Guides tagged “troubleshooting”
Step-by-step MdmHost guides about troubleshooting, sorted A-Z.
178 guides · page 3 of 9
Fix "fork: Resource temporarily unavailable" on Linux
Fix Linux errors like fork: retry: Resource temporarily unavailable and Cannot allocate memory by checking process limits (nproc), systemd TasksMax, pid_max, runaway processes and memory.
Fix "HTTP error" and failed image uploads in WordPress
Fix WordPress media uploads that fail with "HTTP error", "exceeds the maximum upload size" or "unable to create directory": limits, permissions, image libraries and plugins.
Fix "Job for service failed" when a systemd service won't start
Diagnose systemd services that fail to start: read status and journal output, decode exit codes like 203/EXEC and 217/USER, test configs, and fix restart loops.
Fix "Maximum execution time exceeded" PHP errors
Fix the PHP fatal error 'Maximum execution time of 30 seconds exceeded': raise max_execution_time correctly, align web server timeouts and move long tasks out of web requests.
Fix "No space left on device" on Linux
Free disk space fast when Linux reports 'No space left on device': find what fills the disk, clear logs and caches safely, and fix inode exhaustion and deleted-but-open files.
Fix "No space left on device" when the disk isn't full (inodes)
Linux says no space left on device but df -h shows free space? Use df -i to confirm inode exhaustion, find the folder with millions of files and clean it up safely.
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.
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.
Fix "Remote Desktop can't connect to the remote computer"
Check the server is running, test the RDP port, rule out network blocks and repair Remote Desktop settings from the browser console.
Fix "Sorry, you are not allowed to access this page" in WordPress
Seeing "Sorry, you are not allowed to access this page" in wp-admin? Learn the causes, from lost admin roles and table prefix mismatches to plugins, and how to regain access.
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.
Fix "target is busy" and "Device or resource busy" on Linux
Unmount a disk that reports target is busy, find which processes hold files open with lsof and fuser, and handle busy files, swap and LVM devices safely.
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.
Fix "There has been a critical error on this website"
Recover from the WordPress critical error message: use the recovery mode email, find the failing plugin or theme in the logs and get back into the dashboard.
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.
Fix 403 Forbidden errors caused by ModSecurity (Imunify360 WAF)
Recognise when the Imunify360 web application firewall blocks a legitimate form or admin action with a 403 error, collect the details and get the rule fixed.
Fix 403 Forbidden errors on cPanel hosting
Solve 403 Forbidden on a cPanel website: missing index file, wrong permissions, .htaccess deny rules, IP Blocker entries, hotlink protection or ModSecurity blocks.
Fix 403 Forbidden in Nginx
Nginx returns 403 Forbidden when it will not serve a file or folder. Work through the usual causes, from a missing index file to permissions, deny rules and SELinux.
Fix 404 Not Found errors on cPanel hosting
Find why pages return 404 Not Found on a cPanel site: wrong document root, case-sensitive file names, missing rewrite rules, moved pages, and custom error pages.
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.
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