I'm trying to share files within a Docker guest using the volume sharing. In order to get the same UID, and therefore interoperability with those files, I would like to create a user in the Docker guest with the same UID as my own user.
In order to test out the idea, I wrote the following simplistic Dockerfile:
FROM phusion/baseimage
RUN touch /root/uid-$UID
Testing it with docker build -t=docktest . and then docker run docktest ls -al /root reveals that the file is simply named uid-.
Is there a means to share host environment variables with Docker during the guest build process?
The environment is not shared, you could use -e, --env options to set env variables in container.
I usually use this approach when I want to have the same owner of the mapped volume: I check uid & gid of directory in container and then create a corresponding user. Here my script (setuser.sh) which creates a user for a directory:
#!/bin/bash
setuser() {
if [ -z "$1" ]; then
echo "Usage: $0 <path>"
return
fi
CURRENT_UID=`id -u`
DEST_UID=`stat -c "%u" $1`
if [ $CURRENT_UID = $DEST_UID ]; then
return
fi
DEST_GID=`stat -c "%g" $1`
if [ -e /home/$DEST_UID ]; then
return
fi
groupadd -g $DEST_GID $DEST_GID
useradd -u $DEST_UID -g $DEST_GID $DEST_UID
mkdir -p /home/$DEST_UID
chown $DEST_UID:$DEST_GID /home/$DEST_UID
}
setuser $1
And this is the wrapper script which runs commands as the user, where the directory with permissions is specified either as $USER_DIR or in /etc/user_dir
#!/bin/bash
if [ -z "$USER_DIR" ]; then
if [ -e /etc/user_dir ]; then
export USER_DIR=`head -n 1 /etc/user_dir`
fi
fi
if [ -n "$USER_DIR" ]; then
if [ ! -d "$USER_DIR" ]; then
echo "Please mount $USER_DIR before running this script"
exit 1
fi
. `dirname $BASH_SOURCE`/setuser.sh $USER_DIR
fi
if [ -n "$USER_DIR" ]; then
cd $USER_DIR
fi
if [ -e /etc/user_script ]; then
. /etc/user_script
fi
if [ $CURRENT_UID = $DEST_UID ]; then
"$@"
else
su $DEST_UID -p -c "$@"
fi
P.S. Alleo suggested different approach: to map users and groups files into container and to specify uid and gid. So your container does not depend on built-in users/groups you could use it without additional scripts.
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