# still appear to the system as one single command # the `\` allows the command to be split over multiple lines, but # now let's start a new container, this time with a bind mount Now, let's bind mount this into a Docker container: # first let's stop the running container Into that file we add a single string: "hello world". We are in the /tmp/docker-test directory.įrom here we created a new file: my-file. This is all setup so we have something to see once we do the mount. We haven't done anything with Docker at this point. Next, we are going to use a "bind mount" to present the /var/ĭrwxrwxrwt 13 root root 36864 Sep 2 12:50. We've started a container, and by default the /var/www/madeup directory does not exist. Ls: cannot access '/var/www/madeup': No such file or directory $ docker exec ebc4a ls -la /var/www/madeup Any changes you make to the directory contents, or individual file will cause the file(s) to change on the Host machine. The differences become important outside of the running container.īind mounts allow you to take a directory or individual file that exists on your machine (from herein called the Host, or Docker Host) and access that directory or file inside the running container. What is the difference between a Docker Volume, and a Docker Bind Mount?įirst up, it's important to understand that however we choose to present (or mount) data into our running containers, from the perspective of the container, they all behave identically. I have never needed to use tmpfs, and as such have no further experience to share. tmpfs mounts are stored in the Docker host's memory and are never written to underlying storage. There is a third way of mounting data which is to use tmpfs mounts, which we won't be going into here. Enter: Docker VolumesĪs we shall soon see when we get to looking at docker-compose in more detail, there is a transition underway from the way Docker Volumes are currently predominantly used, to the 'new' way.Īs it happens, the 'new' way is not new at all.Ĭurrently most examples to be found online - and therefore most real world dev setups I've come across - tend to use bind mounts.Īnd the 'new' way is to actually use volumes. What appears a more optimal solution is to separate our Docker Containers from the data that these containers read from, and write too. In larger organisations where storage is centralised and optimised, this may make sysadmins unhappy. This is fine if all we ever do is stop and start that container.īut if the container is deleted, any data inside that container is also deleted.Īlso, as more data is added to a container, that container grows in size. However, the data inside a container exists only for the lifetime of that particular container instance. As we saw in the previous video, Docker Containers do allow the storage of persistent data.
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