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Connect Container's Filesystem To Computer's Filesystem

22 Jul 2020

Imagine we want to map important_file_in_container.txt inside the container with important_file.txt outside the container. For example, if we wanted to output the logs from a process inside the container to a log file outside the container.

Create File

Create a file (touch) called important_file.txt.

touch important_file.txt

Create Two Filepaths

# Create absolute filepath to file on computer filesystem
ORIGINAL=~/sandbox/docker/important_file.txt

# Create absolute path to where we want to create or replace
# a file inside the container
CONTAINER=/important_file_in_container.txt

Create Container With A Mount Bind

Create and start a detached (-d) Docker container (docker run) based on the Docker image nginx:latest called website (--name website). Create a mount bind point (--mount type=bind) connecting the file specified by ORIGINAL outside the container (src=${ORIGINAL}) with the file specified by CONTAINER inside the container (dst=${CONTAINER}).

docker run -d --name website --mount type=bind,src=${ORIGINAL},dst=${CONTAINER} nginx:latest

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SSH Into Container

Execute (docker exec) /bin/bash interactively (-it) on the Docker container called website.

docker exec -it website /bin/bash

[email protected]:/#

View Files And Folder In Container

View all files and folders (ls) that displays using long format and shows hidden files (-al)

Notice that important_file_in_container.txt exists inside the container. That is functionally the same file at important_file.txt outside the container.

ls -al

total 88
drwxr-xr-x   1 root root 4096 Aug  2 05:58 .
drwxr-xr-x   1 root root 4096 Aug  2 05:58 ..
-rwxr-xr-x   1 root root    0 Aug  2 05:58 .dockerenv
drwxr-xr-x   2 root root 4096 Jul 20 00:00 bin
drwxr-xr-x   2 root root 4096 May  2 16:39 boot
drwxr-xr-x   5 root root  340 Aug  2 05:58 dev
drwxr-xr-x   1 root root 4096 Jul 22 03:23 docker-entrypoint.d
-rwxrwxr-x   1 root root 1202 Jul 22 03:22 docker-entrypoint.sh
drwxr-xr-x   1 root root 4096 Aug  2 05:58 etc
drwxr-xr-x   2 root root 4096 May  2 16:39 home
-rw-r--r--   1 1000 1000    0 Aug  2 05:48 important_file_in_container.txt
drwxr-xr-x   1 root root 4096 Jul 22 03:23 lib
drwxr-xr-x   2 root root 4096 Jul 20 00:00 lib64
drwxr-xr-x   2 root root 4096 Jul 20 00:00 media
drwxr-xr-x   2 root root 4096 Jul 20 00:00 mnt
drwxr-xr-x   2 root root 4096 Jul 20 00:00 opt
dr-xr-xr-x 863 root root    0 Aug  2 05:58 proc
drwx------   2 root root 4096 Jul 20 00:00 root
drwxr-xr-x   1 root root 4096 Aug  2 05:58 run
drwxr-xr-x   2 root root 4096 Jul 20 00:00 sbin
drwxr-xr-x   2 root root 4096 Jul 20 00:00 srv
dr-xr-xr-x  13 root root    0 Aug  2 05:39 sys
drwxrwxrwt   1 root root 4096 Jul 22 03:23 tmp
drwxr-xr-x   1 root root 4096 Jul 20 00:00 usr
drwxr-xr-x   1 root root 4096 Jul 20 00:00 var