Is this combo update ok to install?

[EmilyQ]

I recently got a Mac and my friend downloaded Mac OS X v10.6.3 v1.1 for me and put it on a disc so I could install it. I do have some concerns however.

First, Apple lists the size on their website as 785.29 MB. The file when placed on the hard drive is listed as 823.4 MB, and I believe 823.5 MB if I right click on the disc. Both of those seem to be a big difference than 785.29 MB. Is this a legit file? How can I tell?

Secondly, while my friend also has a Mac I'm sorry to say they don't keep their computer as safe as they should. He doesn't install updates and I think could have that trojan that comes in pirated iworks or ilife, since he didn't buy the program. Would my combo update be infected be infected with a trojan horse or key logger or virus?

 

[forcefieldkid]

Are you running 10.6 now? If you recently got a Mac I'd assume so.. why dont you just run a proper software update?

 

[EmilyQ]

Are you running 10.6 now? If you recently got a Mac I'd assume so.. why dont you just run a proper software update?

No, it's 10.6.1. And I'm on my windows computer. I also didn't run software update because that will take a loooong time to download.

 

[forcefieldkid]

Sorry, saw your edit. Long time to download or not, its the safer way and you should really do that.

 

[EmilyQ]

If I went to a computer tech shop and asked them to download the update for me do you think I could trust the file to be safe?

 

[UngratefulNinja]

Something is not right here.

 

[forcefieldkid]

This better be some kind of 2 day download for you to go to all this trouble to avoid it!

 

[EmilyQ]

Well my connection is slow and has also kind of been on the fritz lately.

 

[forcefieldkid]

Then just wait? What's the rush?

 

[EmilyQ]

Then just wait? What's the rush?

I'm impatient *wink*

 

[forcefieldkid]

Something is not right here.

Agreed.

 

[EmilyQ]

All right, I'll wait. Thanks...

 

[chown33]

... Is this a legit file? How can I tell? ...

Here's how you tell. It's somewhat technical, in that you have to enter commands into Terminal.app. But if you can follow instructions, it's not a big deal.

Every update distributed by Apple has a "hash" or "digest" published on the download page. This is essentially a checksum to confirm that what you have is exactly what Apple published.

http://support.apple.com/kb/DL1017

Visit the above webpage and find the word "SHA" at the bottom of the article. The value is given as 39d16279373906041a066f409b5f667e2bca77e2. Don't just trust me, go see for yourself. This is very much to the point: you should be able to confirm the correct values for yourself.

Now, after you've downloaded the update, or obtained it by other means, you have to confirm that the SHA hash for the file you now have is identical to the SHA hash value published by Apple. That's where the Terminal commands come in.

Copy and paste the following into Terminal, but DON'T HIT RETURN:

openssl sha1

Make sure there's a space after sha1.

If you do hit return, then press control-C and try again.

Now, switch to Finder and open whatever folder contains the OS update file. Drag the file onto the Terminal window and drop it. Terminal.app should insert a pathname so you have a line that looks like:

openssl sha1 /Volumes/ExampleDisk/ExampleFolder/MacOSXUpdCombo10.6.3v1.1.dmg

where ExampleDisk is the name of the disk, and ExampleFolder is the name of the folder on that disk where the update is stored.

Switch back to Terminal and hit RETURN or ENTER. It will take some time for it to calculate the hash. If you launch Activity Monitor.app (in Utilities), you should see significant CPU usage.

When the command completes, it will print out something like this:

SHA1(/Volumes/ExampleDisk/ExampleFolder/OS/10-6-3/MacOSXUpdCombo10.6.3v1.1.dmg)= 39d16279373906041a066f409b5f667e2bca77e2

The important part is after the = sign.

If the printed value is not exactly the same as Apple's published value, then there is some difference between the official published update and the file you have. There's no way to identify what the difference is without more work, but you don't need to know that anyway. All you need to know is whether what you have is the same as what Apple published.

By the way, I have the 1.1 combo update, and its size is 823.4 MB when Snow Leopard shows it, but 785.3 MB when 10.5 Leopard shows it. This is simply the difference between base 10 (1000) and base 2 (1024) counting. All Apple downloads show the base 2 size, not the base 10 size.