docker-debugging

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🇨🇳

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Docker Debugging Skill

Docker调试技能

Master container debugging and troubleshooting for development and production issues.

掌握面向开发与生产环境问题的容器调试与故障排查方法。

Purpose

用途

Diagnose and resolve container issues including crashes, performance problems, networking failures, and resource constraints.

诊断并解决各类容器问题，包括崩溃、性能问题、网络故障以及资源受限等。

Parameters

参数

Parameter	Type	Required	Default	Description
container	string	No	-	Container name/ID
issue_type	enum	No	-	crash/network/resource/health
verbose	boolean	No	false	Detailed output

参数	类型	是否必填	默认值	描述
container	string	否	-	容器名称/ID
issue_type	enum	否	-	crash/network/resource/health
verbose	boolean	否	false	详细输出

Debugging Commands

调试命令

Container Logs

容器日志

bash

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bash

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Last 100 lines

最后100行

docker logs --tail 100 <container>

Follow logs

实时跟踪日志

docker logs -f <container>

With timestamps

显示时间戳

docker logs -t <container>

Specific time range

指定时间范围

docker logs --since 1h --until 30m <container>

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docker logs --since 1h --until 30m <container>

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Interactive Debugging

交互式调试

bash

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bash

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Execute shell in running container

在运行中的容器内执行shell

docker exec -it <container> /bin/sh

As root (for debugging)

以root身份执行（用于调试）

docker exec -u 0 -it <container> /bin/sh

Run command

执行命令

docker exec <container> ps aux

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docker exec <container> ps aux

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Container Inspection

容器检查

bash

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bash

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Full inspection

完整检查信息

docker inspect <container>

Specific fields

查看特定字段

docker inspect --format='{{.State.Status}}' <container> docker inspect --format='{{.State.Health.Status}}' <container> docker inspect --format='{{json .NetworkSettings}}' <container>

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docker inspect --format='{{.State.Status}}' <container> docker inspect --format='{{.State.Health.Status}}' <container> docker inspect --format='{{json .NetworkSettings}}' <container>

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Issue Diagnosis

问题诊断

Container Won't Start

容器无法启动

bash

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bash

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Check exit code

检查退出码

docker inspect --format='{{.State.ExitCode}}' <container>

View last logs

查看最新日志

docker logs --tail 50 <container>

Check events

查看事件记录

docker events --filter 'container=<name>' --since 1h

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docker events --filter 'container=<name>' --since 1h

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Exit Code Reference

退出码参考

Code	Meaning	Action
0	Success	Normal exit
1	General error	Check logs
137	OOMKilled	Increase memory
139	Segfault	Check app code
143	SIGTERM	Graceful shutdown

代码	含义	操作建议
0	成功	正常退出
1	一般错误	查看日志
137	内存不足被终止	增加内存配额
139	段错误	检查应用代码
143	接收到SIGTERM信号	优雅关闭

Health Check Failures

健康检查失败

bash

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bash

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Check health status

检查健康状态

docker inspect --format='{{json .State.Health}}' <container>

View health logs

查看健康检查日志

docker inspect --format='{{range .State.Health.Log}}{{.Output}}{{end}}' <container>

Manually test health

手动测试健康状态

docker exec <container> curl -f http://localhost/health

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docker exec <container> curl -f http://localhost/health

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Resource Issues

资源问题

bash

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bash

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Live stats

实时资源统计

docker stats <container>

Formatted output

格式化输出

docker stats --format "table {{.Name}}\t{{.CPUPerc}}\t{{.MemUsage}}\t{{.NetIO}}"

Check limits

查看资源限制

docker inspect --format='{{.HostConfig.Memory}}' <container>

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docker inspect --format='{{.HostConfig.Memory}}' <container>

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Network Issues

网络问题

bash

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bash

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Check network

检查网络配置

docker network inspect <network>

Test DNS

测试DNS解析

docker exec <container> nslookup <service>

Test connectivity

测试连通性

docker exec <container> ping -c 3 <target> docker exec <container> curl http://<service>:port

View ports

查看端口映射

docker port <container>

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docker port <container>

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Troubleshooting Flowchart

故障排查流程图

Container Issue?
│
├─ Won't Start
│  ├─ Check logs: docker logs <c>
│  ├─ Check exit code: docker inspect
│  └─ Verify image: docker pull
│
├─ Unhealthy
│  ├─ Check health logs
│  ├─ Test health endpoint manually
│  └─ Increase start_period
│
├─ High Resource
│  ├─ Check stats: docker stats
│  ├─ Increase limits
│  └─ Profile application
│
└─ Network Failed
   ├─ Check DNS: nslookup
   ├─ Check connectivity: ping/curl
   └─ Verify network membership

遇到容器问题？
│
├─ 无法启动
│  ├─ 查看日志：docker logs <c>
│  ├─ 检查退出码：docker inspect
│  └─ 验证镜像：docker pull
│
├─ 状态不健康
│  ├─ 查看健康检查日志
│  ├─ 手动测试健康端点
│  └─ 延长启动等待时间（start_period）
│
├─ 资源占用过高
│  ├─ 查看统计数据：docker stats
│  ├─ 调整资源限制
│  └─ 应用性能分析
│
└─ 网络故障
   ├─ 检查DNS解析：nslookup
   ├─ 测试连通性：ping/curl
   └─ 验证网络成员身份

Debug Container

调试容器

bash

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bash

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Run debug container in same network

在同一网络中运行调试容器

docker run --rm -it --network <network>
nicolaka/netshoot

Available tools: curl, dig, nmap, tcpdump, etc.

可用工具：curl、dig、nmap、tcpdump等

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Error Handling

错误处理

Common Errors

常见错误

Error	Cause	Solution
`container not found`	Wrong name/ID	Use `docker ps -a`
`exec failed`	Container stopped	Start container first
`no such file`	Missing binary	Use correct image

错误信息	原因	解决方案
`container not found`	名称/ID错误	使用 `docker ps -a` 查看正确信息
`exec failed`	容器已停止	先启动容器
`no such file`	缺少二进制文件	使用正确的镜像

Usage

使用方法

Skill("docker-debugging")

Skill("docker-debugging")