我有一个相当简单的 docker-compose.yml：
db:
build: docker/db
env_file:
- .env
ports:
- "5432"
web:
build: .
env_file:
- .env
volumes:
- .:/home/app/emerson
ports:
- "80:80"
links:
- db
Web 容器启动一个 rails 应用程序。一切都很顺利，但有一件事让我感到困惑。查看 Web 容器上的 /etc/hosts 内部，我看到以下条目：
172.17.0.10 db_1
172.17.0.10 emerson_db_1
172.17.0.10 db
我希望db，因为这是我要链接到Web容器的容器，但是其他人是从哪里来的？仅供参考，这是docker-compose up的输出：
Creating emerson_db_1...
Creating emerson_web_1...
Attaching to emerson_db_1, emerson_web_1
db_1 | The files belonging to this database system will be owned by user "postgres".
db_1 | This user must also own the server process.
db_1 |
db_1 | The database cluster will be initialized with locale "en_US.utf8".
db_1 | The default database encoding has accordingly been set to "UTF8".
db_1 | The default text search configuration will be set to "english".
db_1 |
db_1 | Data page checksums are disabled.
db_1 |
db_1 | fixing permissions on existing directory /var/lib/postgresql/data ... ok
db_1 | creating subdirectories ... ok
db_1 | selecting default max_connections ... 100
db_1 | selecting default shared_buffers ... 128MB
db_1 | selecting dynamic shared memory implementation ... posix
db_1 | creating configuration files ... ok
web_1 | *** Running /etc/my_init.d/00_configure_nginx.sh...
web_1 | *** Running /etc/my_init.d/00_regen_ssh_host_keys.sh...
web_1 | No SSH host key available. Generating one...
db_1 | ok
db_1 | initializing pg_authid ... ok
web_1 | Creating SSH2 RSA key; this may take some time ...
db_1 | initializing dependencies ... ok
web_1 | Creating SSH2 DSA key; this may take some time ...
web_1 | Creating SSH2 ECDSA key; this may take some time ...
web_1 | Creating SSH2 ED25519 key; this may take some time ...
db_1 | creating system views ... ok
db_1 | loading system objects' descriptions ... ok
db_1 | creating collations ... ok
db_1 | creating conversions ... ok
db_1 | creating dictionaries ... ok
db_1 | setting privileges on built-in objects ... ok
web_1 | invoke-rc.d: policy-rc.d denied execution of restart.
db_1 | creating information schema ... ok
web_1 | *** Running /etc/my_init.d/30_presetup_nginx.sh...
web_1 | *** Running /etc/rc.local...
db_1 | loading PL/pgSQL server-side language ... ok
web_1 | *** Booting runit daemon...
web_1 | *** Runit started as PID 98
db_1 | vacuuming database template1 ... ok
db_1 | copying template1 to template0 ... ok
db_1 | copying template1 to postgres ... ok
web_1 | Apr 24 02:44:26 1d3b7bb27612 syslog-ng[105]: syslog-ng starting up; version='3.5.3'
db_1 | syncing data to disk ... ok
db_1 |
db_1 | WARNING: enabling "trust" authentication for local connections
db_1 | You can change this by editing pg_hba.conf or using the option -A, or
db_1 | --auth-local and --auth-host, the next time you run initdb.
db_1 |
db_1 | Success. You can now start the database server using:
db_1 |
db_1 | postgres -D /var/lib/postgresql/data
db_1 | or
db_1 | pg_ctl -D /var/lib/postgresql/data -l logfile start
db_1 |
db_1 | ****************************************************
db_1 | WARNING: No password has been set for the database.
db_1 | This will allow anyone with access to the
db_1 | Postgres port to access your database. In
db_1 | Docker's default configuration, this is
db_1 | effectively any other container on the same
db_1 | system.
db_1 |
db_1 | Use "-e POSTGRES_PASSWORD=password" to set
db_1 | it in "docker run".
db_1 | ****************************************************
db_1 |
db_1 | PostgreSQL stand-alone backend 9.4.1
db_1 | backend> statement: ALTER USER "postgres" WITH SUPERUSER ;
db_1 |
web_1 | ok: run: /etc/service/nginx-log-forwarder: (pid 118) 0s
db_1 | backend>
db_1 | No PostgreSQL clusters exist; see "man pg_createcluster" ... (warning).
db_1 |
db_1 | backend> *******************************************
db_1 | LOG: database system was shut down at 2015-04-24 02:44:28 UTC
db_1 | LOG: database system is ready to accept connections
db_1 | LOG: autovacuum launcher started
web_1 | [ 2015-04-24 02:44:27.9386 119/7f4c07f13780 agents/Watchdog/Main.cpp:538 ]: Options: { 'analytics_log_user' => 'nobody', 'default_group' => 'nogroup', 'default_python' => 'python', 'default_ruby' => '/usr/bin/ruby', 'default_user' => 'nobody', 'log_level' => '0', 'max_pool_size' => '6', 'passenger_root' => '/usr/lib/ruby/vendor_ruby/phusion_passenger/locations.ini', 'passenger_version' => '4.0.58', 'pool_idle_time' => '300', 'temp_dir' => '/tmp', 'union_station_gateway_address' => 'gateway.unionstationapp.com', 'union_station_gateway_port' => '443', 'user_switching' => 'true', 'web_server_passenger_version' => '4.0.58', 'web_server_pid' => '107', 'web_server_type' => 'nginx', 'web_server_worker_gid' => '33', 'web_server_worker_uid' => '33' }
web_1 | [ 2015-04-24 02:44:27.0007 122/7f0c3eb9a780 agents/HelperAgent/Main.cpp:650 ]: PassengerHelperAgent online, listening at unix:/tmp/passenger.1.0.107/generation-0/request
web_1 | [ 2015-04-24 02:44:28.1065 127/7f5e5b4377c0 agents/LoggingAgent/Main.cpp:321 ]: PassengerLoggingAgent online, listening at unix:/tmp/passenger.1.0.107/generation-0/logging
web_1 | [ 2015-04-24 02:44:28.1072 119/7f4c07f13780 agents/Watchdog/Main.cpp:728 ]: All Phusion Passenger agents started!
但是只有两个容器docker ps -a输出：
CONTAINER ID IMAGE COMMAND CREATED STATUS PORTS NAMES
1d3b7bb27612 emerson_web:latest "/sbin/my_init" About an hour ago Up About an hour 443/tcp, 0.0.0.0:80->80/tcp emerson_web_1
0c047c3ce103 emerson_db:latest "/docker-entrypoint. About an hour ago Up About an hour 0.0.0.0:49156->5432/tcp emerson_db_1
此外，我还看到 web 容器中重复的环境变量，对应 db、db_1 和 emerson_db_1 前缀。