A terminal command for a rooted Android to remount /System as read/write

Question

I'm writing an android app that needs to copy a file to the "/system" partition at runtime. I've got the commands to run "su" and can successfully request SuperUser permissions and run commands as root. But I don't know how to make this app universal across multiple devices, because the mount command can differ depending on where the /system is actually mounted. Here's the command that's used most offen:

mount -o remount,rw -t yaffs2 /dev/block/mtdblock3 /system

But I know that mtdblock3 could be different on some devices (and for that matter, i guess so could yaffs2). So, my question is: Is there a universal command that will work on all phones? Or is there a way to find out at runtime what the correct parameters are?

Answer 1

You can run the mount command without parameter in order to get partition information before constructing your mount command. Here is an example of the mount command without parameter outputed from my HTC Hero.

$ mount
mount
rootfs / rootfs ro 0 0
tmpfs /dev tmpfs rw,mode=755 0 0
devpts /dev/pts devpts rw,mode=600 0 0
proc /proc proc rw 0 0
sysfs /sys sysfs rw 0 0
tmpfs /sqlite_stmt_journals tmpfs rw,size=4096k 0 0
none /dev/cpuctl cgroup rw,cpu 0 0
/dev/block/mtdblock3 /system yaffs2 rw 0 0
/dev/block/mtdblock5 /data yaffs2 rw,nosuid,nodev 0 0
/dev/block/mtdblock4 /cache yaffs2 rw,nosuid,nodev 0 0
/dev/block//vold/179:1 /sdcard vfat rw,dirsync,nosuid,nodev,noexec,uid=1000,gid=
1015,fmask=0702,dmask=0702,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,s
hortname=mixed,utf8,errors=remount-ro 0 0

Answer 2

I use this command:

mount -o rw,remount /system

Answer 3

Try

mount -o remount,rw /system

If no error message is printed, it works.

Or, you should do the following.

First, make sure the fs type.

mount

Issue this command to find it out.

Then

mount -o rw,remount -t yaffs2 /dev/block/mtdblock3 /system

Note that the fs(yaffs2) and device(/dev/block/mtdblock3) are depend on your system.

Answer 4

Instead of

mount -o rw,remount /system/

use

mount -o rw,remount /system

mind the '/' at the end of the command. you ask why this matters? /system/ is the directory under /system while /system is the volume name.

Answer 5

You don't need to pass both arguments when performing a remount. You can simply pass the mount point (here /system). And /system is universal amongst Android devices.

Answer 6

You can try adb remount command also to remount /system as read write

adb remount

Answer 7

I had the same problem. So here is the real answer: Mount the system under /proc. Here is my command:

mount -o rw,remount /proc /system

It works, and in fact is the only way I can overcome the Read-only System problem.

Answer 8

This is what works on my first generation Droid X with Android version 2.3.4. I suspect that this will be universal. Steps:

1. root system and install su.

2. Install busybox

3. Install a terminal program.

4. to mount system rw first su then

   busybox mount -o rw,remount system
   

5. To remount ro

   busybox mount -o ro,remount system
   

Note that there are no slashes on "system".

Answer 9

If you have rooted your phone, but so not have busybox, only stock toybox, here a one-liner to run as root :

mount -o rw,remount $( mount | sed '/ /system /!d' | cut -d " " -f 1 ) /system

toybox do not support the "-o remount,rw" option

if you have busybox, you can use it :

busybox mount -o remount,rw /system