I have two Ubuntu 14 based PCs using a Viewsonic VG712s monitor via
KVM. One of the 'features' of this monitor is that the 'default'
monitor refresh rate of 60Hz loses up to about a cm's worth of screen
content off the left and right screen margins, whereas the 75Hz choice
displays correctly.
Unfortunately, whenever I install any flavour of Linux it always
chooses the 60Hz option as the systemwide setting, and usually, as in
Ubuntu 14, doesn't give the option of correcting this at installation
time, however in most previous versions of Linux I've been able to
work out how to correct it post installation, but not in Ubuntu 14.
I can set it manually for one session by ...
xrandr --output VGA1 --mode 1280x1024 --rate 75.0
... and I've also put this command in a script and checked that the
script is runnable and runs correctly. However of course this doesn't
correct the login screen or other users, neither does it survive a
reboot.
How in U14 can I *permanently* set the *systemwide* monitor resolution
and refresh rate? As a result of various internet searches, I've
tried:
1) Creating /etc/lightdm/lightdm.conf ...
[SeatDefaults]
display-setup-script=<above script>
... but no change.
2) Editing /usr/share/lightdm/lightdm.conf.d/50-ubuntu.conf to add a
line ...
display-setup-script=<above script>
... but this seems to replace the entire GUI configuration, so there
is no real functionality, and one is left navigating around system
alerts, and can never get to the login screen.
3) Editing /usr/share/lightdm/lightdm.conf.d/50-xserver-command.conf
to add a line ...
xserver-command=<above command>
... but the login screen never appears.
4) Installing compiz and making changes in there, but this seems to
have no effect even on the current session, let alone the system
defaults.
Other hits suggest, for example, editing xorg.conf, but these appear
to apply to older versions of Ubuntu, and in this version there is no
such file.
I've tried to work out how the GUI is initialised, but one ends up in
a maze of scripts calling other scripts, and finding the right
'pressure point' to insert a command such as the above is like
searching for the proverbial needle in a haystack.
I've been tearing out my hair about this in a struggle which has
lasted on and off for months or more. I can't believe that such a
trivial change, which is so simple to do in Windows, can be so
difficult/impossible in Ubuntu. Is anyone here knowledgeable enough
about the configuration path that is followed in bringing up X/lightdm
to know whereabouts a command such as the above could be effectively
called, and so preserve my rapidly vanishing sanity?
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