Step-by-step help for your hosting

• Fix "SSL certificate problem: unable to get local issuer certificate"

  Fix TLS verification errors when your server, PHP, curl, Node.js or Python calls HTTPS APIs: outdated CA bundles, missing intermediate certificates, wrong clock and proxies.

  IntermediateLinux VPS3 min read

• Flush DNS cache on Windows, macOS, Linux and browsers

  Clear cached DNS answers after changing records or moving hosts: commands for Windows, macOS, Linux (systemd-resolved, nscd, dnsmasq), Chrome and Firefox, and when flushing won't help.

  BeginnerEveryone2 min read

• Fix MySQL "Too many connections" (error 1040)

  Find out why MySQL or MariaDB runs out of connections, see who holds them, fix slow queries and connection leaks, and size max_connections safely for your RAM.

  IntermediateLinux VPS3 min read

• Fix "Temporary failure in name resolution" on Linux

  Fix DNS lookups failing on a Linux server: check resolv.conf and systemd-resolved, set working nameservers, test with dig, and rule out firewall and network problems.

  IntermediateLinux VPS3 min read

• Fix "Cannot modify header information - headers already sent"

  Fix the PHP warning 'headers already sent by output started at file:line': stray whitespace, BOM characters, echo before redirects, closing tags and plugin output.

  BeginnercPanel hosting · Linux VPS3 min read

• Fix 500 Internal Server Error for PHP sites on a VPS

  Track down a PHP 500 Internal Server Error on your own Nginx or Apache server: read the right logs, then fix fatal errors, permissions, .htaccess, FPM and SELinux causes.

  IntermediateLinux VPS3 min read

• Fix common Composer errors on a server

  Solve frequent Composer problems: memory exhausted, PHP version or extension requirements, dependency conflicts, lock file mismatches, authentication and running as root.

  IntermediatecPanel hosting · Linux VPS3 min read

• Fix "command not found" errors on Linux

  Find out why bash says command not found: package not installed, wrong PATH, typos, sudo's secure_path, version-specific binaries and scripts with Windows line endings.

  BeginnerLinux VPS3 min read

• Fix 503 errors for Node.js apps in cPanel (Setup Node.js App)

  Diagnose 503 Service Unavailable and startup failures for apps created in cPanel's Setup Node.js App: startup file, dependencies, ports, logs and CloudLinux resource limits.

  IntermediatecPanel hosting3 min read

• Fix out-of-memory kills: the Linux OOM killer explained

  Recognise when the Linux OOM killer stopped MySQL, PHP or Node.js, find which process used the memory, and prevent it with right-sized limits, swap and service settings.

  IntermediateLinux VPS3 min read

• KVM and libvirt common errors and how to fix them

  Fix the most common KVM and libvirt errors: /dev/kvm missing, permission denied on images, network default not active, domain already exists, failed to connect to the hypervisor and more.

  IntermediateKVM hosts2 min read

• Debug a blank white page in PHP (display and log errors)

  Turn a blank PHP page into a readable error: enable error logging safely, find the right log file on cPanel or a VPS, and fix the usual causes like syntax errors and missing extensions.

  BeginnercPanel hosting · Linux VPS3 min read

• Fix "Permission denied" errors on Linux

  Work out why Linux says Permission denied: missing execute bits, directory permissions, wrong owner, sudo needed, noexec mounts, SELinux or AppArmor, with a fix for each.

  BeginnerLinux VPS3 min read

• SMTP reply codes explained: 2xx, 4xx and 5xx email errors

  How to read SMTP reply codes and enhanced status codes in bounces and logs, what common 421, 450, 550, 552 and 554 errors mean, and what to do about each one.

  IntermediateEmail3 min read

• How to read email headers and trace a message's path

  View full email headers in common mail apps and read Received lines, Authentication-Results, SPF, DKIM and DMARC verdicts, spam scores and delays to diagnose delivery problems.

