[Qemu-trivial] [PATCH] docs/devel/testing: Add -a option to usermod command on docker setup

[Murilo Opsfelder Araujo]

The option -G of usermod command will remove user from other groups
not listed, i.e.: $USER will belong only to group 'docker' after
following the documentation as is.

>From usermod(8) manual page:

    If the user is currently a member of a group which is not listed,
    the user will be removed from the group. This behaviour can be
    changed via the -a option, which appends the user to the current
    supplementary group list.

This patch improves the situation by adding the -a option to the
usermod command, which will just append user to the supplementary
group list.

Cc: address@hidden
Signed-off-by: Murilo Opsfelder Araujo <address@hidden>
---
 docs/devel/testing.rst | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/docs/devel/testing.rst b/docs/devel/testing.rst
index 18e2c0868a..135743a2bf 100644
--- a/docs/devel/testing.rst
+++ b/docs/devel/testing.rst
@@ -301,7 +301,7 @@ An alternative method to set up permissions is by adding 
the current user to
 .. code::
 
   $ sudo groupadd docker
-  $ sudo usermod $USER -G docker
+  $ sudo usermod $USER -a -G docker
   $ sudo chown :docker /var/run/docker.sock
 
 Note that any one of above configurations makes it possible for the user to
-- 
2.20.1