Month: June 2023

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Get standard error output from command on powershell

There could be times that you will need to get the standard output from a script or command in powershell and handle this information. An example that I use is the output of docker info which I use to monitor the service state along with other things. The output of the docker info will inform you about an error during connection if the engine is not working. In the latest version of docker they changed the way message is displayed and this information will be printed on standard error instead of standard output.

docker info

As a result when you try to find the connection state through a powershell command you will fail identifying the correct state.

 (docker info).Contains('ERROR: error during connect')

This behavior is noticed because the error is printed on standard error.

In order to bypass and get the standard error on the output, you will need to use 2>&1 along with the command.

docker info 2>&1

After that you can handle the output message appropriately.

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Downgrade docker by installing an older version on linux

Sometimes the latest version of software may include bugs that have not been fixed.This is the case for docker on Ubuntu 22.04. The buildkit version prints on stderr instead of stdout and this causes some issues on teamcity. As a solution I wanted to downgrade docker on a previous version. First you will need to delete the existing docker installation. You can do this with the below commands:

sudo apt-get purge -y docker-engine docker docker.io docker-ce docker-ce-cli docker-compose-plugin
sudo apt-get autoremove -y --purge docker-engine docker docker.io docker-ce docker-compose-plugin

sudo rm -rf /var/lib/docker /etc/docker
sudo rm /etc/apparmor.d/docker
sudo groupdel docker
sudo rm -rf /var/run/docker.sock

Based on your OS version you can go under docker downloads and find a specific version. Some older docker version exist for older OS versions but you can install them on later versions also.

Index of linux/ubuntu/dists/ (docker.com)

There could be a case when you have jammy (22.04) but you want to install binaries that were available on bionic version (18.04). In order to install an older version of docker you will need to download the old binaries by navigating inside the specific version then selecting pool and finally stable. Inside the last folder you can find all the architectures that are supported and you should select the appropriate one. For x64 you can select amd64 and then you can find a specific version of the binary.

In order to install specific version you will need to download all the packages that you need (some of them are dependencies of docker-ce) with wget and then install them.

Download:

wget https://download.docker.com/linux/ubuntu/dists/bionic/pool/stable/amd64/docker-scan-plugin_0.17.0~ubuntu-bionic_amd64.deb

Install:

dpkg -i docker-scan-plugin_0.17.0~ubuntu-bionic_amd64.deb
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Azure Keyvault Managed Identity C#

In the below .NET 6 example you can find how to get secrets from a keyvault using Managed Identity in order to secure communication between resources.

There are two packages required for this accomplishment.

https://www.nuget.org/packages/Azure.Identity

https://www.nuget.org/packages/Azure.Security.KeyVault.Secrets

Code:

using Azure.Identity;
using Azure.Security.KeyVault.Secrets;

const string managedIdentityIdentifier = "Id";
const string secretName = "secretName";
const string keyVaultUrl = "Url";

var client = new SecretClient(vaultUri: new Uri(keyVaultUrl), credential: new ManagedIdentityCredential(managedIdentityIdentifier));
var secret = client.GetSecret(secretName);

Console.WriteLine("retrieving secret value using managed identity: " + secret.Value.Value);