Update build and packaging docs.

1 files changed, 16 insertions, 7 deletions

diff --git a/packaging/readme.txt b/packaging/readme.txt
index 1f2d96cc..d6651774 100644
--- a/packaging/readme.txt
+++ b/packaging/readme.txt
@@ -14,11 +14,20 @@ socket from a userland device manager.  Accordingly, you probably
 want to set up a gpsd privilege group and make sure the Bluetooth
 device manager is in it.
 
-If you see problems with gpsd being unable to get write access to
-the USB or RS232 devices on your machine, it may be because after
-startup, when it drops privileges, it moves itself from root to the
-wrong group. gpsd normally figures out which group it should move
-to by looking at the ownership of a prototypical tty (look in gpsd.c
-for this code) but the owning user and group can be compiled in with
-build-system options.
+To avoid problems with gpsd not starting up properly when devices are
+hotplugged, make sure the installed gpsd will have read and write
+permissions on all serial devices that a GPS might be connected to (on
+Linux, this means at least /dev/ttyS*, /dev/ttyUSB*, and
+/dev/ttyACM*).
 
+The gpsd daemon needs to be started as root for best performance (it
+wants to nice itself, and needs root access to kernel PPS devices).
+But very soon after startup it drops privileges.  gpsd normally
+figures out which group it should move to by looking at the ownership
+of a prototypical tty (look in gpsd.c for this code) but the owning
+user and group can be compiled in with build-system options.
+
+Make sure whatever group gpsd lands in has dialout access - otherwise
+your users will see myerious failures.
+
+// end