https://www.youngju.dev/blog 천천히 올바르게. AI Researcher & DevOps Engineer Youngju's blog. GPU/CUDA, LLM, MLOps, Kubernetes AI workloads, and data engineering — plus mindset essays on confidence, routines, health, and sport psychology. ko fjvbn2003@gmail.com (Youngju Kim) fjvbn2003@gmail.com (Youngju Kim) Sat, 15 Aug 2026 00:00:00 GMT https://www.youngju.dev/blog/linux/2026-08-15-guide-backup-and-restore.en https://www.youngju.dev/blog/linux/2026-08-15-guide-backup-and-restore.en Starting from RPO and RTO, the criteria for choosing between rsync, tar, LVM snapshots, and snapshot-based backup tools. Covers the recovery rehearsal procedure and the five ways a backup quietly rots. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스백업복구재해복구운영rsync https://www.youngju.dev/blog/linux/2026-08-15-guide-backup-and-restore.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-backup-and-restore.ja RPOとRTOから出発して、rsync、tar、LVMスナップショット、スナップショットベースのバックアップツールを選ぶ基準を整理します。復旧リハーサルの手順と、バックアップが静かに壊れる五つの方式まで扱います。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스백업복구재해복구운영rsync https://www.youngju.dev/blog/linux/2026-08-15-guide-backup-and-restore https://www.youngju.dev/blog/linux/2026-08-15-guide-backup-and-restore RPO와 RTO에서 출발해 rsync, tar, LVM 스냅샷, 스냅샷 기반 백업 도구를 고르는 기준을 정리합니다. 복구 리허설 절차와 백업이 조용히 망가지는 다섯 가지 방식까지 다룹니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스백업복구재해복구운영rsync https://www.youngju.dev/blog/linux/2026-08-15-guide-dns.en https://www.youngju.dev/blog/linux/2026-08-15-guide-dns.en Splits name resolution into five separate segments — stub resolver through authoritative server — and works through record types, TTL and caching, delegation, reading dig output, propagation delay and stale caches, DNSSEC, and running DNS inside a company. Every command and rule here was checked against the RFC text and the manual pages. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스dns네트워크운영트러블슈팅dig https://www.youngju.dev/blog/linux/2026-08-15-guide-dns.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-dns.ja スタブリゾルバーから権威サーバーまで、名前解決の経路を区間ごとに分けたうえで、レコードタイプと TTL、委任、dig の読み方、伝播遅延とスタイルキャッシュ、DNSSEC、社内 DNS の運用までを整理します。コマンドとルールは RFC 原文とマニュアルで確認したものだけを載せました。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스dns네트워크운영트러블슈팅dig https://www.youngju.dev/blog/linux/2026-08-15-guide-dns https://www.youngju.dev/blog/linux/2026-08-15-guide-dns 스텁 리졸버부터 권한 서버까지 이름 해석 경로를 구간별로 나누고, 레코드 타입과 TTL, 위임, dig 출력 해석, 전파 지연과 스테일 캐시, DNSSEC, 사내 DNS 운영까지 정리합니다. 명령과 규칙은 RFC 원문과 매뉴얼에서 확인한 것만 실었습니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스dns네트워크운영트러블슈팅dig https://www.youngju.dev/blog/linux/2026-08-15-guide-file-descriptors-and-inodes.en https://www.youngju.dev/blog/linux/2026-08-15-guide-file-descriptors-and-inodes.en Starts from the relationship between inodes and directory entries and works through hard links, deleted-but-still-open files, inode exhaustion, and file descriptor limits. Covers why df and du diverge and how to recover, command by command. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스파일시스템inode파일디스크립터운영트러블슈팅 https://www.youngju.dev/blog/linux/2026-08-15-guide-file-descriptors-and-inodes.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-file-descriptors-and-inodes.ja inode とディレクトリエントリの関係から出発して、ハードリンク、削除された開きっぱなしのファイル、inode の枯渇、ファイルディスクリプタの上限までを整理します。df と du が食い違う理由と復旧方法をコマンド単位で扱います。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스파일시스템inode파일디스크립터운영트러블슈팅 https://www.youngju.dev/blog/linux/2026-08-15-guide-file-descriptors-and-inodes https://www.youngju.dev/blog/linux/2026-08-15-guide-file-descriptors-and-inodes inode와 디렉터리 엔트리의 관계에서 출발해 하드 링크, 삭제된 열린 파일, inode 고갈, 파일 디스크립터 한도까지 정리합니다. df와 du가 어긋나는 이유와 복구 방법을 명령 단위로 다룹니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스파일시스템inode파일디스크립터운영트러블슈팅 https://www.youngju.dev/blog/linux/2026-08-15-guide-firewall-and-access-control.en https://www.youngju.dev/blog/linux/2026-08-15-guide-firewall-and-access-control.en Starts from the structure of nftables and lays out what firewalld and ufw do on top of it. Covers the procedure that keeps you from locking yourself out while changing rules remotely, and the diagnostic order for when rules do not take effect. