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https://github.com/timyiu478/sadservers

Notes of sad servers
https://github.com/timyiu478/sadservers

devops linux sre troubleshooting

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Notes of sad servers

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# Sad Servers



This repository is a collection of troubleshooting notes for server issues encountered in real-world scenarios. It serves as a reference for developers and system administrators facing similar challenges.



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# Notes



| #  | Title | Tags |

|----|-----------------------------------------------------|--------------------------------------------------|

| 1  | ["Tukaani": XZ LZMA Library Compromised](notes/xz_mzma_library_compromised.md) | `Shared Library` |

| 2  | ["Belo-Horizonte": A Java Enigma](notes/a_java_engima.md) | `Java`, `Swapping` |

| 3  | ["Florence": Database Migration Hell](notes/database_migration_hell.md) | `Database`, `Migration`, `Nginx` |

| 4  | ["Constanta": Jumping Frog](notes/jumping_frog.md) | `CTF`, `Hack`, `newgrp`, `SSH` |

| 5  | ["Roseau": Hack a Web Server](notes/hack_a_web_server.md) | `Hack`, `Web Server` |

| 6  | [Batumi: Troubleshoot "A" cannot connect to "B"](notes/troubleshoot_A_cannot_connect_to_B.md) | `iptables`, `Postgres`, `Systemd` |

| 7  | ["Karakorum": WTFIT – What The Fun Is This?](notes/wtfit.md) | `File Access Control`, `Web Server` |

| 8  | [Kihei: Surely Not Another Disk Space Scenario](notes/surely_not_another_disk_space_scenario.md) | `Disk`, `strace`, `LVM` |

| 9  | ["Jakarta": it's always DNS](notes/its_always_dns.md) | `DNS`, `Name Service Switch` |

| 10 | ["Pokhara": SSH and other sshenanigans](notes/ssh_and_other_sshenanigans.md) | `SSH`, `User Account` |

| 11 | ["Monaco": Disappearing Trick](notes/disapperaing_trick.md) | `Environment Variable`, `Hack`, `Git` |

| 12 | ["Depok": Nginx with Brotli](notes/nginx_with_brotli.md) | `Nginx`, `Compression` |

| 13 | ["Moyogalpa": Security Snag. The Trials of Mary and John](notes/security_snag.md) | `SSL`, `DNS`, `AppArmor` |

| 14 | [Bangalore: Envoy Panics](notes/envoy_panics.md) | `Envoy`, `Health Check`, `Forward Proxy`, `Panic Mode` |

| 15 | ["Minneapolis with a Vengeance": Break a CSV file](notes/break_a_csv_file_2.md) | `CSV`, `Data Processing`, `Scripting`, `Min Heap` |

| 16 | [Lisbon: etcd SSL cert troubles](notes/etcd_ssl_cert_troubles.md) | `etcd`, `SSL`, `iptables` |

| 17 | [Tarifa: Between Two Seas](notes/between_two_seas.md) | `Container`, `HAProxy`, `Nginx`, `Load Balancing` |

| 18 | [Melbourne: WSGI with Gunicorn](notes/wsgi_with_gunicorn.md) | `Nginx`, `Gunicorn`, `HTTP Header` |

| 19 | [Warsaw: Prometheus can't scrape the webserver](notes/prometheus_cant_scrape_the_webserver.md) | `Prometheus`, `Metric`, `HTTP Method` |

| 20 | [Atrani: Modify a SQlite3 Database](notes/modify_a_sqlite3_db.md) | `SQlite`, `Database`, `SQL` |

| 21 | ["Singara": Docker and Kubernetes web app not working.](notes/docker_and_k8s_web_app_not_working.md) | `Kubernetes`, `k3s`, `Node Port Range` |

| 22 | [Bengaluru: Kubernetes StatefulSet least known characteristic](notes/k8s_statefulSet_least_known_character.md) | `Kubernetes`, `At Most Once sematic of StatefulSet` |

| 23 | [Helsingør: The first walls of postgres physical replication](notes/first_walls_of_postgres_physical_replication.md) | `Postgres`, `Container`, `Replica` |

| 24 | [Buenos Aires: Kubernetes Pod Crashing](notes/k8s_pod_crashing.md) | `Kubernetes`, `Role Based Access Control` |

| 25 | ["Bern": Docker web container can't connect to db container.](notes/docker_web_container_cant_connect_to_db_container.md) | `Container`, `DNS` |

| 26 | [Salta: Docker container won't start.](notes/docker_container_wont_start.md) | `Container`, `Publishing ports` |

