『重用』容器名
但咱們在編寫/調試Dockerfile的時候咱們常常會重複以前的command，好比這種docker run --name jstorm-zookeeper zookeeper:3.4，而後就容器名就衝突了。java
$ docker run --name jstorm-zookeeper zookeeper:3.4 ... $ docker run --name jstorm-zookeeper zookeeper:3.4 docker: Error response from daemon: Conflict. The name "/jstorm-zookeeper" is already in use by container xxxxxxxxx
能夠在運行 docker run 時候加上--rm flag, 容器將在退出以後銷燬。無需手動docker rm CONTAINERlinux
$ docker run --name jstorm-zookeeper zookeeper:3.4 --rm # reuse $ docker create --name jstorm-zookeeper zookeeper:3.4 $ docker start jstorm-zookeeper # no error
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debug Dockerfile
在寫 Dockerfile 的時候，一般並不會一鼓作氣。有的時候容器啓動就crash 直接退出，有的時候build image 就會失敗，或者想驗證Dockerfile是否符合預期，咱們常常要debug Dockerfile。docker
若是build 失敗能夠直接 查看stdout的錯誤信息，拆分指令，從新build。shell
logs 查看 stdout
全部容器內寫到stdout的內容都會被捕獲到host中的一個history文件中, 能夠經過 docker logs CONTAINER 查看。segmentfault
$ docker run -d --name jstorm-zookeeper zookeeper:3.4 $ docker logs jstorm-zookeeper ZooKeeper JMX enabled by default Using config: /conf/zoo.cfg 2016-12-18 05:55:27,717 [myid:] - INFO [main:QuorumPeerConfig@124] - Reading configuration from: /conf/zoo.cfg 2016-12-18 05:55:27,725 [myid:] - INFO [main:DatadirCleanupManager@78] - autopurge.snapRetainCount set to 3 2016-12-18 05:55:27,725 [myid:] - INFO [main:DatadirCleanupManager@79] - autopurge.purgeInterval set to 0 2016-12-18 05:55:27,726 [myid:] - INFO [main:DatadirCleanupManager@101] - Purge task is not scheduled. 2016-12-18 05:55:27,728 [myid:] - WARN [main:QuorumPeerMain@113] - Either no config or no quorum defined in config, running in standalone mode 2016-12-18 05:55:27,746 [myid:] - INFO [main:QuorumPeerConfig@124] - Reading configuration from: /conf/zoo.cfg 2016-12-18 05:55:27,747 [myid:] - INFO [main:ZooKeeperServerMain@96] - Starting server 2016-12-18 05:55:27,766 [myid:] - INFO [main:Environment@100] - Server environment:zookeeper.version=3.4.9-1757313, built on 08/23/2016 06:50 GMT 2016-12-18 05:55:27,766 [myid:] - INFO [main:Environment@100] - Server environment:host.name=dbc742dd5688 2016-12-18 05:55:27,767 [myid:] - INFO [main:Environment@100] - Server environment:java.version=1.8.0_111-internal
即便是容器已經退出的也能夠看到，因此能夠經過這種方式來分析非預期的退出。這些文件一直保存着，直到經過docker rm把容器刪除。文件的具體路徑能夠經過docker inspect CONTAINER 得到。
（而後osx上你並找不到這些文件，由於其實osx的docker實際是運行在"VM"中，具體就不展開了，可是能夠經過 screen ~/Library/Containers/com.docker.docker/Data/com.docker.driver.amd64-linux/tty touch上"VM"的tty）api
在使用docker logs 的時候加一些參數來過濾log，默認輸出全部log。bash
Options:
--details Show extra details provided to logs -f, --follow Follow log output --help Print usage --since string Show logs since timestamp --tail string Number of lines to show from the end of the logs (default "all") -t, --timestamps Show timestamps
attach 實時查看stdout
若是你想實時查看容器的輸出你能夠用 docker attach CONTAINER 命令。jvm
默認會綁定stdin，代理signals， 因此若是你 ctrl-c 容器一般會退出。不少時候你們並不想這樣，只是想分離開，能夠ctrl-p ctrl-q。ide
執行任意command
能夠經過docker exec CONTAINER COMMAND，來在容器內執行任意 command，好比 cat 一些東西來debug。
$ docker run -d --name jstorm-zookeeper zookeeper:3.4 $ docker exec jstorm-zookeeper java -version openjdk version "1.8.0_111-internal" OpenJDK Runtime Environment (build 1.8.0_111-internal-alpine-r0-b14) OpenJDK 64-Bit Server VM (build 25.111-b14, mixed mode)
