dmesg on Linux: Read Kernel Logs (Hardware, OOM, USB, Disk Errors)
Use dmesg on Linux for kernel ring buffer messages: dmesg -T timestamps, follow with -w, find OOM kills…
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tcpdump on Linux: Capture Packets by Port and Host (Filters & pcap)
Learn tcpdump on Linux: choose interface, capture to pcap, BPF filters for host and port, read files with…
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strace on Linux: Debug Slow Scripts and Permission Errors (Syscalls)
Use strace on Linux to see syscalls: trace open, connect, and read failures, attach to running PIDs, filter…
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ulimit on Linux: Fix “Too Many Open Files” (nofile, limits.conf, systemd)
Increase open file limits on Linux: ulimit -n, soft vs hard limits, /etc/security/limits.conf, systemd LimitNOFILE=, prlimit, and verify…
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Linux tail -f Command: Follow Log Files Live (nginx, apps, journalctl)
Use tail -f on Linux to follow log files in real time: -n line count, grep while tailing,…
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Linux free Command Explained: Memory, available, Swap and When RAM Is Full
Understand free -h on Linux: total, used, free, available, buffers/cache, swap, MemAvailable vs free column, and when to…
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Linux Load Average Explained: uptime, CPU Cores and When to Worry
Understand Linux load average from uptime and top: 1/5/15 minute values, compare to CPU core count, iowait vs…
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Docker logs and docker exec: Debug Containers on Linux (Compose Included)
Debug Docker on Linux: docker logs --tail and -f, docker ps -a exit codes, docker exec into containers,…
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Reset Root Password on Linux: GRUB Single-User Mode and Recovery (Ubuntu/RHEL)
Reset forgotten Linux root password: GRUB boot menu, edit linux line init=/bin/bash, remount rw, passwd root, cloud VPS…
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SSH Connection Refused on Linux: Fix Port, sshd, Firewall and SELinux
Fix SSH connection refused: verify sshd is running and listening, correct Port in sshd_config, UFW/firewalld and cloud security…
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