Linux Out of Memory (OOM): Find the Killer, Fix and Prevent Recurrence
Fix Linux out of memory: read OOM killer in dmesg/journalctl, use free and htop, systemd MemoryMax, swap as…
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systemd Service Failed to Start? Troubleshooting Guide for Linux
Fix systemd service failed to start: systemctl status, journalctl -u, ExecStart path and permissions, User=, dependencies, daemon-reload, and…
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Nginx 502 Bad Gateway: Causes and Fixes on Linux (Upstream, PHP-FPM, Timeouts)
Fix Nginx 502 Bad Gateway on Linux: check upstream is running, proxy_pass and fastcgi_pass, error.log messages, PHP-FPM pools,…
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ss Command on Linux: Listening Ports, Connections and Troubleshooting
Use ss on Linux instead of netstat: list listening TCP/UDP ports, show established connections, map sockets to PIDs,…
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chrony Not Syncing? Troubleshooting Time Sync on Linux
Fix chrony not syncing on Linux: read Not synchronised, 506 and 0 sources online errors, check the daemon,…
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Linux Performance Troubleshooting: top, iostat, vmstat Explained
Diagnose Linux performance problems with top, vmstat, and iostat: read load average, identify CPU vs I/O vs memory…
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Fix “Extension Not Found in Context” Dialplan Error in ViciDial/Asterisk
Fix the Asterisk error 'extension not found in context' (often seen on inbound trunks like trunkinbound) by locating…
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Fix “No One Is In Your Session” Error in ViciDial Agent Login
Fix the ViciDial agent login error 'no one is in your session' by checking SIP registration, stale phone…
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Fix “Sorry, Your Phone Login and Password Are Not Active” Error in ViciDial
Fix the ViciDial agent login error 'Sorry your phone login and password are not active in this System'…
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