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How to backup efs

Added by ariel enter over 6 years ago

I'm trying to backup my EFS partition since I heard it is possible to lose the IMEI

I want to show you how I did it and ask you guys if it was enough.

By using adb for the following steps, I started by listing all the available partitions with "df" witch gave me the following result:

$ adb shell df
Filesystem                    1K-blocks    Used Available Use% Mounted on
tmpfs                            402412      72    402340   1% /dev
none                             402412       8    402404   1% /sys/fs/cgroup
tmpfs                            402412       0    402412   0% /mnt
/dev/block/mmcblk0p9            1032088  472452    559636  46% /system
/dev/block/mmcblk0p7             100784    4180     96604   5% /cache
/dev/block/mmcblk0p1              20144   14596      5548  73% /efs
/dev/block/mmcblk0p10           3096320  312136   2784184  11% /data
/dev/block/mmcblk0p12            516040  373968    142072  73% /preload
/dev/block/vold/public:179_11  10483696    5656  10478040   1% /mnt/media_rw/34C8-6CDB
/dev/fuse                      10483696    5656  10478040   1% /mnt/runtime/default/34C8-6CDB
/dev/fuse                      10483696    5656  10478040   1% /mnt/runtime/read/34C8-6CDB
/dev/fuse                      10483696    5656  10478040   1% /mnt/runtime/write/34C8-6CDB
/dev/block/vold/public:179_13  15541408 1355448  14185960   9% /mnt/media_rw/DC27-7413
/dev/fuse                      15541408 1355448  14185960   9% /mnt/runtime/default/DC27-7413
/dev/fuse                      15541408 1355448  14185960   9% /mnt/runtime/read/DC27-7413
/dev/fuse                      15541408 1355448  14185960   9% /mnt/runtime/write/DC27-7413

I found that /efs was hold in /dev/block/mmcblk0p1 and that /mnt/media_rw/DC27-7413 was my external sd card, so I used dd to make an image of efs there:

$ adb shell dd if=/dev/block/mmcblk0p1 of=/mnt/media_rw/DC27-7413/efs_backup bs=512

Was this enough to backup my IMEI? I read in some other forums that there should be a modemfs also, but I don't see it on the list of partitions. Hopefully it didn't got missing after some issues I'm having with my phone.


Replies (3)

RE: How to backup efs - Added by Art Os over 6 years ago

for i9300, this command give the partition table :

adb shell ls -al /dev/block/platform/dw_mmc/by-name

RE: How to backup efs - Added by Xan VFR over 6 years ago

To backup /efs partition, because I lost IMEI a couple of times, I did

adb root
adb pull /efs .

When I had to restore /efs partition I "adb pushed" efs copy in my computer into my phone.

RE: How to backup efs - Added by Fil Lupin over 2 years ago

Hi,
there is now a page describing how to backup EFS : https://redmine.replicant.us/projects/replicant/wiki/BackupTheEFS

However, I encountered a problem while following instructions:

$ adb shell "mount /dev/block/platform/*/by-name/EFS /efs" 
$ adb pull /efs/ efs
/efs/: 31 files pulled. 2.6 MB/s (6353339 bytes in 2.310s)
$ adb shell "umount /efs" 
$ adb shell "rmdir /efs" rmdir: /efs: Read-only file system
$ adb shell "cat /dev/block/platform/*/by-name/EFS > /EFS.img" 
/system/bin/sh: can't create /EFS.img: Read-only file system

rmdir /efs does not work while mkdir /efs has worked, I wonder if it's a symptom for another issue

It works when replacing last line by 

adb shell "cat /dev/block/platform/*/by-name/EFS > /sdcard/EFS.img"

To restore backup:

adb shell "cat /sdcard/EFS.img > /dev/block/platform/dw_mmc/by-name/EFS"

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