How to limit user to their home directory?

Question

I need to create a user that only has access to everything within their own home directory. For example, if their username is stash, then they would only have access within /home/stash.

Running on Linux (Raspbian)

I was thinking of making a group solely for this one user which took away permissions from every file and directory outside of their home directory but I'm not all too familiar with working with permissions in Linux.

Answer 1

If you will use SSH to login then a chroot can be an option ; let's support we have a user named testusr which will have as home directory /var/chroot/home/testusr :

Note that the above must be executed as root :

# Create the needed dirs
mkdir -p /var/chroot/{lib,lib64,etc,home,usr}
# Create the user account 
useradd -d /var/chroot/home/testusr testusr
echo "testusr:testusr" | chpasswd 
cd /var/chroot
# Create some basic dev nodes that will be needed by the terminal
mknod -m 666 null c 1 3
mknod -m 666 tty c 5 0
mknod -m 666 zero c 1 5
mknod -m 666 random c 1 8
#Make available the needed libraries
mount -o bind /lib /var/chroot/lib
mount -o bind /lib64 /var/chroot/lib64
mount -o bind /usr /var/chroot/usr
# Set the correct permissions
chown root:root /var/chroot
chmod 755 /var/chroot
# Set the jail on sshd daemon
cat <<EOF >> /etc/ssh/sshd_config
Match user testusr
    ChrootDirectory /var/chroot
EOF
# Restart sshd daemon
systemctl restart sshd
# Set the default shell for the user &  copy the content of /etc/group and /etc/passwd to the jail
usermod -s /usr/bin/bash testusr
cp /etc/{passwd,group} /var/chroot

Also note that the bind mounts should be permanent ( add them to /etc/fstab ) in case of this is not for a testing purpose.