The meaning of the errors from the cpio command

cpioembeddedinitramfs

I have been using the following command on my system to create the .cpio archive to create an initramfs for my embedded target device

sudo find . | cpio -H newc -oc > ~/initramfs.cpio

This has always worked for me without any problem. Yesterday I was generating a new archive and I received the following error:

cpio: Archive format multiply defined: Operation not permitted
cpio: ./etc/shadow: Function open failed: Permission denied
cpio: ./usr/lib/ssh-keysign: Function open failed: Permission denied
64842 blocks

I never received these errors in the past, the files mentions with failed opens have not been touched either so I cannot understand why this has started happening. I update my host system with Ubuntu package manager so it is possible that my cpio package has been updated too. I obviously have no faith in the initramfs generated here due to all of the errors which confuse me greatly. The only option I can think of is to try and find out if my cpio version has changed and if so remove and replace with the older version I had. Is there any way I can find out this information on my system (Ubuntu 12.04)? Or is there some other way I can get around this problem?

Best Answer

The first error is because you're passing both -H newc and -c. You have to make up your mind on the format of the archive you want to generate. The "Operation not permitted" is a bug in GNU cpio, it's passing wrong arguments to the function that outputs that error message and should exit there.

The other errors are because you're not running that command as the superuser or more likely , you're not running it from the correct location. Only the superuser can read files like /etc/shadow as it contains sensitive information. You should also make sure that the archive you generate can only be read by the superuser. If it's an initramfs you're creating, chances are /etc/shadow has not business being there, unless that initramfs contains a full operating system.

Related Solutions

How would you use the cpio command

It is still relevant for unpacking RPMs. There is a rpm2cpio utility that converts an RPM package to a cpio archive. As far as I know, there is nothing to convert an RPM to a tar archive. Here is an example usage:

rpm2cpio myrpmfile.rpm | cpio -idmv

Is the busybox cpio THAT different from GNU cpio

The options that the BusyBox commands have depends a lot on the options that BusyBox is compiled with. BusyBox aims to be highly configurable so that very small cut down versions can be compiled for systems where resources are very limited. Larger, more full featured versions can be built where this isn't an issue.

In your case cpio needs the -p or --pass-through (long form) option enabled. Normally cpio behaves more like an archive utility like tar, however it also has an extra function which allows it to copy files. To enable this in BusyBox, it needs to be built with FEATURE_CPIO_P defined (also LONG_OPTS for long form options to be enabled for any program).

From your last question, I strongly recommend that you use rsync for what you are doing. You are probably better off asking another question detailing exactly what you are doing with rsync and why it doesn't do what you expect. rsync is an extremely versatile tool and can no doubt be configured to do what you want.

That said, you could try the following with cpio, this will create an archive and then extract it again (somewhat less efficient, but still the same result):

find . -mtime -2 | cpio -o | { cd /media/USB_FLASH_2 && cpio -imd; }

Unfortunately the -o option can also be disabled in BusyBox (FEATURE_CPIO_O build option), so this may not work either.

Update

Based on this line of output, you need to add an extra option when creating an archive:

    -o      Create (requires -H newc)

This changes the command to:

find . -mtime -2 | cpio -oH newc | { cd /media/USB_FLASH_2 && cpio -imd; }

This time I have tested with the cpio in the BusyBox for my own system and it works for me, however in some cases the mtimes for directories won't be preserved. rsync should be the best way to do this.

Best Answer

Related Solutions

How would you use the cpio command

Is the busybox cpio THAT different from GNU cpio

Update

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