Ubuntu – How to restrict the kids’ computing time

bashparental-controlssoftware-recommendation

Access to our computer (not only to the internet) needs to be restricted for the accounts of my kids (7, 8) until they are old enough to manage this by themselves. Until then we need to be able to define the following:

  • the hours of the day when computing is o.k. (e.g. 5 – 9 pm)
  • the days of the week when computing is not o.k. (e.g. mondays to fridays)
  • the amount of time allowed per day (e.g. 2 hours)

In 11.10 all of the following that used to do the job don't work any more:

  • Timekpr: for > 11.10 no more available through the ppa.
  • Timeoutd: command line alternative, but from 11.10 removed from the repositories.
  • Gnome Nanny: Looks great but repeatedly crashes to force restarting X-server. So we can't use or recommed this program at the moment.

Are there any other alternatives?

Best Answer

  • Lock Screen Timer

    systray.gif

    Create your own Screen Lock Timer instead of 3rd Party applications

    Although there are 3rd Party applications to do this, you can create your own. Summary of steps:

    • Use gedit to create script lock-screen-timer
    • Copy and paste code from this window to lock-screen-timer
    • Mark lock-screen-timer as an executable
    • Test it!
    • Configure Nautilus to execute bash scripts
    • Create desktop shortcut link
    • Monitor time remaining

    Use gedit to create script lock-screen-timer

    Open the Terminal using Ctrl+Alt+T and type:

    gedit lock-screen-timer
    

    Copy and paste code from window below to lock-screen-timer

    Toggle back to this screen and copy the following code by highlighting it and pressing Ctrl+C:

    #!/bin/bash
    
    # NAME: lock-screen-timer
    # PATH: $HOME/bin
    # DESC: Lock screen in x minutes
    # CALL: Place on Desktop or call from Terminal with "lock-screen-timer 99"
    # DATE: Created Nov 19, 2016. Last revision Mar 22, 2018.
    # UPDT: Updated to support WSL (Windows Subsystem for Linux)
    #       Remove hotplugtv. Replace ogg with paplay.
    
    # NOTE: Time defaults to 30 minutes.
    #       If previous version is sleeping it is killed.
    #       Zenity is used to pop up entry box to get number of minutes.
    #       If zenity is closed with X or Cancel, no screen lock timer is launched.
    #       Pending lock warning displayed on-screen at set intervals.
    #       Write time remaining to ~/.lock-screen-timer-remaining
    
    MINUTES="$1" # Optional parameter 1 when invoked from terminal.
    
    # if no parameters set default MINUTES to 30
    if [ $# == 0 ]; then
        MINUTES=30
    fi
    
    DEFAULT="$MINUTES" # When looping, minutes count down to zero. Save deafult for subsequent timers.
    
    # Check if lock screen timer already running
    pID=$(pgrep -f "${0##*/}") # All PIDs matching lock-screen-timer name
    PREVIOUS=$(echo "$pID" | grep -v ^"$$") # Strip out this running copy ($$$)
    if [ "$PREVIOUS" != "" ]; then
        kill "$PREVIOUS"
        rm ~/.lock-screen-timer-remaining
        zenity --info --title="Lock screen timer already running" --text="Previous lock screen timer has been terminated."
    fi
    
    # Running under WSL (Windows Subsystem for Linux)?
    if cat /proc/version | grep Microsoft; then
        WSL_running=true
    else
        WSL_running=false
    fi
    
    
    while true ; do # loop until cancel
    
        # Get number of minutes until lock from user
        MINUTES=$(zenity --entry --title="Lock screen timer" --text="Set number of minutes until lock" --entry-text="$DEFAULT")
    
        RESULT=$? # Zenity return code
        if [ $RESULT != 0 ]; then
            break ; # break out of timer lock screen loop and end this script.
        fi
    
        DEFAULT="$MINUTES" # Save deafult for subsequent timers.
        if [[ $MINUTES == 0 ]] || [[ $MINUTES == "" ]]; then
            break ; # zero minutes considered cancel.
        fi
    
