blog.8-p.info

One of the development EC2 instances I wanted to collect some logs has ssm-agent instead of sshd. While this seems perfectly reasonable in 2020, how do you copy large log files from there? I initially did cat /some/large.log | gzip | base64 and carefully copied the base64-encoded output in System Manager’s in-browser terminal. It was stupid.

Instead, you can

  • Create an S3 bucket in your account.
  • Make a pre-sign URL to upload a file to the bucket.
  • Use curl to PUT a file to the pre-sign URL.

But there are a few caveats.

First AWS CLI cannot create a pre-sign URL with PUT. There is a PR since 2019, which hasn’t been merged. I ended up writing my own in Go.

Second curl’s -d parameter is removing \r and \n.

If you start the data with the letter @, the rest should be a file name to read the data from, or - if you want curl to read the data from stdin. Posting data from a file named ‘foobar’ would thus be done with -d, –data @foobar. When -d, –data is told to read from a file like that, carriage returns and newlines will be stripped out. If you don’t want the @ character to have a special interpretation use –data-raw instead.

I really don’t know why. I’ve been believing touching these characters is a Windows thing.