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alex6
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Joined: 18 Jul 2011
Posts: 176
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 Posted: Sat Feb 08, 2014 3:21 pm Post subject: Problem with usage of cp |
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My goal is to make a backup but not erase existing files using cp.
After reading "man cp", I tried "cp -rn", but I have a strange output :
| Quote: | | cp: cannot create regular file ‘/mnt/plouf/alex32/Desktop/b/analysis/1765.libardourvampplugins:percussiononsets:2’: No such file or directory |
So it seems it can't create a file to the destination if the directory is not present...?
How can I do ?
I don't want to use rsync because it takes forever and I only want new files/directories to be copied |
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Hypnos
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| Posted: Sat Feb 08, 2014 3:35 pm Post subject: |
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rsync with the "-a" option only copies differences and preserves permissions, timestamps, etc. -- it's a proper backup.
cp with the "-a" option will do much the same.
These behaviors are described in the respective man pages.
If you want a scripted solution, check out my backup howto linked in my signature.
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Anon-E-moose
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Joined: 23 May 2008
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Location: Dallas area
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| Posted: Sat Feb 08, 2014 4:40 pm Post subject: |
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I've not noticed a lot of speed difference between rsync and cp -ap or cp-apu (copy only if newer)
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Hypnos
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| Posted: Sat Feb 08, 2014 5:42 pm Post subject: |
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| Anon-E-moose wrote: | | I've not noticed a lot of speed difference between rsync and cp -ap or cp-apu (copy only if newer) |
Which is faster? Are you making sure to compare across different filesystems, which is the usual application of rsync?
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toralf
Developer
Joined: 01 Feb 2004
Posts: 3922
Location: Hamburg
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| Posted: Sat Feb 08, 2014 6:25 pm Post subject: Re: Problem with usage of cp |
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| alex6 wrote: | My goal is to make a backup but not erase existing files using cp.
After reading "man cp", I tried "cp -rn", but I have a strange output :
| Quote: | | cp: cannot create regular file ‘/mnt/plouf/alex32/Desktop/b/analysis/1765.libardourvampplugins:percussiononsets:2’: No such file or directory |
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Check for an unusual file name and/or wgetpaste the whole command line + terminal output. |
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Anon-E-moose
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Joined: 23 May 2008
Posts: 6097
Location: Dallas area
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| Posted: Sat Feb 08, 2014 7:15 pm Post subject: |
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| Hypnos wrote: | | Anon-E-moose wrote: | | I've not noticed a lot of speed difference between rsync and cp -ap or cp-apu (copy only if newer) |
Which is faster? Are you making sure to compare across different filesystems, which is the usual application of rsync? |
Yes, I've actually used both across file systems on different disks.
I was manually running a cp -apu once a week or so, before I swapped to rsync run by cron.
There may be a time difference between them, but to me it's a small difference in my testing while getting rsync set up.
Note: I didn't time it with a stopwatch, just subjective waiting for it to finish.
Also these were on sata 2/3 to either the esata port or my usb3 backup disks.
Edit to add: if one uses the delete option of rsync, then it will be slower than a straight copy,
but will be comparable to a cp + rm of whatever files.
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Hypnos
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| Posted: Sat Feb 08, 2014 7:31 pm Post subject: |
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| Anon-E-moose wrote: | Edit to add: if one uses the delete option of rsync, then it will be slower than a straight copy,
but will be comparable to a cp + rm of whatever files. |
This would make sense, they're all using the same system calls to create and unlink files.
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Anon-E-moose
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| Posted: Sat Feb 08, 2014 7:54 pm Post subject: |
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Back to the original question.
I'm not sure what you were trying to do.
Can you post the whole cp command that you were using?
I can't tell from the message in the original post whether it was from the source or the destination.
Edit to add: As an example
cp -rn /src/dir_of_files /dest/
then /dest must exist and must be writable by whoever the user is and it will leave dir_of_files under /dest, ie /dest/dir_of_files
This hold true no matter how many levels of destination directories you have.
cp -rn /src/dir_of_files /dest/dir1/dir2
then /dest/dir1/dir2 all must exist.
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