OhSudo — new Networking articlesNew Networking articles from OhSudo: practical fixes for DevOps engineers, SysAdmins and IT folks.https://ohsudo.com/en-usNginx "upstream sent too big header while reading response header": raise the right bufferhttps://ohsudo.com/articles/nginx-upstream-sent-too-big-header/https://ohsudo.com/articles/nginx-upstream-sent-too-big-header/Fix Nginx "upstream sent too big header while reading response header from upstream" and its 502: measure the headers, then raise the right buffer.Sat, 14 Nov 2026 00:00:00 GMTNetworkingnginxreverse-proxyphp-fpmbuffers502troubleshootingcontact@ohsudo.com (OhSudo)"No route to host": usually a firewall saying no, sometimes a machine that isn't therehttps://ohsudo.com/articles/no-route-to-host/https://ohsudo.com/articles/no-route-to-host/Fix "No route to host" from ssh, curl or nc: check the firewall on the other machine (firewalld rejects by default), then whether the host is up.Thu, 12 Nov 2026 00:00:00 GMTNetworkingnetworkingfirewalldsshroutingrheltroubleshootingcontact@ohsudo.com (OhSudo)"Blocked by CORS policy": what the browser is really refusing, and how to fix it on the serverhttps://ohsudo.com/articles/blocked-by-cors-policy/https://ohsudo.com/articles/blocked-by-cors-policy/Fix "has been blocked by CORS policy: No Access-Control-Allow-Origin header": why it happens, the fix on the server or in Nginx, preflight requests, and cookies.Sat, 07 Nov 2026 00:00:00 GMTNetworkingcorsnginxhttp-headersapibrowsertroubleshootingcontact@ohsudo.com (OhSudo)Nginx "403 Forbidden": read the error log, then fix the index, permissions or SELinuxhttps://ohsudo.com/articles/nginx-403-forbidden/https://ohsudo.com/articles/nginx-403-forbidden/Fix Nginx "403 Forbidden": the error log says if it's a missing index file, wrong permissions on a parent folder, a deny rule or SELinux. namei checks the whole path.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxpermissionsselinuxnameiweb-servertroubleshootingcontact@ohsudo.com (OhSudo)Nginx for Laravel with PHP-FPM: production config, permissions and queueshttps://ohsudo.com/articles/nginx-laravel-php-fpm/https://ohsudo.com/articles/nginx-laravel-php-fpm/Deploy Laravel on Nginx and PHP-FPM: a complete HTTPS config pointing at public, permissions for storage, the optimize and queue steps, and the errors you may see.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxlaravelphp-fpmphpdeploymentnginx-guidecontact@ohsudo.com (OhSudo)Nginx for a React or Vite single-page app: routes, caching and an API proxyhttps://ohsudo.com/articles/nginx-react-vite-single-page-app/https://ohsudo.com/articles/nginx-react-vite-single-page-app/Serve a React, Vue or Vite single-page app with Nginx: fix 404s on refresh with try_files, cache hashed assets, avoid caching index.html, and proxy /api to your backend.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxreactvitespacachingnginx-guidecontact@ohsudo.com (OhSudo)Nginx and Gunicorn for Django: production config, static files and HTTPShttps://ohsudo.com/articles/nginx-reverse-proxy-django-gunicorn/https://ohsudo.com/articles/nginx-reverse-proxy-django-gunicorn/Deploy Django with Gunicorn behind Nginx: a complete HTTPS config, a socket with systemd, static and media files, the settings you need behind a proxy, and common errors.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxdjangogunicornpythonstatic-filesnginx-guidecontact@ohsudo.com (OhSudo)Nginx reverse proxy with Docker Compose: in a container or on the hosthttps://ohsudo.com/articles/nginx-reverse-proxy-docker-compose/https://ohsudo.com/articles/nginx-reverse-proxy-docker-compose/Put Nginx in front of Docker Compose services: on the host or in a container, connect by service name, fix "host not found in upstream", keep ports private, add HTTPS.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxdockerdocker-composereverse-proxycontainersnginx-guidecontact@ohsudo.com (OhSudo)Nginx reverse proxy for FastAPI and Uvicorn, with HTTPS and WebSocketshttps://ohsudo.com/articles/nginx-reverse-proxy-fastapi-uvicorn/https://ohsudo.com/articles/nginx-reverse-proxy-fastapi-uvicorn/Run FastAPI behind Nginx: a complete HTTPS config, Uvicorn in a systemd service, proxy headers for the real client IP, a subpath, WebSockets, and common errors.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxfastapiuvicornpythonreverse-proxynginx-guidecontact@ohsudo.com (OhSudo)Nginx reverse proxy for Ghost: HTTPS, the url setting and redirect loopshttps://ohsudo.com/articles/nginx-reverse-proxy-ghost/https://ohsudo.com/articles/nginx-reverse-proxy-ghost/Put Nginx in front of a Ghost blog: a complete HTTPS config, the url setting, X-Forwarded-Proto to avoid redirect loops, upload limits, Docker Compose, and common errors.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxghostnodejsreverse-proxyblognginx-guidecontact@ohsudo.com (OhSudo)Nginx for Next.js: a production config with HTTPS, caching and standalone buildshttps://ohsudo.com/articles/nginx-reverse-proxy-nextjs/https://ohsudo.com/articles/nginx-reverse-proxy-nextjs/Run Next.js behind Nginx: a complete config with HTTPS and long caching for _next/static, the standalone build, a systemd service, and the errors people run into.