The docker attach command

The docker attach command attaches the running container and it is very helpful when you want to see what is written in stdout in real time:

$ sudo docker run -d --name=newtest alpine /bin/sh -c "while true; do sleep 2; df -h; done"
Unable to find image 'alpine:latest' locally
latest: Pulling from library/alpine
3690ec4760f9: Pull complete 
Digest: sha256:1354db23ff5478120c980eca1611a51c9f2b88b61f24283ee8200bf9a54f2e5c
1825927d488bef7328a26556cfd72a54adeb3dd7deafb35e317de31e60c25d67
$ sudo docker attach newtest
Filesystem                Size      Used Available Use% Mounted on
none                      7.7G      3.2G      4.1G  44% /
tmpfs                   496.2M         0    496.2M   0% /dev
tmpfs                   496.2M         0    496.2M   0% /sys/fs/cgroup
/dev/xvda1                7.7G      3.2G      4.1G  44% /etc/resolv.conf
/dev/xvda1                7.7G      3.2G      4.1G  44% /etc/hostname
/dev/xvda1                7.7G      3.2G      4.1G  44% /etc...