[General Questions and Answers] cnexpat:
First how to find location of boot image in device? I want to take current boot image. Do modifications and later flash that boot image back to device.

I have searched correct block device and did some image files with dd command but they were not boot images. I tried with several tools.

Here is some listing from the phone with adb shell commands.

root@android:/proc # cat partitions
major minor #blocks name

179 0 30512256 mmcblk0
179 1 1 mmcblk0p1
179 2 10240 mmcblk0p2
179 3 10240 mmcblk0p3
179 4 6144 mmcblk0p4
179 5 665600 mmcblk0p5
179 6 129024 mmcblk0p6
179 7 1572864 mmcblk0p7
179 8 28077696 mmcblk0p8
179 64 2048 mmcblk0boot1
179 32 2048 mmcblk0boot0

root@android:/ # ls -l /emm*
lrwxrwxrwx root root 1970-01-01 06:30 emmc@android -> /dev/block/mmcblk0p5
lrwxrwxrwx root root 1970-01-01 06:30 emmc@cache -> /dev/block/mmcblk0p6
lrwxrwxrwx root root 1970-01-01 06:30 emmc@ebr1 -> /dev/block/mmcblk0p1
lrwxrwxrwx root root 1970-01-01 06:30 emmc@fat -> /dev/block/mmcblk0p8
lrwxrwxrwx root root 1970-01-01 06:30 emmc@protect_f -> /dev/block/mmcblk0p2
lrwxrwxrwx root root 1970-01-01 06:30 emmc@protect_s -> /dev/block/mmcblk0p3
lrwxrwxrwx root root 1970-01-01 06:30 emmc@sec_ro -> /dev/block/mmcblk0p4
lrwxrwxrwx root root 1970-01-01 06:30 emmc@usrdata -> /dev/block/mmcblk0p7
root@android:/ #

root@android:/dev/block # ls -al
brw------- root root 7, 0 2014-03-12 12:54 loop0
brw------- root root 7, 1 2014-03-12 12:54 loop1
brw------- root root 7, 2 2014-03-12 12:54 loop2
brw------- root root 7, 3 2014-03-12 12:54 loop3
brw------- root root 7, 4 2014-03-12 12:54 loop4
brw------- root root 7, 5 2014-03-12 12:54 loop5
brw------- root root 7, 6 2014-03-12 12:54 loop6
brw------- root root 7, 7 2014-03-12 12:54 loop7
brw-rw---- root system 179, 0 2014-03-12 12:54 mmcblk0
brw------- root root 179, 32 2014-03-12 12:54 mmcblk0boot0
brw------- root root 179, 64 2014-03-12 12:54 mmcblk0boot1
brw------- root root 179, 1 2014-03-12 12:54 mmcblk0p1
brw-r----- root system 179, 2 2014-03-12 12:54 mmcblk0p2
brw------- root root 179, 3 2014-03-12 12:54 mmcblk0p3
brw------- root root 179, 4 2014-03-12 12:54 mmcblk0p4
brw------- root root 179, 5 2014-03-12 12:54 mmcblk0p5
brw------- root root 179, 6 2014-03-12 12:54 mmcblk0p6
brw------- root root 179, 7 2014-03-12 12:54 mmcblk0p7
brw------- root root 179, 8 2014-03-12 12:54 mmcblk0p8
drwxr-xr-x root root 2014-03-12 12:54 platform
root@android:/dev/block #

/dev/block/mmcblk0boot0 looked promising but I made image of it by by command dd if=/dev/block/mmcblk0boot0 of=/sdcard/boot.img

But the image was not boot image.

root@android:/ # mount
rootfs / rootfs ro,relatime 0 0
tmpfs /dev tmpfs rw,nosuid,relatime,mode=755 0 0
devpts /dev/pts devpts rw,relatime,mode=600 0 0
proc /proc proc rw,relatime 0 0
sysfs /sys sysfs rw,relatime 0 0
none /acct cgroup rw,relatime,cpuacct 0 0
tmpfs /mnt/obb tmpfs rw,relatime,mode=755,gid=1000 0 0
emmc@android /system ext4 ro,noatime,noauto_da_alloc,commit=1,data=ordered 0 0
emmc@usrdata /data ext4 rw,nosuid,nodev,noatime,nodelalloc,noauto_da_alloc,commit=1,data=ordered 0 0
/emmc@protect_f /protect_f ext4 rw,nosuid,nodev,noatime,nodelalloc,noauto_da_alloc,commit=1,data=ordered 0 0
/emmc@protect_s /protect_s ext4 rw,nosuid,nodev,noatime,nodelalloc,noauto_da_alloc,commit=1,data=ordered 0 0
/emmc@fat /storage/sdcard0 vfat rw,dirsync,relatime,uid=1000,gid=1015,fmask=0702,dmask=0702,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,shortname=mixed,utf8,errors=remount-ro 0 0
root@android:/ #

I can make full image by dding /dev/block/mmcblk0 but it would be better to get the parts separately.

Is there easy way to find where the boot image is located?