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Short Description
Undertaker: a Garbage Collector for Docker Containers and Images
Full Description

docker-undertaker

Undertaker is a Garbage Collector for Docker Containers and Images.

It will remove containers which don't match any exclusion rule and are stopped longer than the configurated period of time (default: 3600 seconds = 1 hour). Images are removed if no excluded or active container references them anymore.

Main Use Case

Undertaker is meant for hosts with an extreme fluctuation of images and containers. Normally this are not your production machines, but developer, test and build hosts.

Important Notices

  • Undertaker will destroy Data Volumes with the Containers. Make sure you get your exclusions set up correctly!
  • If you run Undertaker not within the provided container, make sure that GNU grep is installed.

Usage

USAGE: ./undertaker [OPTIONS]

options:

  -i pattern   exclude matching images from destruction
  -c pattern   exclude matching containers from destruction
  -e           show processed exclude lists
  -E           show excluded containers and images
  -w seconds   wait time in seconds before destroying stopped containers
               (default: 3600)
  -x           PERFORM cleanup - for safety reasons no container or image
               removal is performed automatically unless you specify this flag
  -v           show version info and exit

NOTE: exclusion patterns will be processed with grep against the
      corresponding lists

environment variables:

  TRACE                 turn on line-level tracing
  UT_IMAGE_EXCLUDES     file containing image excludes
                        (default: /etc/undertaker/image-excludes)
  UT_CONTAINER_EXCLUDES file containing container excludes
                        (default: /etc/undertaker/container-excludes)
  UT_STILLWARM_SECONDS  how long will be containers ignored after exit,
                        same as option -w (default: 3600)

Running the Docker Container

Undertaker requires access to the docker socket to fullfill it's job, so you'll need to bind mount the socket to the container like this:

# replace X.Y.Z with fitting version (example: 0.3.0)
docker run --rm -v /var/run/docker.sock:/var/run/docker.sock tnussb/undertaker:X.Y.Z ... some options here

Undertaker is best used for one-shots: generate a container, run it once and destroy it. For automation add it as cron job.

Testing Exclusions

Exclusion rules can be best tested when you run the Undertaker container like this:

# -e    ... show active exclusions
# -E    ... show excluded containers and images
# -w 0  ... don't ignore any stopped containers

# make sure you don't use the flag -x!  ... and replace X.Y.Z with fitting version
docker run --rm -v /var/run/docker.sock:/var/run/docker.sock tnussb/undertaker:X.Y.Z -eE -w 0 \
  -c my-excluded-container1 \
  -c my-excluded-container2 \
  -i my-included-image1 \
  -i my-included-image2

Crafting Exclusions

Container and image excludes are processed with grep, against a list of possible targets. Each line of the target list starts with the long id followed by a space and name.

examples of target lists:

## container target list

12b4b301124823882bc25296176b618066cc6feb4ee62b8e6cf7bac6cc0b9e79 a-test3-cont
819be7d134f052e035052e2c76d8c73a5416e0f16e04254d5537873e0781befc test1-container
987ebebdbec2f4a67fdd0e86250c1576a20e847ca8d31f652e3826ce07c00233 test2-cont
aff4ca67e1c50952b37819f2223505daa2ceae55c691779f359f893c6f1f6df2 test3-cont

## image target list

0357abd8c386ac423438e10effb00c16b9de4208cbc1f0af584a5b5cf444593d tnussb/undertaker:0.3.0
31f630c65071968699d327be41add2e301d06568a4914e1aa67c98e1db34a9d8 alpine:latest
5bd56d818842eb61485761c291fb1393b0a6fb827ad4ff21223ae026df9c7203 gliderlabs/alpine:3.2
8c2e06607696bd4afb3d03b687e361cc43cf8ec1a4a725bc96e39f05ba97dd55 busybox:latest

Here are some exclusion strings and what they will match:

-c test    # will match all (substring is part of each name)
-c 'ner$'  # matches test1.container (ends with 'ner')
-c ' test' # maches test1-container, test2-cont and test3-cont (NOTE the space!)
-c '3'     # STUPID one: matches all
-c '^12b4b3011248' # when matching short ids DONT FORGET the caret (^) to match
                   # ids starting with the given digits !

Handling large exclusion lists

If you need to handle a large list of exclusions you can either mount your own files to /etc/undertaker/image-excludes and container-excludes or mount a Data Volume to /etc/undertaker.

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