Dockerfile 有如下内容，
FROM node:16.4.2-alpine3.14
WORKDIR /app
COPY package.json .
COPY . /app
并运行以下构建命令，
docker build -t app:0.1 .
花了28.4 秒，下面是终端日志，
[+] Building 28.4s (10/10) FINISHED => [internal] load build definition from Dockerfile 0.1s => => transferring dockerfile: 124B 0.0s => [internal] load .dockerignore 0.1s => => transferring context: 53B 0.0s => [internal] load metadata for docker.io/library/node:16.4.2-alpine3.14 17.1s => [auth] library/node:pull token for registry-1.docker.io 0.0s => [internal] load build context 0.1s => => transferring context: 2.01MB 0.0s => [1/4] FROM docker.io/library/node:16.4.2-alpine3.14@sha256:fabfca5e7dcb339097f998d6ef11c53dd80a3f99ed5cecc005e93d0ff6d4bda9 9.9s => => resolve docker.io/library/node:16.4.2-alpine3.14@sha256:fabfca5e7dcb339097f998d6ef11c53dd80a3f99ed5cecc005e93d0ff6d4bda9 0.0s => => sha256:fabfca5e7dcb339097f998d6ef11c53dd80a3f99ed5cecc005e93d0ff6d4bda9 1.00kB / 1.00kB 0.0s => => sha256:75dec02064547a8ec570f2953e8d68a1674ad3f37730160f1570cce077be9ed0 1.16kB / 1.16kB 0.0s => => sha256:40cb916373b08a087466d2e72402d0b3a4587fd3e9135169498cf0db4ff42a88 6.53kB / 6.53kB 0.0s => => sha256:5843afab387455b37944e709ee8c78d7520df80f8d01cf7f861aae63beeddb6b 2.81MB / 2.81MB 0.8s => => sha256:c118dce16b0057d713fc98e31606a84e4348fa2c967eaf1bb5fd21ba42825956 35.55MB / 35.55MB 7.1s => => sha256:aef8e8137ac43c8199343c96874993063af6584260f22b15e99f735cce5de653 2.35MB / 2.35MB 2.6s => => extracting sha256:5843afab387455b37944e709ee8c78d7520df80f8d01cf7f861aae63beeddb6b 0.2s => => sha256:ad336e0e52b8dfc38c23599663deb060b1ac169d548dec8072ead94712f708be 281B / 281B 2.0s => => extracting sha256:c118dce16b0057d713fc98e31606a84e4348fa2c967eaf1bb5fd21ba42825956 2.0s => => extracting sha256:aef8e8137ac43c8199343c96874993063af6584260f22b15e99f735cce5de653 0.2s => => extracting sha256:ad336e0e52b8dfc38c23599663deb060b1ac169d548dec8072ead94712f708be 0.0s => [2/4] WORKDIR /app 0.6s => [3/4] COPY package.json . 0.1s => [4/4] COPY . /app 0.1s => exporting to image 0.2s => => exporting layers 0.2s => => writing image sha256:91d93eddff55cba6bd8b72144b7320e025de93e9865177ff584c75b94d1bafc1 0.0s => => naming to docker.io/library/app:0.1
当我再次运行相同的构建命令时，需要 14.6 秒。
但是，如果我拉 node:16.4.2-alpine3.14 使用，
docker pull node:16.4.2-alpine3.14
然后运行build命令，那么build只需要0.3秒
我认为，当我们构建映像时，也会下载依赖项，这就是为什么花费的时间从 28.4 减少到 14.6 秒的原因。但为什么还要14.6 秒？它应该短至 0.3 秒。
为什么会这样？我错过了什么？
答案 0 :(得分：1)
以下可能是需要 18.4 秒的原因：
Dockerfile 的整个目录。某些文件或文件夹可能会占用大量空间，例如 {{ 1}}。对此的补救措施是将不需要的文件（例如 .git、node_module、日志文件）添加到 node_modules 文件中，以使 Docker 忽略某些文件。.dockerignore 命令检查解决 docker 注册表需要多长时间。dig 环境变量，例如：DOCKER_BUILDKIT=1