bug#14383: cp --one-file-system / will not copy whole root filesystem
Hi! On systems like linux, cp / -a --one-file-system (destination) will not copy whole root filesystem. It is not cp's fault, but the behaviour is quite surprising to the users, so maybe it would be worth warning in man page? Something like -x, --one-file-system stay on this file system Note that on systems that allow mounts over non-empty directories (like Linux), cp / -ax (destination) will not copy whole filesystem. In particular, content of /dev will not be usually copied, because distributions mount tmpfs over /dev. [Ok, there's hopefully better wording...?] Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
bug#14383: cp --one-file-system / will not copy whole root filesystem
severity 14383 wishlist thanks Pavel Machek wrote: On systems like linux, cp / -a --one-file-system (destination) will not copy whole root filesystem. It is not cp's fault, but the behaviour is quite surprising to the users, so maybe it would be worth warning in man page? Something like -x, --one-file-system stay on this file system Note that on systems that allow mounts over non-empty directories (like Linux), cp / -ax (destination) will not copy whole filesystem. In particular, content of /dev will not be usually copied, because distributions mount tmpfs over /dev. [Ok, there's hopefully better wording...?] But isn't that the entire purpose of -x? To avoid copying files on other file systems? I am just not sure about having a description that is don't copy files on other filesystems and then warning: does not copy files on other filesystems. I have never liked the wording of stay on this file system. Usually describing things in the positive, saying what it does, is best. But I always felt that with -x describing it in the negative, saying what it does not do, would be better wording. Bob
bug#14383: cp --one-file-system / will not copy whole root filesystem
Hi! But isn't that the entire purpose of -x? To avoid copying files on other file systems? I am just not sure about having a description that is don't copy files on other filesystems and then warning: does not copy files on other filesystems. I have never liked the wording of stay on this file system. Usually describing things in the positive, saying what it does, is best. But I always felt that with -x describing it in the negative, saying what it does not do, would be better wording. No no, I'm saying that it will not copy data on *this* filesystem; because other filesystem is mounted over those data. Lets say you have this on your / (ext3): / /dev/foo But your distro mounts devtmpfs over /dev, so /dev/foo is not visible, and not copied :-(. Not that cp can do much about that, but I tried to backup my / filesystem, and that's exactly what happened. Pavel -- (english) http://www.livejournal.com/~pavelmachek (cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
bug#14383: cp --one-file-system / will not copy whole root filesystem
On 05/10/2013 11:55 AM, Pavel Machek wrote: Hi! On systems like linux, cp / -a --one-file-system (destination) will not copy whole root filesystem. It is not cp's fault, but the behaviour is quite surprising to the users, so maybe it would be worth warning in man page? Something like -x, --one-file-system stay on this file system Note that on systems that allow mounts over non-empty directories (like Linux), cp / -ax (destination) will not copy whole filesystem. In particular, content of /dev will not be usually copied, because distributions mount tmpfs over /dev. [Ok, there's hopefully better wording...?] Well this issue is not restricted to -x of course, but I suppose it's might be a good place to put a warning. I suppose you could give the advice to ensure that all mounts in a tree should be unmounted to ensure that the base file system contents are copied. That info would be more appropriate in the texinfo manual, than the man page I would think. thanks, Pádraig.
bug#14383: cp --one-file-system / will not copy whole root filesystem
Pádraig Brady p...@draigbrady.com writes: I suppose you could give the advice to ensure that all mounts in a tree should be unmounted to ensure that the base file system contents are copied. The easiest way to uncover all over-mounted files of a filesystem is to bind-mount it somewhere else. Andreas. -- Andreas Schwab, sch...@linux-m68k.org GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 And now for something completely different.
bug#14383: cp --one-file-system / will not copy whole root filesystem
Andreas Schwab wrote: Pádraig Brady writes: I suppose you could give the advice to ensure that all mounts in a tree should be unmounted to ensure that the base file system contents are copied. The easiest way to uncover all over-mounted files of a filesystem is to bind-mount it somewhere else. I could see creating a section in the documentation as a HOWTO on copying filesystems from one place to another. But I don't think cp is the place to add code to do bind mounts so that an entire filesystem is copied. Also that is quite kernel specific behavior. It would be a portability nightmare. Also I think most users understand that the purpose of -x is to prevent crossing filesystem boundaries. Don't start walking down nfs mounted filesystems. Don't start walking down other mount points at all. And with it that means that anything that is shadowed will also not be copied. That has been the behavior since recursive copies and -x were added to cp. I know the suggestion wasn't to change the behavior of cp in this case to actually copied the shadowed files but to document it somehow so that the user is freshly aware of it. Wake them up so that it is fresh in their brain cache. If cp -v is used does cp report skipping mount points? That might be the best place to note this happening. Bob
