Thursday, July 14, 2016

Running modern python on Ubuntu LTS

The python version on your Ubunutu LTS may be slightly behind latest, or years behind, depending on the release cycle. Here's how to run a newer python without interfering with the system one.

Note that setting an install prefix is necessary to avoid making this the default system python (which will break cinnamon-settings apps as well as possibly other things). The prefix I chose puts it in a directory with my username.

Download the latest python source and install it:
sudo apt-get install build-essential libreadline-dev libsqlite3-dev
./configure --enable-ipv6 --enable-unicode=ucs4 --prefix=/usr/local/${USER}/
sudo make install
Your new python is now in /usr/local/${USER}/bin/python2.7. To use it, specify it in any virtualenvs you create. Make it an alias so you never forget:
alias virtualenv='virtualenv --python=/usr/local/${USER}/bin/python'

Tuesday, July 12, 2016

Run a different command on an existing docker container using exec

To run a previously created container with bash, start it as normal and then use exec (this assumes your original container can actually run successfully):
docker start [container id]
docker exec -it [container id] /bin/bash

Thursday, July 7, 2016

Creating a Google Cloud service account that can only create new objects in a single bucket

I wanted a service account that can only create new objects in a single bucket, and have those objects be publicly readable by default. Use case is a travis deployer that publishes build artifacts.
  1. create a service account. Currently this is under "IAM & Admin | Service Accounts" in the Google Cloud UI.
  2. In the IAM screen your service account is over-privileged, you can remove all privileges from the account here (which causes it to disappear from the IAM list). We will grant it permission over the bucket only.
  3. Create your bucket, then give the world access (you can also use AllUsers in the UI):
    gsutil defacl ch -u AllUsers:R gs://mybucket
  4. Give your writer access to the bucket. It seems there is no way to limit the permission to create only (options are read/write/owner).
  5. Test the permissions of your service account:
    gcloud auth activate-service-account --key-file mysecretfile.json serviceaccountname
    gcloud auth list
    # Check your service account is the active account, then try copying to the bucket you authorized, and another bucket which should fail.
    gsutil cp test gs://mybucket
    gsutil cp test gs://someotherbucket
  6. You can then set the default object permissions for the bucket via the UI so that new objects are world readable by default.