Posts
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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 is useful but risky. Learn what each cleanup command does and how to check disk usage safely.
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Why Your Cron Job Is Failing Silently
PATH is different in cron, stdout is muted, and MAILTO breaks silently. Learn cron traps and how to debug them.
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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 layers visible in docker history. Use BuildKit --secret, runtime vars, or .env files.
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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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The SSH Config File: The Shortcut You're Not Using
Master ~/.ssh/config: Host aliases, HostName, User, Port, IdentityFile, ProxyJump. Stop typing long SSH commands. One-line setup.
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Why the `latest` Docker Tag Is Lying to You
latest doesn't mean newest. Learn why pinning versions and digests matter for reproducible deployments.
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Why kill -9 Is the Wrong Default
Signals explained: SIGTERM vs SIGKILL, graceful shutdown, and when to actually use kill -9.
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