As you know, it is hard to get old versions of OS X from Apple. I haven't tried but others say they've had problems.
That is not quite correct. You can get every old Major version you have purchased, like 10.7.x, even after you have purchased and installed a later version like 10.8.x. But what you will get will be the minor version that is current. (Example: Running 10.7.2, you decide to re-download 10.7. When your Mac wakes up, it will be running 10.7.5 -- the Major version you asked for, updated to the latest minor version available.
The only way I can get Screen Sharing to work on the MacBook is if I turn off the Firewall on the iMac.
If turning off the Firewall on an individual computer allows it to operate the way you would like, the FireWall is the problem.
The solution is to do one of:
• Turn off all the FireWalls on all your individual Macs, unless they are port-forwarded from your Router direct from the Internet. In normal use, Your Router's DHCP makes your individual Macs invisible form the Internet -- and no one can reach you except through the Router, which has a really good FireWall already.
• Research what ports are used for Remote Desktop Client and/or Screen Sharing and explicitly open those ports on the Firewall on the individual computers.
Interesting ... I had an enjoyable online chat at the AppStore about this issue and was told to contact Customer Service for a mailed disc. I figured it out that I could in fact download Lion from Option>Purchases>Download . . . it showed up 30 minutes later with an install window. It did download into the Applications folder, but I cannot move it, or burn it, to a disc so it is pretty useless if I need to reinstall . . . can't access it :-(. I'll try the Recovery HD approach and see if it will download the OS from the internet . . . I'm not smart enough to figure out how to reinstall a download that goes into my applications folder but can't be moved, or how to access it for a reinstall . . . hmmmm. Thanks for the help. Rod
Versions up through 10.6 are available on DVD. Anything later is a download, although some are bought through the Apple Online Store.
Once you buy it, a record that you purchased that Major version stays on the Purchases page at the Mac App store, and can be downloaded as often as needed.
As it is downloading, the incomplete download is stored in the protected Applications folder. When it is complete, "Install Mac OS X" launches automatically.
IF you cancel it before the Installation is underway, you can make a Thumb Drive or a DVD copy to use later. This will save the Exact minor version you just downloaded.
IF you allow it to Install, it erases itself just before declaring "Installation Complete!" (you may download it again whenever you wish, but you will get the current minor version.)
Retreating to Recovery_HD is not necessary if you have a working Mac OS X installed. It is much more straightforward to go to the App Store, Purchases page, find it and click Download.
Thanks Grant. #1 the Firewall: Here's my set up. I have a Comcast modem as my IP that connects by ethernet cable to AirPort Express. It provides the WiFi to my iMac and MacBook and assigns iPv4 addresses as 10.0.1 . . . For WiFi security I use WPA2 Personal. Is that adequate Firewall protection that would allow me to turn off the Firewall on the iMac? #2 the Download: I was able to download "Install Mac OS X" into the Application Folder on both the iMac and MacBook. It automatically prompted me to continue the install, but I did not. I will only install on the MacBook where I seem to have the Screen Sharing problem. When I attempted to make a DVD copy, there was not enough space (requires 4.7 GB, my DVD capacity is 4.5). Not a problem because it is unlikely I'll ever use it again and, if so, repeat the process as you outlined. Are you saying I can simply do the install without Recovery_HD and my files will be safe? Thanks for our attention and help!
Is that [MY Router providing DHCP] adequate Firewall protection that would allow me to turn off the Firewall on the iMac?
Yes. Your Router provides DHCP Addresses in one of three ranges that are not Routable on the Internet. They are local, "strictly private" ranges of Addresses. They cannot be reached directly from the Internet. They are also not unique -- millions of computers behind Routers have those same 10.0.1.xxx Addreses assigned (without issue).
When you have stuff that is going to the Internet, the Router acts as your Agent, and uses its OWN Address as the "respond-to" Address for your requests. If incoming traffic appears to be a bona fide response to a query, your Router looks up the local Address of your Mac and inserts the local, private Address, then forwards the response packet to your Mac [Network Address Translation, the other half of DHCP].
Unsolicited incoming packets (not in resonse to a query your Mac made) are seen as equivalent to spam and are discarded by your Router.
I will only install on the MacBook where I seem to have the Screen Sharing problem.
From there, it will only install on any locally attached drive, internal or external. It will not reach across your network and install on another Mac.
When I attempted to make a DVD copy, there was not enough space (requires 4.7 GB, my DVD capacity is 4.5).
It requires a Dual-Layer DVD or an EMPTY (or contents-expendable) 8GB USB thumb drive [it writes over everything].
Dual-Layer DVD is not especially exotic, as I think Dual-Layer DVDs have been used for official Installer DVDs since about 10.5. All Mac drives that read DVDs can read Dual layers. Most Mac drives can also write at least one flavor, but check your drive specs carefully as there are several types and several incompatible speed ranges.
Are you saying I can simply do the install without Recovery_HD and my files will be safe?
The tools in Recovery_HD are limited. If you use Recovery_HD to do the download, your Mac is tied up doing nothing else for at least an hour, sometimes much more. If you use the Mac App store in a functioning Mac, you can continue to use your Mac while the software downloads in the background.
Once you start the Installer, it does a restart in short order and takes over your Mac so you can't do anything else while the actual Install is running.
Mac OS X software Install (regardless of how the Installer software was downloaded) is designed to be as fail-safe as possible. It does not intentionally modify any files beyond the ones that are part of Mac OS X. Files are written to the Drive, and then when everything seems to be ready, the new files are moved into place to be ready for the next Restart. They are not actually made part of the running System until that Restart. If the Install fails, it is intended to leave your drive completely un-modified.
Third-party Applications and ALL User files are intended to be left alone, HOWEVER...
