The kernel is using tons of RAM. Which modules are the biggest? Try: sudo lsmod | sort -k2 -rn | head -10 Info: lsmod lists currently loaded kernel modules alongside their size in bytes. Sorting numerically by size quickly highlights memory-intensive display drivers, filesystems, and device modules. Examples: $ sudo […]
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My server clocks drift. How do I get millisecond-accurate time sync? Try: chronyc tracking Info: chrony replaces legacy ntpd with faster clock convergence and better accuracy on VM/cloud instances. Running chronyc tracking monitors stratum, offset, and real-time sync performance. Examples: $ sudo chronyc sourcestats # View drill-down statistics for active […]
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My server is swapping. Which processes are the culprits? Try: for pid in $(ls /proc/ | grep -E '^[0-9]+$'); do awk -v pid=$pid '/VmSwap/ {print pid, $2, $3}' /proc/$pid/status 2>/dev/null; done | sort -k2 -rn | head -10 Info: /proc/PID/status tracks per-process VmSwap usage. Iterating through numeric PIDs extracts and […]
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Some files won't delete due to attributes. How do I find Linux file attributes? Try: sudo lsattr -R /var/log 2>/dev/null | grep -E '^-*[aiu]' | head -10 Info: Linux file attributes control how files can be modified or deleted. The i attribute makes a file immutable, a enables append-only access, […]
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How do I count error occurrences in Linux over time? Try: watch -n 5 'grep -c "ERROR" /var/log/nginx/error.log' Info: watch reruns commands at defined intervals (-n seconds) to track changing metrics. Coupling tail -f with awk increments and displays a live rolling tally as new log entries land. Examples: $ […]
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Which system calls is a slow process making the most? Try: sudo perf trace -p 3456 --summary Info: perf trace offers lower overhead than strace. Using --summary aggregates syscall frequency and latency metrics (min/avg/max/stddev) to reveal true application execution bottlenecks. Examples: $ sudo perf trace -p 3456 # Trace live […]
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How do I create an encrypted compressed backup in Linux? Try: tar -czf - /home/linuxteck/documents | openssl enc -aes-256-cbc -pbkdf2 -out backup.tar.gz.enc Info: tar -czf - writes the compressed archive directly to standard output. Piping it to openssl enc encrypts the archive on the fly, so the unencrypted backup does […]
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After copying files, timestamps changed. How do I preserve them? Try: rsync -a --preserve-times /source/ /destination/ Info: rsync -a (archive mode) preserves modification timestamps (-t), permissions, ownership, and symbolic links. Adding --preserve-times explicitly ensures file modification times remain unchanged during the transfer. Examples: $ cp --preserve=timestamps file1 file2 # Preserve […]
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My server hits "too many open files" errors. Which process is the culprit? Try: sudo lsof | awk '{print $2}' | sort | uniq -c | sort -rn | head -10 Info: lsof lists open file descriptors across processes. Grouping the output by PID counts open handles and helps identify […]
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My server ran out of disk. Which files grew the most in the last 24 hours? Try: sudo find / -type f -mtime -1 -size +100M -exec ls -lah {} \; 2>/dev/null Info: Uses -mtime -1 to target files modified within the last 24 hours and -size +100M to isolate […]
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How do I set 644 for files and 755 for directories in one shot? Try: find /var/www/site -type d -exec chmod 755 {} + && find /var/www/site -type f -exec chmod 644 {} + Info: Uses -type d to grant directories execute permissions (755) and -type f to grant files […]
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Which network interface is being overloaded? Try: sar -n DEV 1 5 Info: sar -n DEV displays real-time network interface statistics. The 1 5 arguments sample network activity every 1 second for 5 samples, showing throughput such as rxkB/s and txkB/s, along with packet rates. Examples: $ sar -n TCP […]
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How do I see all differences between production and my feature branch? Try: git log --oneline --left-right --graph main...feature/new-api Info: The three-dot ... notation compares the two branches from their common ancestor. --left-right marks commits unique to the left branch with < and commits unique to the right branch with […]
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I need SSL for local development. How do I generate a certificate quickly? Try: openssl req -x509 -newkey rsa:4096 -keyout key.pem -out cert.pem -sha256 -days 365 -nodes -subj '/CN=localhost' Info: Generates a 4096-bit RSA self-signed certificate valid for 1 year. The -x509 option creates a self-signed certificate, while -subj supplies […]
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My high-priority process needs dedicated cores. How do I pin it to specific CPUs? Try: taskset -cp 0,1 3456 Info: taskset sets or retrieves CPU affinity. The -c option specifies CPU numbers, while -p applies the affinity to an existing process by PID. Examples: $ taskset -c 0-3 ./program # […]
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My logs are eating disk space. How do I compress old ones and keep only 30 days? Try: find /var/log/app -name '*.log' -mtime +7 -exec gzip {} \; && find /var/log/app -name '*.log.gz' -mtime +30 -delete Info: Compresses logs older than 7 days with gzip to save disk space, then […]
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