At /etc/apk/world, apk maintains the world, or list of explicitly installed packages. This is a plaintext file with one package spec per line.
If you edit this file manually, you should run apk-fix(8) to apply the changes.
Specifying a package name with no other modifiers will install the latest version of that package from the first repository in which it is available.
To pin a package to a tagged repository, use the format pkgname@tagname, e.g. busybox@edge. See apk-repositories(5) for details on tagged package repositories.
To constrain the acceptable versions of the package, use the =, <, >, >=, or ~= operators. Respectively, these require the package is equal to, less than, greater than, or greater than or equal to the specified version. The ~= operator constrains the package to the version numbers specified, but will not constrain any unspecified version numbers.
Installs busybox from the first repository from which it is available.
Installs busybox from the first repository tagged "edge" from which it's available. If busybox is not available in repositories with this tag, it will cause an error. When resolving dependencies of tagged requirements, untagged repositories are preferred, but repositories sharing the same tag will be considered if necessary.
Install busybox version 1.6.1.
Install a busybox version greater than 1.6.1.
Install a busybox version greater than or equal to 1.6.1.
Install a busybox version less than 1.6.1.
Install any busybox version between 1.6.0 (inclusive) and 1.7.0 (exclusive).
apk(8), apk-repositories(5), apk-upgrade(8).