I'm trying to block some websites via /etc/hosts  
I can't seem to figure out how to run the LaunchAgent with the correct permissions.  
  
    $ ls -la ~/Library/LaunchAgents/hosts_Blocksites_AM.plist     
    -rw-r--r--@ 1 root  staff  1854 Aug 25 11:55 /Users/bryanwheelock/Library/LaunchAgents/hosts_Blocksites_AM.plist    
  
I set a UserName key:  
  
	<key>UserName</key>  
	<string>root</string>  
  
  
Here is the hosts_Blocksites_AM.plist:    
  
    <?xml version="1.0" encoding="UTF-8"?>  
    <!DOCTYPE plist PUBLIC "-//Apple//DTD PLIST 1.0//EN" "http://www.apple.com/DTDs/PropertyList-1.0.dtd">  
    <plist version="1.0">  
    <dict>  
    	<key>Label</key>  
    	<string>local.job</string>  
    	<key>ProgramArguments</key>  
    	<array>  
    		<string>cp</string>  
    		<string>/etc/hosts_BLOCKED_sites.txt</string>  
    		<string>/etc/hosts</string>  
    	</array>  
    	<key>RunAtLoad</key>  
    	<true/>  
    	<key>UserName</key>  
    	<string>root</string>  
    	<key>StartCalendarInterval</key>  
    	<array>  
    		<dict>  
    			<key>Hour</key>  
    			<integer>8</integer>  
    			<key>Minute</key>  
    			<integer>15</integer>  
    			<key>Weekday</key>  
    			<integer>1</integer>  
    		</dict>  
    		<dict>  
    			<key>Hour</key>  
    			<integer>8</integer>  
    			<key>Minute</key>  
    			<integer>15</integer>  
    			<key>Weekday</key>  
    			<integer>2</integer>  
    		</dict>  
    		<dict>  
    			<key>Hour</key>  
    			<integer>8</integer>  
    			<key>Minute</key>  
    			<integer>15</integer>  
    			<key>Weekday</key>  
    			<integer>3</integer>  
    		</dict>  
    		<dict>  
    			<key>Hour</key>  
    			<integer>8</integer>  
    			<key>Minute</key>  
    			<integer>15</integer>  
    			<key>Weekday</key>  
    			<integer>4</integer>  
    		</dict>  
    		<dict>  
    			<key>Hour</key>  
    			<integer>8</integer>  
    			<key>Minute</key>  
    			<integer>15</integer>  
    			<key>Weekday</key>  
    			<integer>5</integer>  
    		</dict>  
    	</array>  
    	<key>StandardErrorPath</key>                                                                                                                                                          
    	<string>/tmp/mycommand.err</string>                                                                                                                                       
    	<key>StandardOutPath</key>                                                                                                                                                                <string>/tmp/mycommand.out</string>  
    </dict>  
    </plist>  
  
Here are the errors:    

    $ cat /tmp/mycommand.err   
    sudo: no tty present and no askpass program specified  
    cp: /etc/hosts: Permission denied  
  
  
I had tried to add the sudo command to the program arguments, but I don't think that was correct. 

EDITED:

Changed Label key:  

	<key>Label</key>  
	<string>local.hosts.blockingAM</string>  

Removed UserName key.

Moved the plist and changed name:  

    $ ls -la /Library/LaunchDaemons/
    -rw-r--r--@  1 root  wheel  1474 Aug 29 13:19 local.hosts.blockingAM.plist  

I was still getting permission errors until I ran launchctl with sudo:  

    sudo launchctl load /Library/LaunchDaemons/local.hosts.blocking.plist