        # Loop for X minutes, testing each minute for alert message.
        (( ++MINUTES )) 
        while (( --MINUTES > 0 )); do
            case $MINUTES in 1|2|3|5|10|15|30|45|60|120|480|960|1920)
                notify-send --urgency=critical --icon=/usr/share/icons/gnome/256x256/status/appointment-soon.png "Locking screen in ""$MINUTES"" minute(s)." ;
                if [[ $WSL_running == true ]]; then  
                    powershell.exe -c '(New-Object Media.SoundPlayer "C:\Windows\Media\notify.wav").PlaySync();'
                else
                   paplay /usr/share/sounds/freedesktop/stereo/complete.oga ;
                fi
               ;;
            esac;
    
            # Record number of minutes remaining to file other processes can read.
            echo "$MINUTES Minutes" > ~/.lock-screen-timer-remaining
    
            sleep 60
    
        done
    
        rm ~/.lock-screen-timer-remaining # Remove work file others can see our progress with
    
        if [[ $WSL_running == true ]]; then  
            # Call lock screen for Windows 10
            rundll32.exe user32.dll,LockWorkStation
        else
            # Call screen saver lock for Ubuntu versions > 14.04.
            dbus-send --type=method_call --dest=org.gnome.ScreenSaver /org/gnome/ScreenSaver org.gnome.ScreenSaver.Lock
        fi
    
    done # End of while loop getting minutes to next lock screen
    
    exit 0 # Closed dialog box or "Cancel" selected.
    

    Then toggle back to the empty gedit window and paste the code using Ctrl+V. Save the file and exit the editor back to the command prompt.

    Mark lock-screen-timer as an executable

    Now we need to make the script executable by typing:

    chmod +x lock-screen-timer
    

    Test It!

    Before calling the script from the GUI, we'll call it from the terminal so we can see if any error messages are displayed:

    ~/lock-screen-timer
    

    You are prompted for the number of minutes:

    Lock Screen Timer

    Set the desired number of minutes and click OK to start the timer. When there are 15, 10, 5, 3, 2 and 1 minute(s) left a system sound is heard and a message bubble appears advising when the screen will be locked. After the screen is locked you need to enter your password to unlock the screen.

    Configure Nautilus to execute bash scripts

    Nautilus defines what happens when we double click on an executable script when it's the files display window or a link on on the desktop. Normal behavior is to edit the script using gedit. We want to change this behavior such that it is executed.

    Start Nautilus and navigate to directory containing lock-screen-timer. Left click on it once to give it focus. Hover mouse over top menu bar until "File Edit..." menu appears, use:

    1. Click Edit drop-down menu
    2. Click Properties option
    3. Click Behavior tab
    4. Observe the radio option buttons under Executable Text Files
    5. Check radio button Run executable text files when they are opened

    Create desktop shortcut link

    From previous section lock-screen-timer still has focus. If not, navigate to the script and left click on it once to give it focus. Then use:

    • Right click on the file and the context-menu options appear.
    • From the menu select Make Link.
    • A new icon appears called Link to lock-screen-timer.
    • Left click on the new icon and drag it from Nautilus to your desktop.

    Now you can double click on the desktop shortcut link and the script is run. A dialog box appears to get the number minutes. Two buttons are presented Cancel and OK. If you click the X to close the window it is the same as selecting Cancel.

    After the timer is running and you double click on it again the first running copy is "killed". You can now start a new scren lock countdown or click Cancel for no countdown.

    Display Time Remaining in systray / notification area

    While lock screen timer is running it records how many minutes are remaining into the file ~/.lock-screen-timer-remaining. You can look at this file with the watch command or display it on Ubuntu's system tray / application indicator bar as shown at the top of this answer. To display time remaining in the notification area, follow the instructions in this Q&A: (Can BASH display in systray as application indicator?).