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--- wiki:advanced:multi-node:x2goserver-pgsql [2013/03/12 20:36]
sunweaver
+++ wiki:advanced:multi-node:x2goserver-pgsql [2016/03/29 19:40] (current)
stefanbaur [X2Go Server with PostgreSQL database backend]
@@ Line 1: / Line 1: @@
 ====== X2Go Server with PostgreSQL database backend ======
-**Note:** This wiki page explains how you can configure X2Go with PostgreSQL as database backend. However, this is only recommended for sites that run more than one X2Go Server (X2Go multi-node farms).
+**Note:** This wiki page explains how you can configure X2Go with PostgreSQL as database backend. However, for small setups, this is unneccessary. If you have one standalone X2Go server and only a small number of users, then you can use the SQLite database backend (which is the default after installation of the ''x2goserver'' package). The PostgreSQL backend is recommended for sites that run more than one X2Go Server (X2Go multi-node farms) and/or a large number of users.
-If you have one standalone X2Go server then please use the SQLite database backend (which is the default after installation of the ''x2goserver'' package).
 With X2Go Server v3.0.99.0 the whole session database backend code had been fully rewritten due to a serious security issue that had been brought up by Morty, Reinhard and Arw. Sind then, the ''sudo'' command is no longer required by ''x2goserver'' to neither contact the
@@ Line 13: / Line 12: @@
-  * configure PostgreSQL server to enable TCP connections from your X2go server host
+  * configure PostgreSQL server to enable TCP connections from your X2Go Server host
-  * configure PostgreSQL server for md5 authentication for users from x2goserver in
+  * configure PostgreSQL server for md5 authentication for users from X2Go Server in
 <code>
@@ Line 29: / Line 28: @@
 You must create a database user which can create databases and users for
-X2go database administration. You can also use the ''postgres'' user to do this
+X2Go database administration. You can also use the ''postgres'' user to do this
 job.
@@ Line 87: / Line 86: @@
 <code>
 $ /usr/lib/x2go/script/x2godbadmin --help
-X2Go SQL admin interface. Use it to create x2go database and insert or
+X2Go SQL admin interface. Use it to create the X2Go session database and insert or
-remove users or groups in x2go database
+remove users or groups in X2Go session database.
 Usage:
 x2godbadmin --createdb
@@ Line 96: / Line 96: @@
 </code>
-__Create database (evoke on X2go server):__
+==== Create database (evoke on X2Go server) ====
 <code>
@@ Line 102: / Line 103: @@
 </code>
-__Create database users:__
+==== Create database users ====
 <code>
@@ Line 112: / Line 114: @@
 </code>
-After that step users can create x2go sessions.
+After that step users of the posix group ''x2gousers'' can create X2Go sessions. Of course, any other group could be used here, as well.
+===== Database Structure and Troubleshooting =====
+In hopefully rare cases it may become necessary to fix the X2Go session database via standard PostgreSQL tools (e.g. ''psql''). This should not happen and please please please report the issue [[wiki:bugs|as a bug against the x2goserver]] X2Go component. However, if you are in the unlucky situation of having to fix up the session DB, then the below lines may render useful to you.
+==== Connect to the database ====
+In case it becomes necessary to edit the X2Go session database on the PostgreSQL server by hand, connect to the DB with this command:
+<code>
+$ psql --user x2godbuser --password -h localhost --dbname x2go_sessions
+</code>
+As password use the password found in ''/etc/x2go/x2gosql/passwords/x2goadmin''.
+After successful login, the ''psql'' PostgreSQL client shows these lines:
+<file>
+ts-01:~ # psql --user x2godbuser --password -h localhost --dbname x2go_sessions
+Password for user x2godbuser: <hidden>
+Welcome to psql <version>, the PostgreSQL interactive terminal.
+Type:  \copyright for distribution terms
+       \h for help with SQL commands
+       \? for help with psql commands
+       \g or terminate with semicolon to execute query
+       \q to quit
+x2go_sessions=>
+</file>
+==== Database structure ====
+The database has five tables:
+<file>
+x2go_sessions=> \dt
+             List of relations
+ Schema |     Name      | Type  |  Owner
+--------+---------------+-------+----------
+ public | messages      | table | postgres
+ public | mounts        | table | postgres
+ public | sessions      | table | postgres
+ public | used_ports    | table | postgres
+ public | user_messages | table | postgres
+(5 rows)
+</file>
+Three of them are important for session management: sessions, used_ports, mounts.
+Furthermore, the database defined four views:
+<file>
+x2go_sessions=> \dv
+            List of relations
+ Schema |     Name      | Type |  Owner
+--------+---------------+------+----------
+ public | mounts_view   | view | postgres
+ public | ports_view    | view | postgres
+ public | servers_view  | view | postgres
+ public | sessions_view | view | postgres
+(4 rows)
+x2go_sessions=>
+</file>
+If you want to show the content of a table or view, evoke this SQL command:
+<file>
+x2go_sessions=> select * from used_ports;
+    server    |              session_id               |   creator_id    | port
+--------------+---------------------------------------+-----------------+-------
+ ts-01 | mike-57-1379961697_stRTERMINAL_dp24 | x2gouser_mike | 30019
+ ts-01 | mike-57-1379961697_stRTERMINAL_dp24 | x2gouser_mike | 30018
+ ts-01 | mike-57-1379961697_stRTERMINAL_dp24 | x2gouser_mike | 30020
+(3 rows)
+</file>
+==== Troubleshooting ====
+If you want to remove these entries (because they are there but they by some reason should not be there), use this command set:
+<code>
+x2go_sessions=> delete from used_ports where port=30020;
+DELETE 1
+</code>
+... or ...
+<code>
+x2go_sessions=> delete from used_ports where session_id=mike-57-1379961697_stRTERMINAL_dp24;
+DELETE 3
+</code>
+For further input on manipulating PostgreSQL database via the ''psql'' client tool, see the PostgreSQL reference.

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