[Android Q&A, Help & Troubleshooting] lucrus73:
Hello all,

I'm afraid I've just done a STUPID THING (TM) with my phone. In adb shell (root) I wanted to reformat the second partition of the *external* sd card, and I typed mmcblk0p2 instead of mmcblk1p2. I'm not sure I have broken anything, because fdisk does not show any mmcblk0p2 partition (see below), but the mkfs command somehow succeded:

# mkfs.ext2 /dev/block/mmcblk0p2
Filesystem label=
OS type: Linux
Block size=1024 (log=0)
Fragment size=1024 (log=0)
128 inodes, 1024 blocks
51 blocks (5%) reserved for the super user
First data block=1
Maximum filesystem blocks=262144
1 block groups
8192 blocks per group, 8192 fragments per group
128 inodes per group

and here is fdisk output:

# fdisk -l /dev/block/mmcblk0

Disk /dev/block/mmcblk0: 3909 MB, 3909091328 bytes
256 heads, 63 sectors/track, 473 cylinders
Units = cylinders of 16128 * 512 = 8257536 bytes

Device Boot Start End Blocks Id System
/dev/block/mmcblk0p1 1 266306 2147483647+ ee EFI GPT
Partition 1 has different physical/logical beginnings (non-Linux?):
phys=(0, 0, 1) logical=(0, 0, 2)
Partition 1 has different physical/logical endings:
phys=(1023, 255, 63) logical=(266305, 4, 4)

and the output of the mount command:

# mount
rootfs / rootfs ro,relatime 0 0
tmpfs /dev tmpfs rw,seclabel,nosuid,relatime,size=469568k,nr_inodes=117392,mode=755 0 0
devpts /dev/pts devpts rw,seclabel,relatime,mode=600 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,seclabel,relatime 0 0
selinuxfs /sys/fs/selinux selinuxfs rw,relatime 0 0
debugfs /sys/kernel/debug debugfs rw,relatime 0 0
none /sys/fs/cgroup tmpfs rw,seclabel,relatime,size=469568k,nr_inodes=117392,mode=750,gid=1000 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
tmpfs /mnt/asec tmpfs rw,seclabel,relatime,size=469568k,nr_inodes=117392,mode=755,gid=1000 0 0
/dev/block/dm-0 /mnt/asec/lysesoft.andsmb-1 ext4 ro,dirsync,seclabel,nosuid,nodev,noatime 0 0
tmpfs /mnt/obb tmpfs rw,seclabel,relatime,size=469568k,nr_inodes=117392,mode=755,gid=1000 0 0
/dev/block/platform/msm_sdcc.1/by-name/system /system ext4 ro,seclabel,relatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/userdata /data ext4 rw,seclabel,nosuid,nodev,noatime,discard,noauto_da_alloc,resuid=1000,errors=continue,data=ordered 0 0
/dev/block/vold/179:66 /data/sdext2 ext4 rw,seclabel,relatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/persist /persist ext4 rw,seclabel,nosuid,nodev,relatime,nodelalloc,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/cache /cache ext4 rw,seclabel,nosuid,nodev,noatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/drm /persist-lg ext4 rw,seclabel,nosuid,nodev,relatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/mpt /mpt ext4 rw,seclabel,nosuid,nodev,relatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/sns /sns ext4 rw,seclabel,nosuid,nodev,relatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.1/by-name/modem /firmware vfat ro,relatime,uid=1000,gid=1000,fmask=0337,dmask=0227,codepage=cp437,iocharset=iso8859-1,shortname=lower,errors=remount-ro 0 0
/dev/block/platform/msm_sdcc.1/by-name/cust /cust ext4 ro,seclabel,nodev,relatime,noauto_da_alloc,data=ordered 0 0
tmpfs /storage/emulated tmpfs rw,seclabel,nosuid,nodev,relatime,size=469568k,nr_inodes=117392,mode=050,gid=1028 0 0
/dev/fuse /mnt/shell/emulated fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/block/vold/179:65 /mnt/media_rw/external_SD vfat rw,dirsync,nosuid,nodev,noexec,relatime,uid=1023,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0
/dev/block/vold/179:65 /mnt/secure/asec vfat rw,dirsync,nosuid,nodev,noexec,relatime,uid=1023,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0
/dev/fuse /storage/external_SD fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/fuse /storage/emulated/0 fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/fuse /storage/emulated/0/Android/obb fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/fuse /storage/emulated/legacy fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/fuse /storage/emulated/legacy/Android/obb fuse rw,nosuid,nodev,relatime,user_id=1023,group_id=1023,default_permissions,allow_other 0 0
/dev/block/vold/179:65 /data/media/0/WhatsApp vfat rw,dirsync,nosuid,nodev,noexec,relatime,uid=1023,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0

Now the phone is still powered on, working ok, and connected with adb shell. I'm not rebooting it until I have some confidence I've not wiped essential system stuff. The phone has the LG stock ROM. Have I wiped any system partition? Will the phone boot again?