使用Docker Compose部署PostgreSQL后无法连接，提示postmaster.pid已存在

问题详情 #

使用docker-compose.yml部署PostgreSQL时，启动后无法连接，出现以下错误：

2022-10-10 11:19:41.820 UTC [43] FATAL:  lock file "postmaster.pid" already exists
2022-10-10 11:19:41.820 UTC [43] HINT:  Is another postmaster (PID 1) running in data directory "/var/lib/postgresql/data"?

我的docker-compose.yml配置： #

version: "3.9"
services:
  db:
    image: "postgres"
    restart: always
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
    ports:
      - '5432:5432'
    volumes:
      - /pgdata:/var/lib/postgresql/data

尝试的操作及日志： #

我用以下命令尝试连接运行中的容器：

docker exec -it -u postgres 31f122d6a413 postgres

容器日志显示卷冲突警告，且数据库已启动但无法连接：

Recreating test-docker-proj ... 
WARNING: Service "db" is using volume "/var/lib/postgresql/data" from the previous container. Host mapping "/pgdata" has no effect. 
Recreating test-docker-proj ... done
Attaching to test-docker-proj
db_1  | 
db_1  | PostgreSQL Database directory appears to contain a database; Skipping initialization
db_1  | 
db_1  | 2022-10-10 11:05:02.349 UTC [1] LOG:  starting PostgreSQL 14.5 on aarch64-unknown-linux-musl, compiled by gcc (Alpine 11.2.1_git20220219) 11.2.1 20220219, 64-bit
db_1  | 2022-10-10 11:05:02.349 UTC [1] LOG:  listening on IPv4 address "0.0.0.0", port 5432
db_1  | 2022-10-10 11:05:02.349 UTC [1] LOG:  listening on IPv6 address "::", port 5432
db_1  | 2022-10-10 11:05:02.352 UTC [1] LOG:  listening on Unix socket "/var/run/postgresql/.s.PGSQL.5432"
db_1  | 2022-10-10 11:05:02.356 UTC [22] LOG:  database system was shut down at 2022-10-10 10:47:01 UTC
db_1  | 2022-10-10 11:05:02.361 UTC [1] LOG:  database system is ready to accept connections

运行环境： #

• Mac Monterey M1
• docker-compose version 1.29.2

补充：可以用/bin/sh连接容器，但无法用postgres命令连接。

解决方案 #

1. 清理旧容器及关联卷 #

日志中的卷冲突警告说明之前的匿名卷未被清理，导致宿主机目录映射失效。执行以下命令彻底清理：

docker-compose down -v

-v参数会删除容器关联的所有卷，确保下次启动使用新的卷配置。

2. 删除残留的postmaster.pid锁文件 #

如果宿主机的/pgdata目录中残留了锁文件，手动删除：

sudo rm /pgdata/postmaster.pid

如果是容器内的卷残留，先进入容器再删除：

docker exec -it -u postgres <容器ID> /bin/sh
rm /var/lib/postgresql/data/postmaster.pid
exit
docker-compose restart

3. 优化Volume配置（推荐） #

Mac上直接使用绝对路径/pgdata可能存在权限问题，建议改用Docker命名卷管理数据：

version: "3.9"
services:
  db:
    image: "postgres"
    restart: always
    environment:
      - POSTGRES_USER=postgres
      - POSTGRES_PASSWORD=postgres
    ports:
      - '5432:5432'
    volumes:
      - pgdata:/var/lib/postgresql/data

# 定义命名卷
volumes:
  pgdata:

命名卷由Docker自动管理，权限适配更友好。

4. 正确连接容器内的PostgreSQL #

你使用的postgres命令是启动数据库服务的，而容器内已有运行的实例，应该用客户端工具psql连接：

# 方式1：指定用户进入psql
docker exec -it -u postgres <容器ID> psql

# 方式2：直接指定用户和数据库
docker exec -it <容器ID> psql -U postgres

内容的提问来源于stack exchange，提问作者sobmortin354