Cannot mount writable partitions on HD and flashdrive

[rybrns]

I've searched for this problem but can't find anything that matches this problem, so sorry if this has been answered before.

I've used Unix in the past, but not for a few years, so I'm really a newbie once again. Trying to rescue data from a drive that won't boot into Windows xp using the Knoppix CD, I see the damaged windows partition has been mounted and I can read its data. If I connect a second HD or a usb flash drive, these also appear on the desktop. The problem is making them writable partitions. I can copy files to a floppy disk but not to the another HD or flash drive.

I set the permissions on the partitions to r/w/x, removed the write-protect checkmark in the file system property screens, and set the owner to user, but the os still tells me I don't have write permission. How do you make a partition writable (if that's the real problem here)?

Can anyone point me in the right direction?

[Harry Kuhman]

Answer #6

[rybrns]

Thanks. That was the answer I couldn't find.

*RANT MODE ON* I had assumed that Knoppix used Unix conventions, and that making a volume's user/group/world permissions r-w-x enabled, that would in fact make the volume writable. These permissions are in the volume's Properties | Permissions, where they logically should be. I even made sure that I had the proper "Group" permissions to write to the volume! Apparently changing these permissions and ensuring the proper group membership does nothing, which "violates" a Unix principle. Why on earth is there a separate section, "Actions," where this is done? So is Knoppix Unix, or an attempt to copy Windows, using Windows' non-intuitive and confusing interface? Oh, for the ability to use "grep" in Windows! *RANT MODE OFF*

Again, thanks for the help.

[Harry Kuhman]

See man mount. Are you under the impression that mount should not be allowed to mount a device as read only if the user chooses to do so and it must be read-write if the user has rights to the files? That would be rather foolish, as there are many good reasons that a user might want to mount a partition as read-only. That is what is happening here, because of the target user for Knoppix, Klaus has elected to default mounts of Microsoft partitions to read only, so that the novice just getting his first look at Linux with the Live CD does no harm. It is easy enough to change the access but it has to be done deliberately.

[rybrns]

"Are you under the impression that mount should not be allowed to mount a device as read only if the user chooses to do so and it must be read-write if the user has rights to the files?"

No, not at all. I thought that there were two steps to being able to write to a partition: mounting it first, and then making it writable. My error was assuming that by changing the volume's r-w-x permissions to, for example, 777, would make the volume writable for all users. That was certainly a deliberate step. I didn't think of how the existence of the Windows partition would entail yet another level of permission: permission to write to a mounted Windows drive.

Sure, I agree that safety dictates that such partitions should initially be write-disabled. My only annoyance (since I had to look for help and that took time) was that it wasn't at all apparent that simply changing the standard Unix access permissions wouldn't work. I think the message I saw was something like: "You need permission to ... drop files in this folder." Naturally, I looked for where one could change a volume's permissions. "Properties" seemed logical. And indeed, there was a tab marked "Permissions." When is write permission not permission to write?

Of course there are good reasons to protect Windows partitions. The disaster that would result from writing to an NTFS partition is one example. But possibly the error message could be better worded. "You need to enable writing to this partition...."

[Harry Kuhman]

... My only annoyance (since I had to look for help and that took time) was that it wasn't at all apparent that simply changing the standard Unix access permissions wouldn't work. I think the message I saw was something like: "You need permission to ... drop files in this folder.".......... But possibly the error message could be better worded. "You need to enable writing to this partition...."

What is happening here is that you are seeing error messages from the OS (Linux) or even the applications. But Knoppix is a Live CD Linux distro, based on Debian and using the standard Linux kernel and applications. Knoppix in no way hides this nature of the distro, it is very well documented and if you read minimal information on Knoppix then you should come across it. It would not be reasonable (or in many people's view desirable) for Knoppix to modify the kernel or the applications to change these error messages.