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스방화벽nftablesfirewalld보안네트워크 https://www.youngju.dev/blog/linux/2026-08-15-guide-firewall-and-access-control.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-firewall-and-access-control.ja nftablesの構造から出発し、firewalldとufwがその上で何をしているのかを整理します。リモートでルールを変更する際に自分自身を締め出さない手順と、ルールが適用されないときの診断順序を扱います。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스방화벽nftablesfirewalld보안네트워크 https://www.youngju.dev/blog/linux/2026-08-15-guide-firewall-and-access-control https://www.youngju.dev/blog/linux/2026-08-15-guide-firewall-and-access-control nftables의 구조에서 출발해 firewalld와 ufw가 그 위에서 무엇을 하는지 정리합니다. 원격에서 규칙을 바꾸다 스스로 잠기지 않는 절차와 규칙이 적용되지 않을 때의 진단 순서를 다룹니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스방화벽nftablesfirewalld보안네트워크 https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-performance-tools.en https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-performance-tools.en Interprets the numbers printed by top, vmstat, iostat, pidstat, sar and perf one column at a time. Covers which tool answers which question, which values create optical illusions, and the order in which to choose a tool using the USE method. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스성능모니터링운영sysstat명령어 https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-performance-tools.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-performance-tools.ja top、vmstat、iostat、pidstat、sar、perf が出力する数字を 1 列ずつ解釈します。どのツールがどの質問に答えるのか、どの値が錯覚を起こすのか、USE 方法論でツールを選ぶ順番までを整理しました。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스성능모니터링운영sysstat명령어 https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-performance-tools https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-performance-tools top, vmstat, iostat, pidstat, sar, perf가 찍어 주는 숫자를 한 열씩 해석합니다. 어떤 도구가 어떤 질문에 답하는지, 어떤 값이 착시를 일으키는지, USE 방법론으로 도구를 고르는 순서까지 정리했습니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스성능모니터링운영sysstat명령어 https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-troubleshooting-commands.en https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-troubleshooting-commands.en The diagnostic commands to run, in order, from the moment someone tells you a server is misbehaving. uptime, top, free, df, iostat, ss, journalctl — which number in each output to read, and what that number rules out versus what it leaves standing. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스트러블슈팅운영장애대응명령어성능 https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-troubleshooting-commands.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-troubleshooting-commands.ja サーバーの様子がおかしいと連絡を受けた瞬間から順番に実行する診断コマンドを整理します。uptime、top、free、df、iostat、ss、journalctlまで、各出力のどの数字を見るべきか、その数字が何を除外して何を残すのかを説明します。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스트러블슈팅운영장애대응명령어성능 https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-troubleshooting-commands https://www.youngju.dev/blog/linux/2026-08-15-guide-linux-troubleshooting-commands 서버가 이상하다는 연락을 받은 순간부터 순서대로 실행하는 진단 명령어를 정리합니다. uptime, top, free, df, iostat, ss, journalctl까지 각 출력의 어느 숫자를 봐야 하는지, 그 숫자가 무엇을 배제하고 무엇을 남기는지 설명합니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스트러블슈팅운영장애대응명령어성능 https://www.youngju.dev/blog/linux/2026-08-15-guide-logging-design.en https://www.youngju.dev/blog/linux/2026-08-15-guide-logging-design.en Designing the log plumbing of a Linux host, from journal retention policy to forwarding into rsyslog to the rotation modes of logrotate. Sets out the criteria for keeping the records an incident investigation needs without filling the disk. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스로그journaldrsysloglogrotate운영 https://www.youngju.dev/blog/linux/2026-08-15-guide-logging-design.