Added group creation option and corresponding documentation (#76)

* Added group creation option and corresponding documentation.

Author: courtarro

README.md

@@ -8,7 +8,8 @@ Configure the container with the following environment variables or optionally m
 
 ### General Options
 
-- `SSH_USERS` list of user accounts and uids/gids to create. eg `SSH_USERS=www:48:48,admin:1000:1000:/bin/bash`. The fourth argument for specifying the user shell is optional
+- `SSH_USERS` list of user accounts and uids/gids to create. eg `SSH_USERS=www:48:48,admin:1000:1000:/bin/bash`. The fourth argument for specifying the user shell is optional. If `SSH_GROUPS` is omitted, a group is created for each user with the same name as the user.
+- `SSH_GROUPS` list of groups and gids to create. eg `SSH_GROUPS=guests:1005,other:1006`. Specifying this option disables automatic group creation of user-named groups if you also specify `SSH_USERS`.
 - `SSH_ENABLE_ROOT` if "true" unlock the root account
 - `SSH_ENABLE_PASSWORD_AUTH` if "true" enable password authentication (disabled by default) (excluding the root user)
 - `SSH_ENABLE_ROOT_PASSWORD_AUTH` if "true" enable password authentication for all users including root

entry.sh

@@ -79,6 +79,18 @@ if [ -w /etc/authorized_keys ]; then
     done
 fi
 
+# Add groups if SSH_GROUPS=group:gid set
+if [ -n "${SSH_GROUPS}" ]; then
+    GROUPZ=$(echo $SSH_GROUPS | tr "," "\n")
+    for G in $GROUPZ; do
+        IFS=':' read -ra GA <<< "$G"
+        _NAME=${GA[0]}
+        _GID=${GA[1]}
+        echo ">> Adding group ${_NAME} with gid: ${_GID}."
+        getent group ${_NAME} >/dev/null 2>&1 || groupadd -g ${_GID} ${_NAME}
+    done
+fi
+
 # Add users if SSH_USERS=user:uid:gid set
 if [ -n "${SSH_USERS}" ]; then
     USERS=$(echo $SSH_USERS | tr "," "\n")
@@ -99,7 +111,9 @@ if [ -n "${SSH_USERS}" ]; then
         else
             check_authorized_key_ownership /etc/authorized_keys/${_NAME} ${_UID} ${_GID}
         fi
-        getent group ${_NAME} >/dev/null 2>&1 || groupadd -g ${_GID} ${_NAME}
+        if [ -z "${SSH_GROUPS}" ]; then
+            getent group ${_NAME} >/dev/null 2>&1 || groupadd -g ${_GID} ${_NAME}
+        fi
         getent passwd ${_NAME} >/dev/null 2>&1 || useradd -r -m -p '' -u ${_UID} -g ${_GID} -s ${_SHELL:-""} -c 'SSHD User' ${_NAME}
     done
 else