If you have Hard drive problems, and fail to repair them before starting the Install, there is a possibility of data loss. It is prudent to run Disk Utility (Verify Disk) and check for Directory Errors before you begin.
Mac OS X Applications are intended to never modify themselves, and are stored in the protected Applications folder to enforce that discipline. Any "customization" is handled by User Preferences, which are stored mainly in User directories, except for those so fundamental to the Mac operation that they are stored in a System Library Preference file -- and there are very, very few of those.
It is a real advantage that Install works in this non-intrusive way, but it has a drawback. Sometimes the problems you are experiencing are caused by Preferences and add-ons that are not replaced by Installer.
In this case you need to perform a much more intrusive "Clean-Install" or "Erase-and-Install". You make sure you have adequate Backups (and since you are about to ERASE the boot drive, "Adequate" means at least TWO copies), then ERASE the Boot drive, then Install onto a blank drive. This assure that any problems are caused by Apple-Installed items ONLY, and helps a lot when chasing down odd System problems.
Thank you Grant for your prompt and thorough replies. You explain things very well and give me confidence to proceed. One more question: When you talk about "routers" above, are you referring to the modem from Comcast? or my AirPort Express? or both? For now, I will simply turn off the Firewall on my iMac so I can use Screen Sharing initiated by my MacBook, the way it was before something broke :-(. It's intellectually challenging to figure out what went wrong and how to fix it . . . kind of up your alley :-)! However, I, and a colleague of yours (Ralph) in these forums, have invested enough time trying to isolate the culprit. Sometimes the chase is exciting as the catch. In this instance, I'll settle for the catch :-). Thanks again.
When you talk about "routers" above, are you referring to the modem from Comcast? or my AirPort Express? or both?
Comcast is typically supplying a modem (without Router capability) or an odd device that is essentially a ONE-port Router/Modem combination. [it may also be the modem for your cable-TV.] The one "computer" that you hook up to it is your AirPort base station, possibly using DHCP again on the port facing the comcast modem. The modem then supplies the "only" DHCP Address it can for the Router to use, and you are in business.
The Airport Base Station will then supply typically up to 50 DHCP Addresses from a different set for all the real computers on your local network. (An Express may have a lower limit, I am not familiar with those details.)
You can have multiple AirPort and/or Brand-X Base stations providing WiFi signal and connection for your local network. They can interlock closely or be fairly separate. But for a well-behaved Network, only ONE of those Base Stations should issue the local IP Addresses for computers via DHCP -- all others should be set up only as WiFi Access points (i.e., with DHCP turned off).
I am the person referred to in the first post.
My email is in my profile and some people use it contact me.
I am running Mavericks at my end and Rod and I have been text chatting and Screen Sharing in iChat/Mavericks.
As you know later versions of the OS come with the Apple Remote Desktop client end installed along with the OS.
This "engine" works for Apple Remote Desktop, the Finder Screen Sharing option (Finder > Go Menu > Go to Server > VNC://xxx.xxx.xx.x) and the iChat (or higher) Screen Sharing.
Rod has three computers that he is using to Screen Share using the alternative Network Window > "server" Highlight and then the Screen Share Button which invokes the Screen Sharing app.
I could share my Mavericks/iMac screen with Rod but I was only seeing a white screen from Rod's Macbook.
As it was in iChat/Messages we could still talk to each other.
I could actually Screen Share in iChat/Messages to Rod and VNC:// share to my Snow Leopard computer at the same time and show Rod the Desktop and Browser on the Snow Leopard computer.
We spent some time on Saturday on this and again on Sunday which was Text Chatting and sending pics.
At present Rod is not trying to use the app over the internet (which would require Port Forwarding or the Airport's equivelant).
He is just trying to get all three computers doing the same thing in both directions.
I am using Little Snitch at my end and from the Alerts I get I can tell Rod's Modem is not routing and the Airport devices is the one doing the Login to the ISP. (iChat/Messages shows the Public IP and the LAN IP in Error Messages as well)
During the Screen Sharing we did on Saturday I did also see his Airport's settings.
In his Macbook's Firewall he is showing that the Screen Sharing (pulled from the System Preferences > Sharing Pane) is allowed via the items above the line in the list in the Firewall.
However further down the list is the screensharingd, the daemon that deals with this. At times it is showing that it is turned Off, despite specifically changing it.
Rod is also looking in the System Profiler and seeing the items listed in the Firewall and the Firewall can report it "On" but the list reports it as Blocked.
We did not try a Screen Share of his screen with the Firewall Off.
My feeling is that .plist somewhere that contains the info for the Firewall settings is no longer Writable by Rod.
I can't seem to find the responsible item on my computer to suggest if Rod removes it on his end or checks that he has Ownership and Read and Write Permission.
We started by discussing using the Combo version of the last update he did to possible provide a "correction" that it can do in some cases.
We then also talked about doing a reinstall as a way of shortening the process and realistically a cleaner way of doing things.
Of course the other possible is that the actual Apple Remote Desktop engine is the item with a flaw and that an reinstall would be the way to go anyway.
It was while we were texting on Sunday that Rod download the reinstaller item on his iMac when he would need it on his Macbook.
It was at this point that I went Off line my time yesterday.
iMac 2.5Ghz 5i 2011 (Mavericks 10.9)
G4/1GhzDual MDD (Leopard 10.5.8)
MacBookPro 2Gb (Snow Leopard 10.6.8)
Mac OS X (10.6.8),
Couple of iPhones and an iPad
With the indivdual Mac firewalls off, The FireWall and DHCP in your Router will keep you safe from arbitrary and capricious attacks from the Internet.
That will NOT provide you with anything resembling complete safety from all Malware on the Internet. But this very approachable set of short articles by contributor Thomas Reed will go far to provide the background needed for self-defense: