Explanation of the "--update add" command for Alpine Linux
I'm trying to understand the Dockerfile https://hub.docker.com/r/rdsubhas/tor-privoxy-alpine/~/dockerfile/, which contains a RUN executive with
apk --update add privoxy tor@testing runit@testing
I wanted to check my understanding of how the apk command is being used, so I tried opening a terminal in the Alpine environment as follows:
docker run -it --rm alpine:latest /bin/ash
after which I simply ran apk to see its usage:
/ # apk
apk-tools 2.6.8, compiled for x86_64.
usage: apk COMMAND [-h|--help] [-p|--root DIR] [-X|--repository REPO]
[-q|--quiet] [-v|--verbose] [-i|--interactive] [-V|--version]
[-f|--force] [-U|--update-cache] [--progress] [--progress-fd FD]
[--no-progress] [--purge] [--allow-untrusted] [--wait TIME]
[--keys-dir KEYSDIR] [--repositories-file REPOFILE] [--no-network]
[--no-cache] [--arch ARCH] [--print-arch] [ARGS]...
The following commands are available:
add Add PACKAGEs to 'world' and install (or upgrade) them, while
ensuring that all dependencies are met
del Remove PACKAGEs from 'world' and uninstall them
fix Repair package or upgrade it without modifying main dependencies
update Update repository indexes from all remote repositories
info Give detailed information about PACKAGEs or repositores
search Search package by PATTERNs or by indexed dependencies
upgrade Upgrade currently installed packages to match repositories
cache Download missing PACKAGEs to cache and/or delete unneeded files
from cache
version Compare package versions (in installed database vs. available) or
do tests on literal version strings
index Create repository index file from FILEs
fetch Download PACKAGEs from global repositories to a local directory
audit Audit the directories for changes
verify Verify package integrity and signature
dot Generate graphviz graphs
policy Show repository policy for packages
stats Show statistics about repositories and installations
Global options:
-h, --help Show generic help or applet specific help
-p, --root DIR Install packages to DIR
-X, --repository REPO Use packages from REPO
-q, --quiet Print less information
-v, --verbose Print more information (can be doubled)
-i, --interactive Ask confirmation for certain operations
-V, --version Print program version and exit
-f, --force Do what was asked even if it looks dangerous
-U, --update-cache Update the repository cache
--progress Show a progress bar
--progress-fd FD Write progress to fd
--no-progress Disable progress bar even for TTYs
--purge Delete also modified configuration files (pkg
removal) and uninstalled packages from cache (cache
clean)
--allow-untrusted Install packages with untrusted signature or no
signature
--wait TIME Wait for TIME seconds to get an exclusive repository
lock before failing
--keys-dir KEYSDIR Override directory of trusted keys
--repositories-file REPOFILE Override repositories file
--no-network Do not use network (cache is still used)
--no-cache Read uncached index from network
--arch ARCH Use architecture with --root
--print-arch Print default arch and exit
This apk has coffee making abilities.
The thing is, I don't see the --update option in this documentation (only --update-cache).
What I suspect is that apk --update add [package] is simply shorthand for apk update followed by apk add [package]. Can anyone confirm this?
Answer
See https://github.com/gliderlabs/docker-alpine/pull/503
apk --update flag is really --update-cache.
Apk uses getopt_long (3), https://github.com/alpinelinux/apk-tools/blob/v2.10.3/src/apk.c#L574
So, --update flag is only abbreviated from --update-cache by getopt_long.
Long option names may be abbreviated if the abbreviation is unique or is an exact match for some defined option.