icyrock.com's questions

I'm running Xubuntu 14.10, currently using lightdm. Let's examine two process trees:

init───lightdm───lightdm───upstart───xfce4-terminal───bash

and:

init───lightdm───lightdm───upstart───emacs─┬─{dconf worker}
                                           ├─{gdbus}
                                           └─{gmain}

My issue is that I am setting PATH in .bashrc, which given that emacs is started by upstart (using the keyboard shortcut), makes it not have the same PATH value. (I know I should move that to .bash_profile or so, but that won't fix the issue and it's fine given that I usually login in one way only, through X / lightdm.)

Consider these three cases:

• Terminal on vty1 -> bash - path is initialized by bash (.bash_profile)
• X -> emacs - path is initialized by lightdm (.xinitrc)
• X -> xfce4-terminal -> bash - path is initialized by lightdm (.xinitrc), then modified by bash (.bash_profile)

First - is the above correct or are there other things happening? Or better yet - should I be using the above to initialize or some other files / mechanisms?

If the above is correct, I assume putting PATH in a script, then calling from both .bash_profile and .xinitrc would be the best way to sync up all these environments, correct?

Are there hooks that provide a way to reset the PATH of lightdm? I'd like to avoid logging in and out when changing PATH if possible.

Is there a way to query monitor information from command line? For example, get monitor model, similar to e.g. what lspci does for graphic card info, or whether it's currently on or off, things like that.

If possible, what kinds of basic information such as the above can be easily gathered? For example, is it possible to determine if monitor is in portrait or landscape position? Or if it has built-in speakers or not?

Command line is the preference, but if there's a GUI method, I'd like to hear about it, too.

I see that Ubuntu uses /etc/cron.{daily,weekly,monthly} for cron jobs. I also see that some things, like updatedb from mlocate, put their jobs there:

$ dpkg -L mlocate|grep y/m
/etc/cron.daily/mlocate

Somtetimes, I would like to disable some of these jobs (mlocate in this case). I can obviously sudo mv /etc/cron.daily/mlocate ~/cron.daily-dont-run and be over with it. However, two questions:

• Is this how this gets managed? Is there something like service to manage SysV init scripts or overrides such as described in Upstart intro, 10.41.1 Override Files? I would like to tell it "OK, I don't want you to start", but without touching what is installed (see next item for one of the reasons)
• If I delete and then reinstall mlocate, I'll again get the cron.daily entry. Also, I guess (is this true?) upgrades will probably not go smoothly (e.g. it will make a cron.daily entry or maybe possibly break the package if there's something in the cron entry that it depends on).

If you do, how do you manage / deal with the things such as the above?

When I suspend the laptop, the USB devices are left on. I don't mind this in general, however I'd like to be able to turn off the cooling pad under it. I tried the things outlined in the following:

• https://stackoverflow.com/questions/4702216/controlling-a-usb-power-supply-on-off-with-linux

however this doesn't work anymore in Linux 3.0.0. I read the kernel docs:

• http://www.mjmwired.net/kernel/Documentation/usb/power-management.txt

and tried this (also outlined here - http://www.thinkwiki.org/wiki/How_to_reduce_power_consumption):

for i in /sys/bus/usb/devices/*/power/autosuspend; do echo 1|sudo tee $i; done 
for i in /sys/bus/usb/devices/*/power/level; do echo auto|sudo tee $i; done

I can confirm this works properly for some devices - e.g. my USB keyboard auto-suspends as expected. However, some devices do not - e.g. my USB touchpad, USB hub it's connected to and the cooler are left with power.

My questions:

• Why are devices behaving differently? Does this mean that it's up to each of the devices to decide whether to suspend?
• Is there a way to determine whether a device will go into suspend mode?
• Finally, is there a way to force a device to power down?