHP Parse error: syntax error, unexpected …
PHP can’t parse the file because of a syntax mistake — the real error is often on the line before the one reported.
Apache: [ssl:warn] AH01909: example.com:443:0 server certificate does NOT include an ID which matches the server name
Apache's SSL virtual host name does not match any name inside the certificate it loads.
Nginx: nginx: [emerg] directive "proxy_pass" is not terminated by ";" in /etc/nginx/sites-enabled/app:15
A directive's arguments run into the next line because the `;` is missing (or a quote is unbalanced).
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