Docker quicktips #2

Heyyy just another small set of tricks I picked up over time when working with Docker.

Pull new versions of existing images / tags

docker images | awk 'BEGIN{OFS=":"} {print $1,$2}' | grep -v 'none' | grep -iv 'repo' | xargs -n1 docker pull

This chain of commands reformats the output of docker images to pull a new version of all tagged images on the host.

docker images should be self explanatory. Afterwards we use awk to build image:tag for each image on each line. We also want to skip images that are untagged (i.e. the tag reads ‘none’). Obviously we also want to drop the first line of the docker images command via inversely matching on ‘repo’. Last we pipe in each line separately (-n1) into a docker pull call.

We can use a similar approach to delete untagged images after upgrading and restarting all containers. (I.e. just grapping ‘none’ lines and feeding it into docker rmi)

docker images | grep '<none>' | awk '{print $3}' | xargs -n1 docker rmi

Add them to your .bashrc for convenience (NOTE: you need to escape special chars):

alias docker_update="docker images | awk 'BEGIN{OFS=\":\"} {print \$1,\$2}' | grep -v 'none' | grep -iv 'repo' | xargs -n1 docker pull"
alias docker_cleanup="docker images | grep '<none>' | awk '{print \$3}' | xargs -n1 docker rmi"

Restart all systemd managed docker containers

If we expand the unit files listed in docker quicktips #1 with PartOf= lines we can achieve services that ‘propagate’ restarts. See the systemd man pages for more info on PartOf=.

[winlu@winlu-main system]$ cat docker_nginx_reverse.service
Description=docker nginx_reverse proxy container

ExecStartPre=-/usr/bin/docker stop -t 2 nginx_reverse
ExecStartPre=-/usr/bin/docker rm nginx_reverse
ExecStart=/usr/bin/docker run --rm --name nginx_reverse -p 80:80 -p 443:443 -e -v /docker/nginx_reverse/certs:/etc/nginx/certs -v /docker/nginx_reverse/vhost.d:/etc/nginx/vhost.d:ro -v /var/run/docker.sock:/tmp/docker.sock jwilder/nginx-proxy