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-logging-design.ja ジャーナルの保存ポリシー、rsyslog への転送、logrotate のローテーション方式まで、Linux ホストのログ配管を設計します。ディスクを埋めずに障害調査に必要な記録を残すための基準を整理します。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스로그journaldrsysloglogrotate운영 https://www.youngju.dev/blog/linux/2026-08-15-guide-logging-design https://www.youngju.dev/blog/linux/2026-08-15-guide-logging-design 저널의 보존 정책, rsyslog로의 전달, logrotate의 회전 방식까지 리눅스 호스트의 로그 배관을 설계합니다. 디스크를 채우지 않으면서 장애 조사에 필요한 기록을 남기는 기준을 정리합니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스로그journaldrsysloglogrotate운영 https://www.youngju.dev/blog/linux/2026-08-15-guide-process-and-signals.en https://www.youngju.dev/blog/linux/2026-08-15-guide-process-and-signals.en Signal numbers and default actions, the difference between SIGTERM and SIGKILL, zombies and orphans, process groups and sessions, nohup and setsid, and how to design a graceful shutdown. Traces the cause of a process that refuses to die, one layer at a time. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스프로세스시그널운영커널명령어 https://www.youngju.dev/blog/linux/2026-08-15-guide-process-and-signals.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-process-and-signals.ja シグナル番号と既定動作、SIGTERM と SIGKILL の違い、ゾンビと孤児、プロセスグループとセッション、nohup と setsid、そしてグレースフルシャットダウンを設計する方法までを整理します。死なないプロセスの原因を階層ごとに追跡します。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스프로세스시그널운영커널명령어 https://www.youngju.dev/blog/linux/2026-08-15-guide-process-and-signals https://www.youngju.dev/blog/linux/2026-08-15-guide-process-and-signals 시그널 번호와 기본 동작, SIGTERM과 SIGKILL의 차이, 좀비와 고아, 프로세스 그룹과 세션, nohup과 setsid, 그리고 우아한 종료를 설계하는 방법까지 정리합니다. 죽지 않는 프로세스의 원인을 계층별로 추적합니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스프로세스시그널운영커널명령어 https://www.youngju.dev/blog/linux/2026-08-15-guide-ssh.en https://www.youngju.dev/blog/linux/2026-08-15-guide-ssh.en sshd_config hardening, choosing and distributing key types, ProxyJump and port forwarding, and the layered order to debug a connection that will not come up, organised from an operator viewpoint. Includes the procedure that keeps you from locking yourself out while changing configuration. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스ssh보안운영서버관리네트워크 https://www.youngju.dev/blog/linux/2026-08-15-guide-ssh.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-ssh.ja sshd_config のハードニング、鍵の種類の選択と配布、ProxyJump とポートフォワーディング、接続できないときのデバッグ順序までを運用者の視点で整理します。設定を変更している最中に自分自身をロックアウトしないための手順も含みます。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스ssh보안운영서버관리네트워크 https://www.youngju.dev/blog/linux/2026-08-15-guide-ssh https://www.youngju.dev/blog/linux/2026-08-15-guide-ssh sshd_config 하드닝, 키 종류 선택과 배포, ProxyJump와 포트 포워딩, 접속이 안 될 때의 디버깅 순서까지 운영자 관점에서 정리합니다. 설정을 바꾸다 스스로 잠기지 않는 절차를 포함합니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스ssh보안운영서버관리네트워크 https://www.youngju.dev/blog/linux/2026-08-15-guide-tls-certificates.en https://www.youngju.dev/blog/linux/2026-08-15-guide-tls-certificates.en A purpose-by-purpose reference of the openssl commands for reading certificates, creating CSRs, verifying chains, converting formats, and diagnosing server connections. Also covers how to identify expiry, a missing chain, and a key mismatch in the field. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스tls인증서openssl보안운영 https://www.youngju.dev/blog/linux/2026-08-15-guide-tls-certificates.ja https://www.youngju.dev/blog/linux/2026-08-15-guide-tls-certificates.ja 証明書を読み、CSRを作り、チェーンを検証し、形式を変換し、サーバー接続を診断するopensslコマンドを目的別に整理します。有効期限切れとチェーン欠落、鍵の不一致を現場で判別する方法まで扱います。 Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스tls인증서openssl보안운영 https://www.youngju.dev/blog/linux/2026-08-15-guide-tls-certificates https://www.youngju.dev/blog/linux/2026-08-15-guide-tls-certificates 인증서를 읽고, CSR을 만들고, 체인을 검증하고, 형식을 변환하고, 서버 연결을 진단하는 openssl 명령을 목적별로 정리합니다. 만료와 체인 누락, 키 불일치를 현장에서 판별하는 방법까지 다룹니다. Sat, 15 Aug 2026 00:00:00 GMT fjvbn2003@gmail.com (Youngju Kim) 리눅스tls인증서openssl보안운영