02/02: doc: Explain how to use psql with peer authentication.

[guix-commits]

ambrevar pushed a commit to branch master
in repository guix.

commit 1f0a41e95505c12af17c416651d70f18ea7c6a07
Author: Pierre Neidhardt <mail@ambrevar.xyz>
AuthorDate: Wed Jun 10 11:29:04 2020 +0200

    doc: Explain how to use psql with peer authentication.
    
    * doc/guix.texi (Database Services): Add example of shell commands to use 
psql
    as  system user.  Also add troubleshooting tip when service fails to start
    because of incompatible cluster.
---
 doc/guix.texi | 18 ++++++++++++++++++
 1 file changed, 18 insertions(+)

diff --git a/doc/guix.texi b/doc/guix.texi
index b2030e6..c23ed8d 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -17260,6 +17260,24 @@ The PostgreSQL daemon loads its runtime configuration 
from @var{config-file},
 creates a database cluster with @var{locale} as the default
 locale, stored in @var{data-directory}.  It then listens on @var{port}.
 
+If the services fails to start, it may be due to an incompatible
+cluster already present in @var{data-directory}.  Adjust it (or, if you
+don't need the cluster anymore, delete @var{data-directory}), then
+restart the service.
+
+Peer authentication is used by default and the @code{postgres} user
+account has no shell, which prevents the direct execution of @code{psql}
+commands as this user.  To use @code{psql}, you can temporarily log in
+as @code{postgres} using a shell, create a PostgreSQL superuser with the
+same name as one of the system users and then create the associated
+database.
+
+@example
+sudo -u postgres -s /bin/sh
+createuser --interactive
+createdb $MY_USER_LOGIN      # Replace appropriately.
+@end example
+
 @cindex postgresql extension-packages
 Additional extensions are loaded from packages listed in
 @var{extension-packages}.  Extensions are available at runtime.  For instance,