cmda

cmda

cmda (think: commander) is a CLI tool that can execute remote commands, including uploading local files/directories, to an AWS Lambda function. Along with EFS for Lambda, this makes it an easy tool to move files to/from an EFS file system that you might use with your other Lambda functions.

For example, here's how to run commands and copy local files to/from a filesystem mounted at /mnt/efs on a Lambda instance:

$ cmda upload ./mylocalfile.txt ./mylocaldir /mnt/efs/

$ cmda ls -l /mnt/efs/
total 12
drwxrwxr-x 2 sbx_user1051 495  4096 Jun 11 18:40 mylocaldir
-rw-r--r-- 1 sbx_user1051 495 10454 Jun 11 18:40 mylocalfile.txt

$ cmda sh -c 'echo hello > /mnt/efs/someremotefile.txt'

$ cmda mkdir /mnt/efs/someremotedir

$ cmda download /mnt/efs/someremotefile.txt /mnt/efs/someremotedir ./

cmda uses an S3 bucket as a staging area while it's uploading and downloading – the Lambda function and S3 bucket can be deployed easily using the installation instructions below.

Installation

You'll need Node.js installed, and then you can either install cmda globally:

npm install -g cmda
cmda [args...]

Or you can use npx (which comes with Node.js) to run it each time:

npx cmda [args...]

Lambda function

You'll need a Lambda function that understands cmda's commands. You can deploy one from the cmda application in the Serverless Application Repository.

You can optionally enter VPC details (like a security group and subnets) to have the function launch in an existing VPC when you create the application.

You can also add EFS filesystem details if you want to copy to/from EFS – just enter the EFS Access Point ID (you can find this from "Manage client access" on your filesystem in the EFS web console, eg fsap-1234abcd) and local mount path you want (eg /mnt/efs) in the given prompts.

After the application has been deployed, you'll need the name of the Lambda function it created, to configure cmda. You can get this by clicking on the CmdaFunction Resource in the Resources list, or by looking at the CloudFormation Stack's outputs for FunctionName.

It will look something like: serverlessrepo-cmda-CmdaFunction-12Q3L4R5I6O76

Configuration

cmda needs to know which function it's calling each time, which you can either do on the command line:

cmda --function my-CmdaFunction-1234 info

Or as an environment variable:

CMDA_FUNCTION=my-CmdaFunction-1234 cmda info

Or by saving it to your AWS config (~/.aws/config):

aws configure set cmda_function my-CmdaFunction-1234
cmda info

AWS profile

cmda will respect the AWS_PROFILE environment variable, or the --profile command line flag if you want to use a non-default AWS profile.

aws --profile my-profile configure set cmda_function my-CmdaFunction-1234
cmda --profile my-profile info

Multi-factor auth or SSO credentials

cmda doesn't support multi-factor auth codes itself, but it will try to read cached AWS CLI credentials, so if you make an API call with the AWS CLI, you should be able to subsequently use cmda with those credentials until they expire.

$ aws --profile my-mfa-profile sts get-caller-identity
Enter MFA code for arn:aws:iam::1234:mfa/michael: ****
$ cmda --profile my-mfa-profile info

Usage

Usage: cmda [--profile <profile>] [--function <fn>] [--bucket <bucket>] <cmd> [cmd options]

A command line tool for executing commands on, and copying files to/from AWS Lambda

Options:
--profile <profile>  AWS profile to use (default: AWS_PROFILE env or 'default')
--function <fn>      Lambda function name (default: CMDA_FUNCTION env or cmda_function from AWS CLI config)
--bucket <bucket>    S3 bucket to use for transfers (optional, will determine from Lambda if not given)
--verbose            More verbose output, especially for errors
--help               Display this help message
--version            Display command line version

Commands:
info                            Info about the cmda Lambda function and configured S3 bucket
exec <cmd> <opts>               Execute <cmd> <options> remotely on Lambda, eg 'exec ls -la'
cp|mv|rm|mkdir|ls|cat|touch|sh  Shortcuts for 'exec <cmd>'
upload <file1, ...> <dest>      Upload local files to <dest> on the Lambda filesystem (shortcut: ul)
download <file1, ...> <dest>    Download files from the Lambda filesystem to local <dest> (shortcut: dl)
create-vpc-endpoint             Creates a VPC endpoint to give the cmda Lambda function access to S3

Report bugs at github.com/lambci/cmda/issues