send message to user's GUI through command line

[Synoc]

presently I am running Ubuntu 10.04 on multiple old PCs in my house. if it were just MY PCs I would be fine, however, the problem comes in when I have to factor in people who are Windows all the way and can't figure out Update Manager. So to avoid the headaches I am remoting into their computers via ssh, if there is a kernel update that requires a restart I normally just restart their computer for them as well. However before i do that I run "who" to see if they are on. If they are I cannot restart their computer.

I would LIKE to be able to, from the command line, send a message to their GUI informing them they will need to restart their computer after they have concluded their business for the time being. Is this possible? so we are clear, I have my own account with sudoer permissions to administrate this account. I would be sending the message from my account (on the CLI) to their account (preferably a popup window in their GUI).

[matt_symes]

Hi

I have read, but never tried, that samba can do this for you.

echo "Going for reboot now" | smbclient -M <cmputer_name>

Now this i do know for sure: You can get the computer names using

nbtscan 192.168.0.0/24

This will scan the class C subnet 192.168.0.0/24 and you will have to change as appropriate for your network.

It's in the package...

matthew-S206:/home/matthew % apt-cache search nbtscan
nbtscan - A program for scanning networks for NetBIOS name information
matthew-S206:/home/matthew %

You can get extra information using

nmblookup -A 192.168.0.104

Tell us how it goes.

EDIT:

Did i misunderstand you ? Are they on Windows or Linux machines, as the above solution if for sending messages to Windows machines from a Linux box.

If your ssh'ing into a linux box to reboot it then something like this should work (assuming you have notify-send)

DISPLAY=:0.0 notify-send "REBOOTING IN 5 MINUTES" "Your PC will be rebooted in 5 Minutes. Please save all your files"

Kind regards

[Synoc]

trying the notify send worked fine on my computer, however when I ssh'd into the other computer and tried (had to install the program first) I got this message

DISPLAY=:0.0 notify-send "Your Operating system has been updated. when you have finish with your business, please restart the computer. Thank you."
libnotify-Message: Unable to get session bus: /bin/dbus-launch terminated abnormally with the following error: No protocol specified
Autolaunch error: X11 initialization failed.




** (notify-send:5797): CRITICAL **: dbus_g_proxy_connect_signal: assertion `DBUS_IS_G_PROXY (proxy)' failed


** (notify-send:5797): CRITICAL **: dbus_g_proxy_connect_signal: assertion `DBUS_IS_G_PROXY (proxy)' failed


** (notify-send:5797): CRITICAL **: dbus_g_proxy_call: assertion `DBUS_IS_G_PROXY (proxy)' failed
libnotify-Message: Unable to get session bus: /bin/dbus-launch terminated abnormally with the following error: No protocol specified
Autolaunch error: X11 initialization failed.




** (notify-send:5797): CRITICAL **: dbus_g_proxy_disconnect_signal: assertion `DBUS_IS_G_PROXY (proxy)' failed


** (notify-send:5797): CRITICAL **: dbus_g_proxy_disconnect_signal: assertion `DBUS_IS_G_PROXY (proxy)' failed

thank you for your help thus far

[matt_symes]

Hi

Are you logging in as the same user as the user who is logged on ?

I assume this is a session dbus error but i may be wrong.

Kind regards

[Synoc]

no, my own account.

[steeldriver]

I'm not able to recreate your exact error, but I'd expect you'd either need to grab the remote user's DBUS_SESSION_BUS_ADDRESS or at least their Xauthority - the old school way would probably be to have the remote user open up their session authority using 'xhost +', however I think it's recommended to avoid that if possible

FWIW this works for me (it assumes your ssh user can read the remote user's $HOME/.Xauthority using sudo):

steeldriver@htpc-01:~$ xauth list    # we are logged in via ssh and don't have any valid Xauthority cookies 
steeldriver@htpc-01:~$
steeldriver@htpc-01:~$ sudo cat /home/remote-user/.Xauthority | xauth merge -
steeldriver@htpc-01:~$ xauth list    # now we should have a cookie for the active remote display
htpc-01/unix:0  MIT-MAGIC-COOKIE-1  c7eb54429f6b730cd89eea184c352bfc
steeldriver@htpc-01:~$
steeldriver@htpc-01:~$ DISPLAY=:0 notify-send test 'This is a test'
steeldriver@htpc-01:~$

It's probably not strictly necessary, but you can revoke the grabbed Xauthority after with

steeldriver@htpc-01:~$ xauth remove htpc-01/unix:0

[matt_symes]

Hi

no, my own account.

That'll be a problem then.

You'll certainly want a X server cookie so follow steeldriver's post to get the users X cookie.

Post back on how you get on.

the old school way would probably be to have the remote user open up their session authority using 'xhost +', however I think it's recommended to avoid that if possible

I believe it's classed as a security risk.

Kind regards

[Synoc]

steel's tutorial fails at the

sudo cat /home/remoteuser/.Xauthority \ xauth merge -

there is no .Xauthority in the user's home directory

[steeldriver]

My apologies, I just checked and that command doesn't work if the ssh user doesn't have an existing .Xauthority file to merge the remote session's cookie into

You can either create an empty ~/.Xauthority (mode should be 600 i.e. -rw-------) or try this which I *think* will create the file if it doesn't already exist

sudo cat /home/remote-user/.Xauthority | xauth -f ~/.Xauthority merge -

[Synoc]

sudo cat /home/<remote-user>/.Xauthority | xauth -f ~/.Xauthority merge -
xauth:  creating new authority file /home/me/.Xauthority
cat: /home/<remote-user>/.Xauthority: No such file or directory
xauth: (argv):1:  unable to read any entries from file "(stdin)"

no joy

what account should own the .Xauthority file?