Posts
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SSH Agent Forwarding: How It Works
Understand SSH agent forwarding security risks. When it's safe (almost never), and better alternatives like ProxyJump for jump hosts.
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Is Your Linux Server Destroying Its SSD?
Default mount options and journald settings burn SSD write endurance. Check health with smartctl, mount noatime, move logs to tmpfs, find the real writer.
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Docker Compose Profiles: Run Only What You Need
Profiles let you conditionally start services in Compose. Perfect for dev vs prod service splits without multiple files.
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journalctl Queries Every Sysadmin Needs
Essential journalctl commands: -u, -f, --since, -p, -k, -b, --no-pager, JSON output. The queries you need on a broken server at 2 AM.
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Why Your SSH Connection Keeps Dropping
Fix SSH timeouts: ServerAliveInterval, ServerAliveCountMax, ClientAliveInterval. Understand NAT, firewalls, and TCP keepalive.
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ss Is the New netstat (And It's Better)
ss replaces netstat on modern Linux: faster, shows more socket detail, and reads from the kernel. Every netstat command you rely on, rewritten for ss.
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Cleaning Up Docker Disk Space the Right Way
docker system prune reclaims space and can delete volumes you wanted. What each cleanup command removes, how to check usage first, and a safe script.
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Why Your Cron Job Is Failing Silently
Cron runs a different PATH, mutes stdout, and breaks MAILTO quietly. Absolute paths, an explicit PATH, log redirection, and how to test a job first.
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SSH Multiplexing: Stop Reconnecting Every Time
Master SSH ControlMaster, ControlPath, and ControlPersist. Reuse connections for lightning-fast SSH, SCP, and rsync operations.
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The Linux OOM Killer: Why It's Killing Your App
Why Linux kills your app with no warning. Understand the OOM killer, read dmesg logs, and shield critical processes with oom_score_adj and swap.
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Stop Putting Passwords in Docker ENV
ENV bakes secrets into image layers that docker history shows to anyone. Use BuildKit secret mounts, runtime variables, or a real secrets manager.
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find Flags You Keep Forgetting
Practical find command examples: -mtime, -newer, -type, -exec vs xargs, -not, size filters. The patterns you google every time.
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