From df2a0478d05348957d78f9d2fe8200e6392c1e4c Mon Sep 17 00:00:00 2001
From: Tim Neumann <mail@timnn.me>
Date: Tue, 26 May 2015 22:18:56 +0200
Subject: [PATCH] add support for USERMAP_* env variables

---
 README.md | 20 ++++++++++++++++----
 start     | 15 +++++++++++++++
 2 files changed, 31 insertions(+), 4 deletions(-)

diff --git a/README.md b/README.md
index fe1a9ac..6be0ea5 100644
--- a/README.md
+++ b/README.md
@@ -8,11 +8,12 @@
 - [Reporting Issues](#reporting-issues)
 - [Installation](#installation)
 - [Quick Start](#quick-start)
-- [Creating User and Database at Launch](creating-user-and-database-at-launch)
+- [Creating User and Database at Launch](#creating-user-and-database-at-launch)
 - [Configuration](#configuration)
     - [Data Store](#data-store)
 - [Shell Access](#shell-access)
 - [Upgrading](#upgrading)
+- [Host UID / GID Mapping](#host-uid--gid-mapping)
 
 # Introduction
 
@@ -78,11 +79,10 @@ Run the postgresql image
 docker run --name postgresql -d sameersbn/postgresql:9.4
 ```
 
-The simplest way to login to the postgresql container as the administrative `postgres` user is to use the `--volumes-from` docker option to connect to the postgresql server over the unix socket.
+The simplest way to login to the postgresql container as the administrative `postgres` user is to use the `docker exec` command to attach a new process to the running container and connect to the postgresql server over the unix socket.
 
 ```bash
-docker run -it --rm --volumes-from=postgresql \
-  sameersbn/postgresql:9.4 sudo -u postgres -H psql
+docker exec -it postgresql sudo -u postgres psql
 ```
 
 # Creating User and Database at Launch
@@ -224,3 +224,15 @@ docker pull sameersbn/postgresql:9.4
 ```bash
 docker run --name postgresql -d [OPTIONS] sameersbn/postgresql:9.4
 ```
+
+# Host UID / GID Mapping
+
+Per default the container is configured to run postgres as user and group `postgres` with some unknown `uid` and `gid`. The host possibly uses these ids for different purposes leading to unfavorable effects. From the host it appears as if the mounted data volumes are owned by the host's user/group `[whatever id postgres has in the image]`.
+
+Also the container processes seem to be executed as the host's user/group `[whatever id postgres has in the image]`. The container can be configured to map the `uid` and `gid` of `postgres` to different ids on host by passing the environment variables `USERMAP_UID` and `USERMAP_GID`. The following command maps the ids to user and group `postgres` on the host.
+
+```bash
+docker run --name=postgresql -it --rm [options] \
+  --env="USERMAP_UID=$(id -u postgres)" --env="USERMAP_GID=$(id -g postgres)" \
+  sameersbn/postgresql:9.4
+```
diff --git a/start b/start
index 9c403f6..98ba492 100755
--- a/start
+++ b/start
@@ -6,6 +6,18 @@ PG_CONFDIR="/etc/postgresql/${PG_VERSION}/main"
 PG_BINDIR="/usr/lib/postgresql/${PG_VERSION}/bin"
 PG_DATADIR="${PG_HOME}/${PG_VERSION}/main"
 
+if [ -n "${USERMAP_UID}" ] || [ -n "${USERMAP_GID}" ]; then
+  if [ -n "${USERMAP_UID}" ] && [ -n "${USERMAP_GID}" ]; then
+    groupmod -g ${USERMAP_GID} postgres
+    usermod -u ${USERMAP_UID} -g ${USERMAP_GID} postgres
+  else
+    echo ""
+    echo "WARNING: "
+    echo "  Please specify USERMAP_UID AND USERMAP_GID or neither. Not changing user id..."
+    echo ""
+  fi
+fi
+
 # set this env variable to true to enable a line in the
 # pg_hba.conf file to trust samenet.  this can be used to connect
 # from other containers on the same host without authentication
@@ -16,6 +28,9 @@ DB_USER=${DB_USER:-}
 DB_PASS=${DB_PASS:-}
 DB_UNACCENT=${DB_UNACCENT:false}
 
+# fix ownership of ${PG_CONFDIR} (may be necessary if USERMAP_* was set)
+chown -R postgres:postgres ${PG_CONFDIR}
+
 # fix permissions and ownership of ${PG_HOME}
 mkdir -p -m 0700 ${PG_HOME}
 chown -R postgres:postgres ${PG_HOME}