[Q] suggestions for backup of /efs directory?

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I have a Nexus S, on AT&T. upon flashing my first rom (CyanogenMod, via ROM Manager -- yes, I have since read comments that suggest that I should not use ROM Manager, and I will heed them), my IMEI got borked. at the suggestion of bedalus in this thread, I sent my phone back to Samsung and got it fixed.

I would like not to repeat the down time, so I've been surfing around, looking for a reliable way to back up that /efs directory, but I cannot find a definitive method.

at this link:
http://forum.xda-developers.com/show....php?t=1138873
the script simply does "adb pull /efs", and when I try this at my command line, I get complaints like this:

$ adb pull /efs
pull: building file list...
pull: /efs/nv_data.bin.md5 -> ./nv_data.bin.md5
failed to copy '/efs/nv_data.bin.md5' to './nv_data.bin.md5': Permission denied
pull: /efs/nv_data.bin -> ./nv_data.bin
failed to copy '/efs/nv_data.bin' to './nv_data.bin': Permission denied

so that didn't work. (I did do "adb shell", su, "cp -r /efs /mnt/sdcard/efs.backup" and that succeeded, so I figure that "adb pull" does not have root privs.) however, there is no way for me to confirm that what I have copied is actually correct. for instance, that nv_data.bin.md5 does not match the md5sum of nv_data.bin.

so I kept looking. this link:
http://forum.xda-developers.com/show....php?t=1074584
mentions using dd. so I typed "mount", found the device for my /efs partition like this:

# mount
...
/dev/block/mtdblock6 /efs yaffs2 rw,nosuid,nodev,relatime 0 0

whereupon I ran:

# dd if=/dev/block/mtdblock6 of=/mnt/sdcard/mtdblock6.img
dd if=/dev/block/mtdblock6 of=/mnt/sdcard/mtdblock6.img
13824+0 records in
13824+0 records out
7077888 bytes transferred in 2.138 secs (3310518 bytes/sec)

from my experience with Linux, I figure this last method is the safest, but I'm a bit skittish on flashing a new rom (which caused the whole IMEI problem...), unless I can get some sort of corroboration on whether I can expect this to work in reverse as a method of fixing a bad IMEI, if I should find myself back in the same situation.

any suggestions?

Originally Posted by krodrigu

....
any suggestions?

How about using 'Android Commander by PanPiotr' to pull the /efs folder to your PC ?

---------- Post added at 05:54 AM ---------- Previous post was at 05:39 AM ----------

Look HERE as well..

There's no reason why you can't copy the efs folder* to your sdcard then copy it normally via USB.

*using terminal emulator or root explorer

Obscurely referenced from the fifth dimension on my Nexus S

Originally Posted by bedalus

There's no reason why you can't copy the efs folder* to your sdcard then copy it normally via USB.

*using terminal emulator or root explorer

Obscurely referenced from the fifth dimension on my Nexus S

The only problem is, if you use term emulator or root explorer to copy /efs to the sdcard, you loose the permissions and ownership settings of the files.

Originally Posted by ethan_hines

The only problem is, if you use term emulator or root explorer to copy /efs to the sdcard, you loose the permissions and ownership settings of the files.

chmod 755 for almost everything but a few that are 666. When in doubt, chmod 755 everything. At worst, it could get --*gasp*-- deleted by a rogue app. But then you'd paste it again.