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxnextjsreactreverse-proxycachingnginx-guidecontact@ohsudo.com (OhSudo)Nginx reverse proxy for Node.js and Express, with HTTPS and WebSocketshttps://ohsudo.com/articles/nginx-reverse-proxy-nodejs-express/https://ohsudo.com/articles/nginx-reverse-proxy-nodejs-express/Set up Nginx in front of a Node.js or Express app: a complete config with HTTPS and WebSockets, a systemd service, trust proxy for real client IPs, and common errors.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxnodejsexpressreverse-proxywebsocketsnginx-guidecontact@ohsudo.com (OhSudo)Nginx for WordPress with PHP-FPM: a complete, safe confighttps://ohsudo.com/articles/nginx-wordpress-php-fpm/https://ohsudo.com/articles/nginx-wordpress-php-fpm/Run WordPress on Nginx and PHP-FPM: a complete HTTPS config, pretty permalinks, blocking PHP in uploads, upload limits, caching and the common errors, step by step.Fri, 06 Nov 2026 00:00:00 GMTNetworkingnginxwordpressphp-fpmphpsecuritynginx-guidecontact@ohsudo.com (OhSudo)Apache "AH00558: Could not reliably determine the server's fully qualified domain name": what it means, and the fixhttps://ohsudo.com/articles/apache-ah00558-could-not-reliably-determine-fqdn/https://ohsudo.com/articles/apache-ah00558-could-not-reliably-determine-fqdn/Fix Apache AH00558: it's only a warning, set ServerName globally on Ubuntu or RHEL. If your site is still down, the real error is elsewhere, and here is how to find it.Thu, 05 Nov 2026 00:00:00 GMTNetworkingapachehttpdubuntusystemdweb-serverstroubleshootingcontact@ohsudo.com (OhSudo)ERR_TOO_MANY_REDIRECTS with Nginx and Cloudflare: find the loop and break ithttps://ohsudo.com/articles/err-too-many-redirects-nginx-cloudflare/https://ohsudo.com/articles/err-too-many-redirects-nginx-cloudflare/Fix ERR_TOO_MANY_REDIRECTS: follow the loop with curl, then fix Cloudflare Flexible SSL, HTTPS redirects behind a proxy, X-Forwarded-Proto and www redirects that fight.Thu, 05 Nov 2026 00:00:00 GMTNetworkingnginxcloudflarehttpsredirectsproxytroubleshootingcontact@ohsudo.com (OhSudo)Nginx "504 Gateway Time-out": find out what's slow before raising the timeouthttps://ohsudo.com/articles/nginx-504-gateway-time-out/https://ohsudo.com/articles/nginx-504-gateway-time-out/Fix Nginx "504 Gateway Time-out": read the error log, measure the backend, set proxy_read_timeout or fastcgi_read_timeout, and check Cloudflare and load balancers.Thu, 05 Nov 2026 00:00:00 GMTNetworkingnginxreverse-proxyphp-fpmtimeoutscloudflaretroubleshootingcontact@ohsudo.com (OhSudo)"Connection timed out" vs "Connection refused": what each one tells you, and how to fix ithttps://ohsudo.com/articles/connection-timed-out-vs-connection-refused/https://ohsudo.com/articles/connection-timed-out-vs-connection-refused/Timed out means a firewall dropped the packets; refused means nothing listens there. Tell them apart with nc and curl, then fix ufw, firewalld or the bind address.Wed, 04 Nov 2026 00:00:00 GMTNetworkingnetworkingfirewallufwfirewalldsscurlnctroubleshootingcontact@ohsudo.com (OhSudo)Nginx "413 Request Entity Too Large": raise the upload limit in the right placehttps://ohsudo.com/articles/nginx-413-request-entity-too-large/https://ohsudo.com/articles/nginx-413-request-entity-too-large/Fix 413 Request Entity Too Large on uploads: set client_max_body_size in nginx, then the limits of PHP, Node.js, the Kubernetes ingress and any proxy in front.Mon, 02 Nov 2026 00:00:00 GMTNetworkingnginxuploadsphpnodejskubernetesingresstroubleshootingcontact@ohsudo.com (OhSudo)"Temporary failure in name resolution": fix DNS on a Linux serverhttps://ohsudo.com/articles/temporary-failure-in-name-resolution/https://ohsudo.com/articles/temporary-failure-in-name-resolution/Fix "Temporary failure in name resolution" and "Could not resolve host" on Linux: tell DNS from network problems, check systemd-resolved, and set DNS servers that stick.Mon, 02 Nov 2026 00:00:00 GMTNetworkingdnssystemd-resolvednetplannetworkmanagerdockertroubleshootingcontact@ohsudo.com (OhSudo)"Address already in use": find who is using port 80 (or any port)https://ohsudo.com/articles/address-already-in-use-port-80/https://ohsudo.com/articles/address-already-in-use-port-80/Fix "bind() failed (98: Address already in use)": find the process holding the port with ss or lsof, then stop it, move it, or change your port.Sun, 01 Nov 2026 00:00:00 GMTNetworkingportsnginxapachesslsofsystemdtroubleshootingcontact@ohsudo.com (OhSudo)Nginx "502 Bad Gateway": find the cause in the error loghttps://ohsudo.com/articles/nginx-502-bad-gateway/https://ohsudo.com/articles/nginx-502-bad-gateway/Fix nginx 502 Bad Gateway: read error.log, then fix the backend that is down, the wrong address or socket, the crashing app, or SELinux on RHEL.Sun, 01 Nov 2026 00:00:00 GMTNetworkingnginxreverse-proxy502systemdselinuxtroubleshootingcontact@ohsudo.com (OhSudo)