# Troubleshooting Source: https://vpsdime.com/knowledgebase/troubleshooting Last reviewed: 2026-07-02 Summary: Fixes for the most common VPS problems, restoring SSH access, firewall lockouts, the host identification changed warning, DNS resolution failures inside the VPS, cPanel login blocks, changing the SSH port, and understanding memory usage. Fixes for the problems that generate the most tickets, most are self-service in minutes. If your VPS is unreachable and you want a guided diagnosis, start with [My VPS is Down](https://vpsdime.com/knowledgebase/client-area/support/vps-troubleshooter), it checks your VPS and fixes several causes on the spot. ## Start here - [How to troubleshoot anything (and where everything logs)](https://vpsdime.com/knowledgebase/troubleshooting/troubleshooting-method). The method, the question-to-command table, and the log atlas every guide below assumes. ## Can't get in - [My IP is blocked. How do I unblock it?](https://vpsdime.com/knowledgebase/troubleshooting/ip-blocked) The four layers that can block an IP, how to tell which one got you, the fastest unblock for each, and prevention. - [How to restore my SSH access](https://vpsdime.com/knowledgebase/troubleshooting/restore-ssh-access). The step-by-step diagnosis: banned IP, your own firewall, or SSH itself. - [Commands to allow SSH access in common firewalls](https://vpsdime.com/knowledgebase/troubleshooting/allow-ssh-in-common-firewalls). The exact commands for ufw, CSF, firewalld, iptables, and nft. - [WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED](https://vpsdime.com/knowledgebase/troubleshooting/host-identification-changed). Normal after a reinstall, here's the one-line fix. - [cPanel/WHM: root login suddenly fails (cPHulk)](https://vpsdime.com/knowledgebase/troubleshooting/cpanel-cphulk-login-blocked). cPanel's brute-force protection locking you out of your own server. ## Network - [Understanding and troubleshooting network problems](https://vpsdime.com/knowledgebase/troubleshooting/network-problems). Whose fault is the lag, yours, ours, or a carrier in between, and how to prove it with mtr. - [Testing your VPS network speed](https://vpsdime.com/knowledgebase/troubleshooting/testing-network-speed). Speedtest CLI, our per-location test files, iperf3, and reading single- vs multi-stream results. - [My Port XXX is closed. Can you open it?](https://vpsdime.com/knowledgebase/troubleshooting/my-port-xxx-is-closed) Nothing to open, ports show open only when something listens, plus closed vs filtered decoded. - [Bots and crawlers are hammering my website](https://vpsdime.com/knowledgebase/troubleshooting/bot-traffic). Identify them in the access log, robots.txt vs rate limiting vs fail2ban vs Cloudflare. ## Email - [Emails from my VPS go to spam](https://vpsdime.com/knowledgebase/troubleshooting/emails-going-to-spam). Diagnose with mail-tester and MXToolbox, then rDNS, SPF, DKIM, DMARC, and reputation. - [My mail server isn't receiving email](https://vpsdime.com/knowledgebase/troubleshooting/cannot-receive-email). The inbound chain: MX record, port 25 listener, outside testing, and the mail log. ## Inside the VPS - [My VPS is slow. How do I find out why?](https://vpsdime.com/knowledgebase/troubleshooting/slow-vps) The systematic walk-through: path vs server, OOM kills, the four CPU hogs, monitoring, and website tuning. - [Fixing 502, 503, and 504 errors](https://vpsdime.com/knowledgebase/troubleshooting/502-503-errors). The web server answered, the app behind it didn't, decode the error, read the proxy log, and the Docker cases. - [Fixing SSL certificate errors](https://vpsdime.com/knowledgebase/troubleshooting/ssl-certificate-errors). Expired (the day-91 renewal failure), name mismatches, chains, mixed content, and Cloudflare's SSL modes. - [Fixing 403 Forbidden errors](https://vpsdime.com/knowledgebase/troubleshooting/403-forbidden). Ownership after uploads, missing index files, deny rules, and why never chmod 777. - [My website didn't come back after a reboot or unsuspension](https://vpsdime.com/knowledgebase/troubleshooting/services-not-starting-after-reboot). Started is not enabled, the fix for the post-payment "VPS is up but site is down". - [My VPS was hacked. Recovery, step by step](https://vpsdime.com/knowledgebase/troubleshooting/compromised-vps-recovery). Why modern bots survive cleanup, the backup-and-reinstall routine, and how our suspension process works. - [Chrome shows a "Dangerous site" warning on my website](https://vpsdime.com/knowledgebase/troubleshooting/chrome-dangerous-site-warning). Google Safe Browsing flags, what was flagged, the cleanup, and the review that lifts it. - [I deleted files by accident. Can they be recovered?](https://vpsdime.com/knowledgebase/troubleshooting/recover-deleted-files) Stop writes, honest odds, and the real recovery paths through backups. - [MySQL or MariaDB won't start after a crash](https://vpsdime.com/knowledgebase/troubleshooting/mysql-wont-start). The safe order: logs, disk, OOM, patient recovery, and force_recovery only to dump and rebuild. - [My cron job didn't run](https://vpsdime.com/knowledgebase/troubleshooting/cron-not-running). The empty PATH, the % gotcha, silent failures, and making them noisy. - [Error: Failed to detect code in SYSLOG log (lfd)](https://vpsdime.com/knowledgebase/troubleshooting/lfd-failed-to-detect-code). The rsyslog imjournal bug behind the alert, and the two fixes. - [Temporary failure resolving (DNS errors during updates)](https://vpsdime.com/knowledgebase/troubleshooting/temporary-failure-resolving). The systemd-resolved fix. - [My disk is full (and it took my website or database down)](https://vpsdime.com/knowledgebase/troubleshooting/disk-full). The hidden cause behind "my site is offline" and "MySQL won't start", find it, clean it safely, prevent it. - [No space left on device, but df shows free space](https://vpsdime.com/knowledgebase/troubleshooting/out-of-inodes). The often-missed inode exhaustion: millions of tiny files, not big ones. - [My VPS is using too much memory. What's wrong?](https://vpsdime.com/knowledgebase/troubleshooting/vps-using-too-much-memory). It probably isn't, how Linux memory really works. - [Why can't I clear the RAM cache?](https://vpsdime.com/knowledgebase/troubleshooting/clear-ram-cache). You don't need to, and here's why. --- Still need a person? You can [open a support ticket](https://vpsdime.com/open-ticket/) any time.