backup/snapshot! first!

checkout what releases are available:

imho one can only upgrade to the next release, not leaving out steps in between.

Alpine Linux 3.6.2
# current release running
cat /etc/alpine-release 

# release one wants to update to
cat /etc/apk/repositories

# get package definitions
apk update
v3.7.3-119-g356973950e []
v3.7.3-78-g634dbf6dd0 []
OK: 9132 distinct packages available

# do the upgrade
apk upgrade --available;
Upgrading critical system libraries and apk-tools:
(1/3) Installing libressl2.6-libcrypto (2.6.5-r0)
(2/3) Installing libressl2.6-libssl (2.6.5-r0)
(3/3) Upgrading apk-tools (2.7.6-r0 -> 2.10.1-r0)
Executing busybox-1.26.2-r11.trigger
Executing ca-certificates-20161130-r3.trigger
Continuing the upgrade transaction with new apk-tools:
ERROR: unsatisfiable constraints:
  /bin/sh (virtual):
    provided by: busybox
    required by: bash-4.4.19-r1[/bin/sh] ca-certificates-20190108-r0[/bin/sh] bash-4.4.19-r1[/bin/sh] fontconfig-2.12.6-r0[/bin/sh]
                 fontconfig-2.12.6-r0[/bin/sh] fontconfig-2.12.6-r0[/bin/sh] java-cacerts-1.0-r0[/bin/sh] fontconfig-2.12.6-r0[/bin/sh]
                 mkfontdir-1.0.7-r1[/bin/sh] pinentry-1.0.0-r0[/bin/sh] fontconfig-2.12.6-r0[/bin/sh] bash-4.4.19-r1[/bin/sh] fontconfig-2.12.6-r0[/bin/sh]
                 pinentry-1.0.0-r0[/bin/sh] alpine-baselayout-3.0.5-r2[/bin/sh] fontconfig-2.12.6-r0[/bin/sh] java-common-0.1-r0[/bin/sh]
                 ca-certificates-20190108-r0[/bin/sh] fontconfig-2.12.6-r0[/bin/sh] mkfontscale-1.1.2-r1[/bin/sh] fontconfig-2.12.6-r0[/bin/sh]
                 alpine-baselayout-3.0.5-r2[/bin/sh] fontconfig-2.12.6-r0[/bin/sh] ca-certificates-20190108-r0[/bin/sh] mkfontscale-1.1.2-r1[/bin/sh]

# solution is to install busybox package
apk add busybox
# and run the udate upgrade process again


“Alpine Linux is built around musl libc and busybox.

This makes it smaller and more resource efficient than traditional GNU/Linux distributions.

A container requires no more than 8 MB and a minimal installation to disk requires around 130 MB of storage.

Not only do you get a fully-fledged Linux environment but a large selection of packages from the repository.”