也能夠直接經過 exec 在容器內啓動一個 shell 更方便地調試容器，沒必要一條條執行docker exec。
$ docker exec -it jstorm-zookeeper /bin/bash bash-4.3# pwd /zookeeper-3.4.9
docker exec 只能在正在運行的容器上使用，若是已經中止了退出了就不行了，就只好用 docker logs了。
重寫entrypoint和cmd
每一個Docker鏡像都有 entrypoint 和 cmd , 能夠定義在 Dockerfile 中，也能夠在運行時指定。這兩個概念很容易混淆，並且它們的試用方式也不一樣。
entrypoint 比 cmd 更"高級"，entrypoint 做爲容器中pid爲1的進程運行（docker不是虛擬機，只是隔離的進程。真正的linux中pid爲1的是init）。cmd 只是 entrypoint的參數:
<ENTRYPOINT> "<CMD>"
當咱們沒有指定 entrypoint 時缺省爲 /bin/sh -c。因此其實 entrypoint 是真正表達這個docker應該幹什麼的，一般你們有一個shell 腳原本代理。entrypoint 和 cmd 均可以在運行的時候更改，經過更改來看這樣設置entrypoint是否優雅合理。
$ docker run -it --name jstorm-zookeeper --entrypoint /bin/bash zookeeper:3.4 bash-4.3# top Mem: 320212K used, 1725368K free, 89112K shrd, 35532K buff, 130532K cached CPU: 0% usr 0% sys 0% nic 100% idle 0% io 0% irq 0% sirq Load average: 0.20 0.06 0.02 5/195 7 PID PPID USER STAT VSZ %VSZ CPU %CPU COMMAND 1 0 root S 6220 0% 0 0% /bin/bash 7 1 root R 1516 0% 2 0% top
任何 docker run 命令中在image名後的內容都做爲cmd的內容傳給 entrypoint當參數。
暫停容器
使用 docker pause 能夠暫停容器中全部進程。這很是有用。
$ docker run -d --name jstorm-zookeeper zookeeper:3.4 && sleep 0.1 && docker pause jstorm-zookeeper && docker logs jstorm-zookeeper a24405a53ddd9b7d94d9e77fe2b5a67639a251d681aa2f34fcb0cc96f347ba48 jstorm-zookeeper ZooKeeper JMX enabled by default Using config: /conf/zoo.cfg 2016-12-18 16:17:47,720 [myid:] - INFO [main:QuorumPeerConfig@124] - Reading configuration from: /conf/zoo.cfg 2016-12-18 16:17:47,730 [myid:] - INFO [main:DatadirCleanupManager@78] - autopurge.snapRetainCount set to 3 2016-12-18 16:17:47,730 [myid:] - INFO [main:DatadirCleanupManager@79] - autopurge.purgeInterval set to 0 2016-12-18 16:17:47,730 [myid:] - INFO [main:DatadirCleanupManager@101] - Purge task is not scheduled. 2016-12-18 16:17:47,731 [myid:] - WARN [main:QuorumPeerMain@113] - Either no config or no quorum defined in config, running in standalone mode 2016-12-18 16:17:47,757 [myid:] - INFO [main:QuorumPeerConfig@124] - Reading configuration from: /conf/zoo.cfg 2016-12-18 16:17:47,757 [myid:] - INFO [main:ZooKeeperServerMain@96] - Starting server $ docker unpause jstorm-zookeeper && docker logs jstorm-zookeeper jstorm-zookeeper ZooKeeper JMX enabled by default Using config: /conf/zoo.cfg 2016-12-18 16:17:47,720 [myid:] - INFO [main:QuorumPeerConfig@124] - Reading configuration from: /conf/zoo.cfg 2016-12-18 16:17:47,730 [myid:] - INFO [main:DatadirCleanupManager@78] - autopurge.snapRetainCount set to 3 2016-12-18 16:17:47,730 [myid:] - INFO [main:DatadirCleanupManager@79] - autopurge.purgeInterval set to 0 2016-12-18 16:17:47,730 [myid:] - INFO [main:DatadirCleanupManager@101] - Purge task is not scheduled. 