iMac reset (ethernet) network connection

grumpycrab

Hi, anybody know how to reset an (ethernet) connection on an iMAc without rebooting it?
(Our neighbour is having broadband problems and when I plugin my router it defaults to 10.0.0.X network -rather than normal 192.168... and the imac just locks up).

almillar

You can't disable, renable the hardware like you do in Windows, but if it's using DHCP, then:
System Preferences, networking. Ethernet down left hand side, advanced button bottom left. TCP/IP tab along the top should give you all that info including your dodgy IP address. 'Renew DHCP lease' will make the Mac try to get an IP address again.
This is all after you've restarted the router of course, as the easy thing to do?!

grumpycrab

Thanks - will try that. The iMAc programs just lock-up which I'm surprised at. I have to force-quit them and if "restart" doesn't work have to hold the power button for a period to switch off.

almillar

This doesn't sound good to be honest but let us know what happens. Could be faulty hardware somewhere, and being an iMac could mean a whole new board.
First thing to do is make sure there's a backup of everything as you could already be on borrowed time...

grumpycrab

You've got me worried now. Symptoms are:- (having never played with an imac) on ethernet connection
1. apps lock up; e.g. click on Safari, Email, System Prefs and the icon (on bottom row of the screen) moves up and down (is it trying to start?) and have to force quit them
2. cannot restart or logout (because one or more apps are not in a good state)?
3. I CAN run the Network Utility and netstat, ping all seem ok, so its not a connectivity issue (perhaps) as I originally thought; I have changed the connection from ethernet to wifi to see if there's any change

After a reboot things look ok. I'm not sure how long after that things go pear-shaped.

Picture here of me trying to do a shutdown.


And attempting a shutdown after I've killed all apps I can.

What's a good log to look at? Cheers.

UPDATE:
1. POST is successful - no errors recorded
2. the only app that seems runnable when the majority are "stuck" is Network Utility. Is this a clue?
3. trying a different wireless connection with mail closed and Safari running with masterchef playing...

almillar

Make a backup BEFORE any further diagnostics.
Done?
Don't lie to me!!
Now that you've backed up...
I've no idea what logs to look at. Have a Google to find out how to check the SMART status of the hard drive. Onyx is a big massive utility that does loads of stuff, including this, but may be overkill.
If that all checks out OK, then work the drive a bit harder. Goto Apps, Utilities, Disk Utility. Select the Macintosh HD (or whatever the system HD has been named) and find in amongst everything 'Repair disk permissions'. Let it run through that. The more errors it finds, the more likely it is that that was the problem. You want a huge list to scroll through!
I think you can still access the RAM on all iMacs, might be worth reseating (take it out, put it back in) the RAM in case it was loose or there was a static build up or anything.
If all that is done and things don't improve, I'd be doing a fresh install of OSX (I don't see what version you're using). Let me know how the above goes and I can let you know about installation or whatever, that's me out of ideas for FREE fixes for the moment...

Mr_Toad

Have a look at the log files. See if you can find anything to give you a clue but it isn't for the faint hearted!

They are located in /private/var/log directory there are others in /library/logs

You might not be able to see the above in finder as they might be hidden but you can in terminal.

If you'd rather use Finder then you may need to unhide the files. Below is a shell script to do this;

#!/bin/bash
# check if hidden files are visible and store result in a variable

#echo $isVisible

isVisible=$(defaults read com.apple.finder AppleShowAllFiles)
#echo $isVisible
# toggle visibility based on variables value
if
[ $isVisible == "FALSE" ]
then
#echo "Showing"
defaults write com.apple.finder AppleShowAllFiles TRUE
else
#echo "hiding"
defaults write com.apple.finder AppleShowAllFiles FALSE
fi

# force changes by restarting Finder
#echo "killing finder"
killall Finder
exit
osascript -e 'tell application "Terminal"' -e 'close front window' -e 'end tell'
#/bin/sh kill -3 $(ps wax | grep "[T]erminal.app" | awk '{print $1}')
#exit


All of the problems you are describing are very odd and unusual. As almillar suggests I'd be doing a fresh install of the OS then restoring the user folder and files.

Let us know how you get on.

grumpycrab

Thanks (and sorry for using 2 threads for this). As an Apple novice I'm impressed with the support (so far). The 1 hour session was a Tutorial and so it was a bit naughty of us to try and debug our "apps freezing after X hours" issue.
The engineer did a couple of things (reset Safari and Mail preferences and PRAM - although I had to tell him what the keyboard shortcut was to do this!).
Will see if anythings different at home and, if not, book it in for the Genius Bar and tell them it needs a soak test to repeat the problem. Apparently they'll do this free-of-charge.