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2012-10-27, 12:38 #1
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- Feb 2010
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Where to find a comprehensive explanation about permissions or security set
I am trying to copy data from the hard drive of a defective computer that ran Windows XP. The fault was apparently with the memory and not with the hard drives.
I don't have permission to copy the interesting files. I am administrator and according to Windows (in properties of the pertinent folders) have permission to do everything.
Now I could search the net for procedures until I find one that works, but I would like tounderstand how these permissions work, so that next time I have asimilar problem I can solve it myself (since it is unlikely the solution that would work here would work again). So does anyone knowa good source for information to learn how permissions work ? I read think-like-a-computer.com/2011/05/11/windows-access-denied-folder-administrator,but none of the solutions it presents work.
I am really frustrated about Windows 7,so I'll make a short rant here.
Why doesn't Windows help provide a solution to that problem ? If I write a program and I foresee errormessages then I don't have to be a genious to know that if a user gets to see one that he likely wants to do something, but can't. So it makes sense to provide the relevant information to him, like inthe help, but if I type “provide administrator permissions”(error messages vary) I don't get information on how to do that or any explanation that actually works on how to copy those files. Why not ?
2012-10-27, 12:43 #2
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- Jun 2010
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This is a good presentation: http://www.howtogeek.com/72718/how-to-understand-those-confusing-windows-7-fileshare-permissions/
To solve your problem, in a simple and effect way, you can use TakeOwnership, as long as you are using Vista, 7 or 8.
2012-10-30, 05:28 #3
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- Feb 2010
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Thank you for the explanation and thesolution.
My understanding summarized :
A Windows is governed by Sharing andNTFS permissions. A user or group is identified by Windows through anSID. A user or a group can belong to one or more groups. A file orfolder has a list called ACL containing SIDs with with correspondingpermissions/prohibitions (called an ACE). If a sharing permissionallows/prohibits an action and an NTFS permission probits/allows it,then the action is prohibited.
The article is however far fromcomplete :
- There is User Account Control (UAC), which is, explained in the Windows help. It reduces permissions of the user, but also allows for easy acquiring of the required permission by means of a dialog window. Therefore turning off UAC doesn't give you any permissions and so I don't understand why it is sometimes presented as a solution to “Access denied” type of errors.
- In order to do something with a file or folder the proper approach seems to be to make sure you and all the groups you are member of have the required permissions. But apparently only the owner of an object can meddle with permissions. In the NTFS Permissions only the 'Full Control' permission (a 'permission' is a collection of 'special permissions') includes the special permission 'Take Ownership'. What is also interesting is that once you are owner of an object Windows can automatically grant you the permissions required to perform the desired action (via a button of the style 'Continue' on the dialog Window)
- What is the Everyone group ? One can find the local users and groups in 'Computer Management' via right-clicking on 'Computer' or 'My Computer' and choosing 'Manage'.Then choose 'Local Users and Groups' in 'System Tools' (apparently in some Windows 7 systems that feature is missing). But there is noEveryone group listed there. Could it be that Everyone is the group that contains all users and other groups and is not listed to prevent it being changed ? But according to the membership information in 'Computer Management' no one is member of the Everyone group !?
- I ran a virus scan on the trouble some drive with Avast Antivirus, then on a troublesome folder 'kathelijne' of according to Windows 11MB (that is in fact 52GB) to simplify.Avast reported (after the second scan) one file it couldn't scan and provided the path and filename, while I don't even have access to the folder a few levels higher. How can that be?
- Sharing permissions allegedly only apply to access over a network. Does that mean that a guest user hasthe same rights for accessing a FAT32 drive as an administrator ? How come that changing the Sharing permissions sometimes influenced my possibility to access locally ?
- Sometimes the permissions are greyed out (unchangeable), even when I belong to a group that is owner. Whyis that ?
- A user or group with full control is supposed to have read access to the security information. However,about folders I had no access to I was told to I needed to become an owner before I could see that information. (It is only after becoming owner that I saw I had full control.)
- Why does one need to take ownership to copy files ? If one can take ownership, one has already full control, meaning one can read, which should be enough to copy.
Windows 7 has actually more help filesthan the one you get by pressing via 'Help and Support' in the Start menu. I found the link to the help on 'Access Control' in the security tab of the properties of a folder. There is also a 'Disk Management' help with useful information that one can open via 'Computer Management'.
Finally I managed to copy the files this way. Since I was administrator I had full control of the folder,so I changed ownership. There is a checkbox to make the ownership also apply to subfolders and files. However, there were about 10 objects for which that didn't work (“Access is denied”) and that were therefore skipped and Windows gave insufficient information to identify the files. I then changed the permissions of Everyone in the Sharing tab to write when it was only read. I tried to take ownership of folders and its contents again and now I had errors only for 2 files. I did it a third time and got again 2 errors. Then a 4th time of a containing folder (thus that included the folder I just tried) and now there was only 1 error.
After having tried to take ownership of all the folders of the disk I set to copying them. I had earlier already told Windows to copy the whole disk, but then who the copy was for noticed that most was missing. Copying the non-system disk of the computer worked without any significant hassle. Here I had to meddle with the security settings and now the copying required a lot of interaction with dialog boxes. My computer spent most of the night waiting for me to click 'Continue'. After all was supposedly copied(except for the files I had resigned myself to abandon) I checked to find out that of the 76 GB Windows had only copied 43GB! So I had to go through the drive finding what Windows had forgotten to copy and telling Windows specifically to copy it.
How is one supposed to copy a system hard drive ?