Find useful Linux logs with journalctl
Filter the system journal by boot, service, time, and priority, then preserve a small useful excerpt for troubleshooting.
Read guide →GLWS · KNOWLEDGE BASE
Troubleshooting.
Find the cause before you change anything.
Diagnose problems on a Linux VPS: slowness, full disks, Nginx 502 and 504 errors, packet loss, HTTPS renewal failures and getting back in after a lockout.
When something breaks, the fastest route is evidence: logs, resource figures and the exact error message. These guides show where to look and how to read what you find.
Each one ends with what to collect if you need to contact support.
10 troubleshooting guides
Get back into a server you have locked yourself out of
Use your provider's console to repair SSH settings, a firewall mistake or a lost password, with a boot-menu fallback for a forgotten account password.
Read guide →Why is my VPS slow? CPU steal, memory, swap and disk
Tell CPU steal, memory pressure, swapping and slow disk apart with a few commands, then collect evidence before you ask support or upgrade.
Read guide →Fix "No space left on device" on Linux
Tell a full disk from exhausted inodes, find what is using the space, clean up logs, packages and Docker data safely and stop it returning.
Read guide →Troubleshoot Nginx 502 and 504 errors
Follow a request from Nginx to your application, read the error log, check ports, services, SELinux and timeouts and fix the common causes.
Read guide →Diagnose packet loss and slow downloads
Measure latency, loss and throughput with ping, mtr and iperf3, read the results correctly and gather useful evidence for a support ticket.
Read guide →Troubleshoot HTTPS certificate renewal failures
Find why Let's Encrypt renewal fails: check the timer, DNS and AAAA records, port 80, redirects, reverse proxy rules and rate limits.
Read guide →Fix Cloudflare errors 521, 522, 525 and 526
Tell origin-down, timeout and TLS errors apart, test your origin directly, open the firewall for Cloudflare and fix certificates and SSL mode.
Read guide →Why was my Linux process "Killed"? Diagnose out-of-memory failures
Confirm an out-of-memory kill in the kernel log, find what used the memory, and fix it with limits, swap, tuning or a bigger plan.
Read guide →Troubleshoot SSH "Permission denied" errors
Read the verbose output, then check the user name, key offered, file permissions, server settings and logs to fix publickey and password failures.
Read guide →Other topics
Getting started · Linux basics · System administration · Security · Server administration · Kubernetes · Monitoring · Networking · Web hosting · Data and storage · AI and LLMs · Self-hosting
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