Having needed to update some Docker containers and getting familiar with how Docker works I though I would post this here so I have it for reference and if anyone else is looking to do the same thing.
On my installation of docker I run DotNet Core in containers and with each new update to the SDK new containers get published and it becomes necessary to update them every month or so.
As we can see on my installation at the moment the 2.2 versions are 4 months old
PS C:\WINDOWS\system32> docker images | findstr "dotnet"
mcr.microsoft.com/dotnet/core/sdk 3.0-buster 3930ade3a33a 4 days ago 695MB
mcr.microsoft.com/dotnet/core/aspnet 3.0-buster-slim 1d97a08ada5a 4 days ago 207MB
mcr.microsoft.com/dotnet/core/sdk <none> 4e9e8dec2900 3 weeks ago 707MB
mcr.microsoft.com/dotnet/core/aspnet <none> de4e4dcb9041 3 weeks ago 196MB
mcr.microsoft.com/dotnet/core/sdk 2.2 e268893be733 4 months ago 1.74GB
mcr.microsoft.com/dotnet/core/sdk 2.2-stretch e268893be733 4 months ago 1.74GB
mcr.microsoft.com/dotnet/core/aspnet 2.2-stretch-slim cb2dd04458bc 4 months ago 260MB
microsoft/dotnet 2.1-aspnetcore-runtime a5f99632e68d 4 months ago 253MB
mcr.microsoft.com/dotnet/core/aspnet 2.2 df2a085ca3a8 4 months ago 260MB
In order to update the container and make sure they are the latest version, I ran pull:
PS C:\WINDOWS\system32> docker pull mcr.microsoft.com/dotnet/core/sdk:2.2
2.2: Pulling from dotnet/core/sdk
9cc2ad81d40d: Pull complete
e6cb98e32a52: Pull complete
ae1b8d879bad: Pull complete
42cfa3699b05: Pull complete
dcc190332ff6: Pull complete
b49aea48d777: Pull complete
67e832fd5d6a: Pull complete
Digest: sha256:e1b19d391986f21b177c1ba47f8a8519bf5cff66a9459d04f3aea23e1a7ec30f
Status: Downloaded newer image for mcr.microsoft.com/dotnet/core/sdk:2.2
mcr.microsoft.com/dotnet/core/sdk:2.2
Now I have an update container for version 2.2 of the DotNet Core SDK
PS C:\WINDOWS\system32> docker images | findstr "dotnet"
mcr.microsoft.com/dotnet/core/sdk 2.2 08657316a4cd 4 days ago 1.74GB
This will update the container that is located locally and if you were having any problems simply restart any container that uses that particular container to gain the latest version. The concludes the update of the container.