DEV Community: Wajahat Ali Abid

bash: No such file or directory

Wajahat Ali Abid — Sat, 30 Mar 2024 18:43:03 +0000

I am using KDE Neon as my daily driver on my laptop. Recently due to KDE Neon update 6.0, there have been many bugs, but one as annoying as the one I faced the other day.

After system update, my bash stopped working completely. Granted I use zsh as my shell, bash is required by many programs on Linux. But everytime, I opened any such program, say pyenv, it just wouldn't work and give following error

/usr/bin/env: ‘bash’: No such file or directory linux

I looked into /usr/bin and couldn't find bash there. I couldn't install bash using dpkg or apt. This was pretty perplexing for me. Here is how I resolved the error with bash.

First of all, I edited the file /var/lib/dpkg/info/bash.prerm and changed first line to #! /bin/sh from #! /bin/bash

#! /bin/sh
set -e  

case "$1" in  
   upgrade)  
       update-alternatives --remove builtins.7.gz \  
           /usr/share/man/man7/bash-builtins.7.gz  
       ;;  

   remove|deconfigure)  
       ;;  

   failed-upgrade)  
       ;;  
   *)  
       echo "prerm called with unknown argument \`$1'" >&2  
       exit 1  
       ;;  
esac

Next I looked into /var/cache/apt/archives/ and found the file bash_5.1-6ubuntu1.1_amd64.deb. If you cannot find this file, you can download from here
Next I ran the command

sudo dpkg --force-remove-reinstreq -i /var/cache/apt/archives/bash_5.1-6ubuntu1.1_amd64.deb

This helped me restore the bash and helped me run programs again.

Stream Windows Event Logs to Cloudwatch

Wajahat Ali Abid — Mon, 04 Mar 2024 19:29:18 +0000

I received a requirement for sending Windows event logs to Amazon Cloudwatch because we wanted to monitor user activity on various Windows servers in our environment. There can be various other use cases for this requirement, however we will focus on setting up Windows event logs to Cloudwatch in this article.

To achieve this, we first need to install Amazon Cloudwatch Agent and then configure the server to push logs to Cloudwatch Logs.

Install Cloudwatch Agent

There are a couple of ways you can install Amazon Cloudwatch Agent on your servers.

Configure Iam Role

Create a policy CloudwatchAgentPolicyForWindowsLogging with following body



{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Sid": "CloudwatchLogsStatement",
            "Effect": "Allow",
            "Action": [
                "logs:CreateLogGroup",
                "logs:CreateLogStream",
                "logs:PutLogEvents",
                "logs:DescribeLogStreams"
            ],
            "Resource": [
                "arn:aws:logs:us-west-2:123456789012:log-group:windows-event-viewer-logs",
                "arn:aws:logs:us-west-2:123456789012:log-group:windows-event-viewer-logs:log-stream:*"
            ]
        }
    ]
}

Attach this policy to any server you want to enable Cloudwatch Logs on.

Configure Cloudwatch Agent

Go to C:\Program Files\Amazon\AmazonCloudWatchAgent and create a file config.json

Add logs section to Amazon Cloudwatch Agent configuration file.



{ 
    ...,
    "logs": {
        "logs_collected": {
            "windows_events": {
                "collect_list": [
                    {
                        "event_format": "xml",
                        "event_levels": [
                            "VERBOSE",
                            "INFORMATION",
                            "WARNING",
                            "ERROR",
                            "CRITICAL"
                        ],
                        "event_name": "System",
                        "log_group_name": "windows-event-viewer-logs",
                        "log_stream_name": "{instance_id}/System",
                        "retention_in_days": 365
                    },
                    {
                        "event_format": "xml",
                        "event_levels": [
                            "VERBOSE",
                            "INFORMATION",
                            "WARNING",
                            "ERROR",
                            "CRITICAL"
                        ],
                        "event_name": "Security",
                        "log_group_name": "windows-event-viewer-logs",
                        "log_stream_name": "{instance_id}/Security",
                        "retention_in_days": 365
                    }
                ]
            }
        }
    }
}

Open Powershell and run the following command



> cd 'C:/Program Files/Amazon/AmazonCloudWatchAgent/'
> ./amazon-cloudwatch-agent-ctl.ps1 -a fetch-config -m ec2 -c file:config.json -s

Start the Amazon Cloudwatch Agent Service and after some time, you'll see log stream created in the log group windows-event-viewer-logs.

Verify

Open Cloudwatch Logs and open the log group windows-event-viewer-logs.

Enable ContainerLogV2 on AKS

Wajahat Ali Abid — Wed, 28 Feb 2024 22:09:43 +0000

ContainerLogV2 provides additional data over ContainerLog (which is v1). The additional data includes

ContainerName
PodName
PodNamespace

To enable ContainerLogV2 on an existing AKS cluster, you need to create a configmap. Here's how you do this

Download the template ConfigMap YAML file for ContainerLog
Set containerlog_schema_version = "v2" in the yaml file
Update the exclude_namespaces under log_collection_settings.stdout and log_collection_settings.stderr as per your use case
Save the changes
Connect to Kubernetes cluster using CLI

kubectx my-cluster

Run the following command to create the configmap.

kubectl apply -f container-azm-ms-agentconfig.yaml

Done

I hope this helps. Refer to Container insights log schema and Configure data collection in Container insights using ConfigMap for more insights.

Yet another implementation for Slack Commands

Wajahat Ali Abid — Mon, 19 Sep 2022 13:27:48 +0000

We're using slack for communication within our team. Using slack slash commands, we also handle common day-to-day tasks like triggering deployments on different servers based on requirements. For a long time, that remained our primary use case, so we had a single AWS Lambda function taking care of this job, however, with the growing team and business, we felt the need to handle several other tasks this way. Thus we created a few more lambda functions that handled different tasks but the behavior among different lambda functions wasn't consistent, since every lambda was maintained separately.

General Idea

We decided to create a single lambda function that will be solely used for handling all the slash command requirements. The commands will follow a similar structure as normal shell commands do. Some examples are as follows

Command	Description
help	List down all the slash commands with usage
help deploy	List down help text for deploy commands, including all the options it takes and flags
deploy	Deploy for a specific client

Some examples of slack slash commands are as follows (assuming our slash command is /example)

/example help
/example help deploy
/example help deploy --client test-client --branch master

We can limit users who can issue a command as well as channels where the command can be issued from by using a very simple configuration

{
    "command": "deploy"
    "users": [
        "example.user"
    ],
    "channels": [
        "channel_id"
    ]
}

Implementation

We implemented this solution in python with the help of some useful packages from the open source community. Some of these packages are

Fast Api: For the implementation of the APIs
Mangum: For the integration of the Aws Lambda and the Api Gateway with the FastApi
Python Jenkins: For interacting with the Jenkins server that handles deployments
Argparse: For handling argument parsing

The way our implementation worked was as follows

The User sends a command via slack
Lambda function verifies
- If the command exists
- If the user is allowed to run the command
- If the command is allowed to be run from the specified channel
- If the command has all the required parameters

and responds appropriately

Execute the command and send the response back to the slack channel
Offload the long running commands to the Ecs container (e.g, database backup or restore)

The general architecture of this solution is as follows

This helps us implement new slack commands really quickly. All the error handling is similar across the different commands, so we don't need to handle the errors separately for every new command.