| 27 | [Manhattan: can't write data into database](notes/cant_write_data_into_database.md) | `Disk`, `Systemd`, `Postgres`, `Database` |

| 28 | [Tokyo: can't serve web file](notes/cant_serve_web_file.md) | `iptables`, `File Permissions` |

| 29 | [Cape Town: Borked Nginx](notes/borked_nginx.md) | `Nginx`, `Max Open File Descriptor Limits` |

| 30 | ["Hong-Kong": can't write data into database.](notes/hk_cant_write_data_into_database.md) | `Disk`, `Database`, `Postgres` |

| 31 | [Bilbao: Basic Kubernetes Problems](notes/basic_k8s_problem.md) | `Kubernetes`, `Scheduling` |

| 32 | ["Ivujivik": Parlez-vous Français?](notes/fix_csv.md) | `SQL`, `Data Processing`, `CSV` |

| 33 | [Bucharest: Connecting to Postgres](notes/connecting_to_postgres.md) | `Postgres`, `Database` |

| 34 | ["Manado": How much do you press?](notes/how_much_do_you_press.md) | `Compression` |

| 35 | [Geneva: Renew an SSL Certificate](notes/renew_ssl_cert.md) | `SSL`, `Reverse Proxy` |

| 36 | [Taipei: Come a-knocking](notes/come_a_knock.md) | `Port Knocking` |

| 37 | [Tokamachi: Troubleshooting a Named Pipe](notes/troubleshoot_a_named_pipe.md) | `Named Pipe`, `File Locking` |

| 38 | [Gitega: Find the Bad Git Commit](notes/find_bad_git_commit.md) | `Git` |

| 39 | [Saint John: what is writing to this log file?](notes/what_is_writing_to_this_log_file.md) | `List Of Open File` |

| 40 | [Oaxaca: Close an Open File](notes/close_an_open_file.md) | `List Of Open File` |

| 41 | [Saskatoon: counting IPs](notes/counting_ips.md) | `Data Processing` |

| 42 | [Hanoi: Find the Multitasking Users](notes/find_the_multitasking_users.md) | `Bash` |

| 43 | [Marrakech: Word Histogram](notes/word_histogram.md) | `Bash` |

| 44 | ["Bekasi": Supervisor is still around](notes/supervisor_is_still_around.md) | `Environment Variable` |

| 45 | [Apia: Needle in a Haystack](notes/needle_in_a_haystack.md) | `Diff`, `Checksum` |

| 46 | [Paris: Where is my webserver?](notes/where_is_my_web_server.md) | `Hack` |

| 47 | [Yokohama: Linux Users Working Together](notes/linux_users_working_together.md) | `Bash`, `Append-Only File` |

| 48 | [Lhasa: Easy Math](notes/easy_math.md) | `Scripting` |

| 49 | [Unimak Island: Fun with Mr Jason](notes/fun_with_mr_jason.md) | `json`, `Data Processing` |

| 50 | [Bata: Find in /proc](notes/find_in_proc.md) | `Data Processing` |

| 51 | [Minneapolis: Break a CSV file](notes/break_a_csv_file.md) | `CSV`, `Data Processing` |

| 52 | [Venice: Am I in a container?](notes/am_i_in_a_container.md) | `Container` |

| 53 | [Saint Paul: Merge Many CSVs files](notes/merge_many_csv_files.md) | `CSV`, `Data Processing` |

| 54 | ["Rosario": Restore a MySQL database](notes/restore_a_mysql_database.md) | `MySQL`, `Database`, `Backup` |

| 55 | ["Abaokoro": Restore MySQL Databases Spooked by a Ghost](notes/restore_mysql_db_spooked_by_a_ghost.md) | `MySQL`, `Database`, `Backup` |

| 56 | ["Chennai": Pull a Rabbit from a Hat](notes/pull_a_rabbit_from_a_hat.md) | `RabbitMQ`, `Environment Variables`, `Access Control` |

| 57 | [Bharuch: "Lost in Translation"](notes/lost_in_translation.md) | `Container`, `CPU Architecture`, `Emulator` |

| 58 | ["Quito": Control One Container from Another](notes/control_one_container_from_another.md) | `Container`, `Mount` |

| 59 | ["Budapest": User Creation](notes/user_creation.md) | `Bash` |

| 60 | ["Tokelau": Delete from history](notes/delete_from_history.md) | `Bash` |

| 61 | ["Zaragoza": Test changing critical files](notes/testing_change_critical_files.md) | `Mount` |