u/Expensive-Rice-2052

Try: sudo ls -la /proc/1234/fd/

Info: Linux keeps deleted files on disk while any process has them open. /proc/PID/fd/ shows file descriptors with (deleted) marker for such files. Copy from there to recover.

Examples:

$ sudo lsof +L1 # Find all deleted-but-open files

$ sudo ls -la /proc/$(pgrep nginx)/fd/

$ sudo cp /proc/1234/fd/1 recovered.log

Note: Two steps: identify FD number, then copy. Works only while process runs. Restarting the process = data lost forever.

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covers RAID 0, 1, 5, 6, and 10, along with mdadm examples for creating arrays, checking status, simulating disk failures, replacing failed drives, monitoring rebuild progress, and growing an array. https://www.linuxteck.com/build-reliable-linux-storage-with-raid/

Try: watch -n 5 'ps -eo pid,user,vsz,rss,comm --sort=-rss | head -20'

Info: watch runs the command repeatedly showing memory trends. RSS shows physical memory in KB. If a process's RSS keeps growing, you have a leak.

Examples:

$ watch -n 1 'free -m'

$ smem -tk -s rss # More accurate memory reporting

$ sudo pmap -x 1234 | tail -1 # Detailed memory map

Note: smem is more accurate than ps for shared memory. Install: apt install smem. Monitor over hours to detect slow leaks.

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This is Part 4 of the Bash interview series. It focuses on the point where beginners move from running individual commands to writing actual scripts. https://www.linuxteck.com/write-your-first-bash-script/

It covers one-liners, file handling, regex, log processing, cron jobs, reports, arguments, and debugging with admin-focused examples. https://www.linuxteck.com/learn-perl-scripting-for-shell-users/

Try: sudo gdb -p 1234 -batch -ex 'thread apply all bt' -ex 'quit'

Info: gdb can attach to running processes and dump stack traces without stopping them. Essential for debugging production issues where you cannot restart the service.

Examples:

$ sudo gdb -p $(pgrep nginx) -batch -ex 'bt'

$ sudo strace -p 1234 -f -e trace=network

$ sudo perf record -p 1234 -g sleep 30

Note: gdb briefly pauses the process. For production, use 'perf' or 'strace' for less impact. Requires debug symbols for best results.

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Cloudways and Vultr based on real deployment work rather than feature lists alone : https://www.linuxteck.com/guides/cloudways-vs-vultr/

Try: sudo tcpdump -i eth0 -w capture.pcap 'host 192.168.1.100 and port 80 and tcp[13] & 2 != 0'

Info: tcpdump captures network packets with BPF filters. This example captures only SYN packets (TCP handshake start) to a specific host on port 80. Perfect for debugging network issues.

Examples:

$ sudo tcpdump -i any -n 'port 443 and host github.com'

$ sudo tcpdump -i eth0 -A 'tcp port 80' # Show ASCII payload

$ sudo tcpdump -r capture.pcap 'tcp[tcpflags] & (tcp-syn|tcp-ack) == tcp-syn'

Note: Use -w to save, -r to read pcap files. BPF filters: 'tcp[13] & 2' checks SYN flag. Open .pcap files in Wireshark for GUI analysis.

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Try: systemd-cgls --unit=docker.service

Info: systemd-cgls shows the cgroup tree with all processes organized by their control groups. Perfect for understanding container isolation and resource allocation.

Examples:

$ systemd-cgls --unit=user.slice

$ systemd-cgtop # Real-time cgroup resource usage

$ cat /proc/1234/cgroup # Show cgroups for specific PID

Note: Understand container resource isolation. Combine with 'systemd-cgtop' for real-time CPU/memory per cgroup. Essential for container troubleshooting.

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Try: sudo auditctl -w /etc/passwd -p wa -k passwd_changes

Info: auditd is Linux's audit framework. auditctl sets up a real-time watch on a file silently. You then use ausearch later to query those logs.

Examples:

$ sudo auditctl -w /etc/shadow -p rwxa -k shadow_access

$ sudo ausearch -k passwd_changes -ts today

$ sudo aureport --file --summary

Note: Requires auditd service. auditctl commands run silently and log events in the background. Use ausearch -k <key> later to inspect the generated logs when a file is changed.

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covers: https://www.linuxteck.com/linux-pam-architecture-explained/

• PAM Architecture
• Authentication flow
• PAM API and Library
• Configuration files
• Common PAM modules
• Practical use cases

covers: https://www.linuxteck.com/batch-command-in-linux/

• What batch does
• Syntax and examples
• Queue management
• batch vs at vs cron
• Practical use cases

Try: find /images -name '*.jpg' | parallel -j+0 'convert {} -resize 800x600 {}.resized'

Info: GNU parallel executes commands in parallel across all CPU cores. Dramatically speeds up batch processing of files, downloads, or any repeatable task.

Examples:

$ parallel -j 4 gzip ::: *.log

$ cat urls.txt | parallel -j 10 wget {}

$ find . -name '*.mp4' | parallel ffmpeg -i {} -vcodec h264 {.}.mp4

Note:Install: apt install parallel. -j+0 uses all cores, -j N uses N processes. ::: passes arguments directly. Perfect for CPU-intensive tasks.

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Try: lsof -p 3456

Info: lsof shows all files, sockets, and connections used by a process. Great for troubleshooting.

Examples:

$ lsof -p 3456

$ lsof -i :8080

$ lsof -u username

Note:Use -i for network connections. -i :PORT shows process using that port.

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including: https://www.linuxteck.com/cachyos-june-2026-release/

• Python Extended PGO
• GCC branch prediction tuning
• Pacman network isolation
• Hyprland Noctalia desktop
• DNS-over-QUIC support
• Multi-GPU driver conflict fixes
• Installer improvements and bug fixes

covering: https://www.linuxteck.com/linux-kernel-7-2-rc1-release/

• 43.8M+ lines of kernel code
• PCIe hot-plug speed regression fix
• Rust integration updates
• Security hardening improvements
• Removal of legacy drivers
• What Linux distributions can expect

Try:time ./backup.sh

Info:time command shows execution time. real=wall clock, user=CPU for program, sys=CPU for system calls.

Examples:

$ time ./deploy.sh

$ /usr/bin/time -v ./process.py

$ time tar -czf backup.tar.gz /home/data

Note:Use /usr/bin/time -v for detailed resource usage including memory.

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covers: https://www.linuxteck.com/ai-agents-for-devops-automation-guide/

• What AI agents are
• Infrastructure as Code (IaC)
• AI-assisted deployments
• Monitoring and automated remediation
• Benefits and current limitations
• Best practices for adoption

Try: rsync -avz --delete /source/ /destination/

Info: rsync only transfers changed files, making backups much faster. -a archive, -v verbose, -z compress.

Examples:

$ rsync -avz /home/user/ /mnt/backup/

$ rsync -avz --delete remote:/data/ /local/backup/

$ rsync -avz --exclude='*.tmp' /src/ /dst/

Note: Use --dry-run first. A trailing slash (/source/) copies contents; omitting it (/source) copies the folder itself.

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Includes: https://www.linuxteck.com/install-kali-linux-step-by-step/

• Downloading the correct Kali ISO
• VMware and physical installation
• Disk partitioning
• GRUB installation
• First login
• Post-installation verification
• Common installation tips