2016-12-18 16:17:47,731 [myid:] - WARN [main:QuorumPeerMain@113] - Either no config or no quorum defined in config, running in standalone mode 2016-12-18 16:17:47,757 [myid:] - INFO [main:QuorumPeerConfig@124] - Reading configuration from: /conf/zoo.cfg 2016-12-18 16:17:47,757 [myid:] - INFO [main:ZooKeeperServerMain@96] - Starting server 2016-12-18 16:18:09,039 [myid:] - INFO [main:Environment@100] - Server environment:zookeeper.version=3.4.9-1757313, built on 08/23/2016 06:50 GMT 2016-12-18 16:18:09,040 [myid:] - INFO [main:Environment@100] - Server environment:host.name=a24405a53ddd 2016-12-18 16:18:09,040 [myid:] - INFO [main:Environment@100] - Server environment:java.version=1.8.0_111-internal 2016-12-18 16:18:09,040 [myid:] - INFO [main:Environment@100] - Server environment:java.vendor=Oracle Corporation 2016-12-18 16:18:09,040 [myid:] - INFO [main:Environment@100] - Server environment:java.home=/usr/lib/jvm/java-1.8-openjdk/jre 2016-12-18 16:18:09,040 [myid:] - INFO [main:Environment@100] - Server environment:java.class.path=/zookeeper-3.4.9/bin/../build/classes:/zookeeper-3.4.9/bin/../build/lib/*.jar:/zookeeper-3.4.9/bin/../lib/slf4j-log4j12-1.6.1.jar:/zookeeper-3.4.9/bin/../lib/slf4j-api-1.6.1.jar:/zookeeper-3.4.9/bin/../lib/netty-3.10.5.Final.jar:/zookeeper-3.4.9/bin/../lib/log4j-1.2.16.jar:/zookeeper-3.4.9/bin/../lib/jline-0.9.94.jar:/zookeeper-3.4.9/bin/../zookeeper-3.4.9.jar:/zookeeper-3.4.9/bin/../src/java/lib/*.jar:/conf: 2016-12-18 16:18:09,040 [myid:] - INFO [main:Environment@100] - Server environment:java.library.path=/usr/lib/jvm/java-1.8-openjdk/jre/lib/amd64/server:/usr/lib/jvm/java-1.8-openjdk/jre/lib/amd64:/usr/lib/jvm/java-1.8-openjdk/jre/../lib/amd64:/usr/java/packages/lib/amd64:/usr/lib64:/lib64:/lib:/usr/lib 2016-12-18 16:18:09,041 [myid:] - INFO [main:Environment@100] - Server environment:java.io.tmpdir=/tmp 2016-12-18 16:18:09,041 [myid:] - INFO [main:Environment@100] - Server environment:java.compiler=<NA> 2016-12-18 16:18:09,043 [myid:] - INFO [main:Environment@100] - Server environment:os.name=Linux 2016-12-18 16:18:09,043 [myid:] - INFO [main:Environment@100] - Server environment:os.arch=amd64 2016-12-18 16:18:09,044 [myid:] - INFO [main:Environment@100] - Server environment:os.version=4.4.27-moby 2016-12-18 16:18:09,044 [myid:] - INFO [main:Environment@100] - Server environment:user.name=zookeeper 2016-12-18 16:18:09,044 [myid:] - INFO [main:Environment@100] - Server environment:user.home=/home/zookeeper 2016-12-18 16:18:09,044 [myid:] - INFO [main:Environment@100] - Server environment:user.dir=/zookeeper-3.4.9 2016-12-18 16:18:09,057 [myid:] - INFO [main:ZooKeeperServer@815] - tickTime set to 2000 2016-12-18 16:18:09,057 [myid:] - INFO [main:ZooKeeperServer@824] - minSessionTimeout set to -1 2016-12-18 16:18:09,058 [myid:] - INFO [main:ZooKeeperServer@833] - maxSessionTimeout set to -1 2016-12-18 16:18:09,076 [myid:] - INFO [main:NIOServerCnxnFactory@89] - binding to port 0.0.0.0/0.0.0.0:2181
top 和 stats 得到容器中進程的狀態
docker top CONTAINER 和在容器裏執行 top 的效果相似。
$ docker top jstorm-zookeeper PID USER TIME COMMAND 24593 dockrema 0:01 /usr/lib/jvm/java-1.8-openjdk/jre/bin/java -Dzookeeper.log.dir=. ..... $ docker stats jstorm-zookeeper CONTAINER CPU % MEM USAGE / LIMIT MEM % NET I/O BLOCK I/O PIDS jstorm-zookeeper 0.00% 24.86 MiB / 1.951 GiB 1.24% 648 B / 648 B 0 B / 0 B 20
經過 inspect 查看容器的詳細信息
docker inspect CONTAINER 飯後鏡像和容器的詳細信息。好比：
-
State —— 容器的當先狀態
-
LogPath —— history(stdout) file 的路徑
-
Config.Env —— 環境變量
-
NetworkSettings.Ports —— 端口的映射關係
環境變量很是有用不少問題都是環境變量引發的。
history 查看 image layers
能夠看到各層建立的指令，大小和哈希。能夠用來檢查這個image是否符合你的預期。