  IntermediateEmail3 min read

• Fix a Virtualizor slave server that shows offline

  Troubleshoot Virtualizor master-to-slave connection problems: check network and ports, the slave service, API key, licence status, disk space and recent firewall changes.

  AdvancedVirtualizor admin2 min read

• Fix "Too many open files" errors on Linux

  Understand file descriptor limits, check what a process is allowed and using, and raise limits correctly for systemd services, Nginx, MySQL, Node.js and user sessions.

  IntermediateLinux VPS3 min read

• Fix "Read-only file system" errors on a Linux VPS

  Find out why Linux remounted a disk read-only, check kernel logs for disk or filesystem errors, run fsck safely from rescue mode and recover writes without losing data.

  AdvancedLinux VPS3 min read

• Repair an unbootable Linux VPS from rescue mode with chroot

  Boot a broken VPS into a rescue system, find and mount its disk, chroot into it, then fix common problems: bad fstab, broken GRUB, lost SSH access, full disk or a failed kernel update.

  AdvancedLinux VPS2 min read

• Fix Virtualizor WHMCS provisioning errors

  Troubleshoot the Virtualizor WHMCS module when orders fail: read the module log, fix API credentials, plan and server group mapping, IP pool shortages and OS template IDs.

  AdvancedWHMCS2 min read

Browse by topic

• Getting startedYour first hour with a new server: access, logins and basics.83 guides
• cPanelFiles, databases, email, domains and every cPanel tool, step by step.67 guides
• WHM & resellingWHM, packages, reseller accounts, WHMReseller and running a hosting brand.53 guides
• WordPressInstall, secure, speed up, migrate and fix WordPress sites.49 guides
• Email & webmailMailboxes, webmail, forwarders, spam filters and email delivery.67 guides
• DomainsRegistering, transferring and managing domains and nameservers.27 guides
• SSL certificatesFree AutoSSL, Let's Encrypt, paid certificates and HTTPS.41 guides
• CloudLinuxCloudLinux setup and use: LVE limits, CloudLinux Manager, CageFS and PHP/Node.js selectors.31 guides
• LiteSpeedLiteSpeed Web Server, LSCache and the LiteSpeed Cache plugin: install, settings and tuning.35 guides
• Imunify360Malware scanning, firewall and proactive defence with Imunify360.24 guides
• SoftaculousInstall, update, clone and back up apps with Softaculous.24 guides
• WP SquaredcPanel's WordPress platform: sites, plugins, staging and backups.9 guides
• SitePadBuild and publish websites with the SitePad builder.9 guides
• SitejetDesign, edit and publish sites with the Sitejet builder.9 guides
• WHMResellerAlpha and master resellers with WHMReseller: install, setup and use.12 guides
• VirtFusionInstall, set up and manage VirtFusion: hypervisors, packages, servers and WHMCS integration.28 guides
• VirtualizorManage your VPS with Virtualizor: power, OS reinstall, VNC, IPs and backups.44 guides
• PleskWebsites, email, databases and settings in the Plesk panel.53 guides
• DirectAdminUsers, domains, email and reseller tools in DirectAdmin.41 guides
• WHMCSBilling, automation, products and client management with WHMCS.52 guides
• Control panelscPanel & WHM, Plesk, DirectAdmin and other panels on your VPS.107 guides
• SecurityKeys, passwords, firewalls and keeping a server patched.138 guides
• Networking & DNSIP addresses, reverse DNS, ports and traffic.72 guides
• Websites & appsWeb servers, WordPress, PHP, Node.js, SSL and app hosting.83 guides
• DatabasesMySQL, MariaDB, PostgreSQL, Redis and MongoDB on a VPS.80 guides
• Billing & accountInvoices, renewals, the client area and your account.9 guides
• TroubleshootingWhen something is not working: checks and fixes.127 guides
• Linux VPSSSH, packages, services and everyday Linux administration.265 guides
• Windows VPS & RDPRemote Desktop, Windows Server settings and Admin RDP tips.73 guides
• Docker & DevOpsContainers, Git deploys, automation, monitoring and backups.82 guides