--no-cache 与 Alpine Dockerfile 的优点.rm/var/cache/apk/* [英] Alpine Dockerfile Advantages of --no-cache Vs. rm /var/cache/apk/*

问题描述

在使用 Alpine 镜像创建 Dockerfile 时，我经常看到使用 apk --no-cache 和其他时候它被提交，而是看到 rm/var/cache/apk/*.

When creating Dockerfiles using the Alpine image, I have often seen the use of the apk --no-cache and other times it is committed and instead I see rm /var/cache/apk/*.

我很想知道使用 --no-cache 消除了以后执行 rm/var/cache/apk/* 的需要.我还想知道一种风格是否比另一种风格更受青睐.

I am curious to know making use of the --no-cache eliminates the need to later do a rm /var/cache/apk/*. I would also like to know if one style is favored over another.

推荐答案

--no-cache 选项允许不在本地缓存索引，这对于保持容器较小很有用.

The --no-cache option allows to not cache the index locally, which is useful for keeping containers small.

从字面上看，它开头等于 apk update，结尾等于 rm -rf/var/cache/apk/*.

Literally it equals apk update in the beginning and rm -rf /var/cache/apk/* in the end.

我们使用 --no-cache 选项的一些例子:

Some example where we use --no-cache option:

$ docker run -ti alpine:3.7
/ # apk add nginx
WARNING: Ignoring APKINDEX.70c88391.tar.gz: No such file or directory
WARNING: Ignoring APKINDEX.5022a8a2.tar.gz: No such file or directory
ERROR: unsatisfiable constraints:
  nginx (missing):
    required by: world[nginx]
/ # 
/ # apk add --no-cache nginx
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
(1/2) Installing pcre (8.41-r1)
(2/2) Installing nginx (1.12.2-r3)
Executing nginx-1.12.2-r3.pre-install
Executing busybox-1.27.2-r7.trigger
OK: 6 MiB in 13 packages
/ # 
/ # ls -la /var/cache/apk/
total 8
drwxr-xr-x    2 root     root          4096 Jan  9 19:37 .
drwxr-xr-x    5 root     root          4096 Mar  5 20:29 ..

另一个我们不使用 --no-cache 选项的例子:

Another example where we don't use --no-cache option:

$ docker run -ti alpine:3.7
/ # apk add nginx
WARNING: Ignoring APKINDEX.70c88391.tar.gz: No such file or directory
WARNING: Ignoring APKINDEX.5022a8a2.tar.gz: No such file or directory
ERROR: unsatisfiable constraints:
  nginx (missing):
    required by: world[nginx]
/ # 
/ # apk update
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/main/x86_64/APKINDEX.tar.gz
fetch http://dl-cdn.alpinelinux.org/alpine/v3.7/community/x86_64/APKINDEX.tar.gz
v3.7.0-107-g15dd6b8ab3 [http://dl-cdn.alpinelinux.org/alpine/v3.7/main]
v3.7.0-105-g4b8b158c40 [http://dl-cdn.alpinelinux.org/alpine/v3.7/community]
OK: 9048 distinct packages available
/ # 
/ # apk add nginx
(1/2) Installing pcre (8.41-r1)
(2/2) Installing nginx (1.12.2-r3)
Executing nginx-1.12.2-r3.pre-install
Executing busybox-1.27.2-r7.trigger
OK: 6 MiB in 13 packages
/ # 
/ # ls -la /var/cache/apk/
total 1204
drwxr-xr-x    2 root     root          4096 Mar  5 20:31 .
drwxr-xr-x    6 root     root          4096 Mar  5 20:31 ..
-rw-r--r--    1 root     root        451508 Mar  3 00:30 APKINDEX.5022a8a2.tar.gz
-rw-r--r--    1 root     root        768680 Mar  5 09:39 APKINDEX.70c88391.tar.gz
/ # 
/ # rm -vrf /var/cache/apk/*
removed '/var/cache/apk/APKINDEX.5022a8a2.tar.gz'
removed '/var/cache/apk/APKINDEX.70c88391.tar.gz'

如您所见，这两种情况都是有效的.对我来说，使用 --no-cache 选项更优雅.

As you can see both cases are valid. As for me, using --no-cache option is more elegant.

这篇关于--no-cache 与 Alpine Dockerfile 的优点.rm/var/cache/apk/*的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！