Probable cause that remount fails is you are not running adb as root.
Shell Script should be as follow.
# Script to mount Android Device as read/write.
# List the Devices.
adb devices;
# Run adb as root (Needs root access).
adb root;
# Since you're running as root su is not required
adb shell mount -o rw,remount /;
If this fails, you could try the below:
# List the Devices.
adb devices;
# Run adb as root
adb root;
adb remount;
adb shell su -c "mount -o rw,remount /";
To find which user you are:
$ adb shell whoami
In addition to all the other answers you received, I want to explain the unknown option -- o error: Your command was
$ adb shell 'su -c mount -o rw,remount /system'
which calls su through adb. You properly quoted the whole su command in order to pass it as one argument to adb shell. However, su -c <cmd> also needs you to quote the command with arguments it shall pass to the shell's -c option. (YMMV depending on su variants.) Therefore, you might want to try
$ adb shell 'su -c "mount -o rw,remount /system"'
(and potentially add the actual device listed in the output of mount | grep system before the /system arg – see the other answers.)
I had the same problem and could not mount system as read/write. It would return
Usage: mount [-r] [-w] [-o options] [-t type] device directory
Or
operation not permitted. Access denied
Now this works on all rooted devices.
DO THE FOLLOWING IN TERMINAL EMULATOR OR IN ADB SHELL
$ su
#mount - o rw,remount -t yaffs2 /system
Yaffs2 is the type of system partition. Replace it by the type of your system partition as obtained from executing the following
#cat /proc/mounts
Then check where /system is appearing from the lengthy result
Extract of mine was like
mode=755,gid=1000 0 0
tmpfs /mnt/obb tmpfs rw,relatime,mode=755,gid=1000 0 0
none /dev/cpuctl cgroup rw,relatime,cpu 0 0/dev/block/platform/msm_sdcc.3/by-num/p10 /system ext4 ro,relatime,data=ordered 0 0
/dev/block/platform/msm_sdcc.3/by-num/p11 /cache ext4 rw,nosuid,nodev,relatime,data=ordered 0 0
So my system is ext4. And my command was
$ su
#mount -o rw,remount -t ext4 /system
Done.
I could not get the mount command to work without specifying the dev block to mount as /system
#cat /proc/mounts returns ( only the system line here )
/dev/stl12 /system rfs ro,relatime,vfat,log_off,check=no,gid/uid/rwx,iocharset=utf8 0 0
so my working command is
mount -o rw,remount -t rfs /dev/stl12 /system
mount -o rw,remount $(mount | grep /dev/root | awk '{print $3}')
this does the job for me, and should work for any android version.
Get "adbd insecure" from google play store, it helps give write access to custom roms that have it secured my the manufacturers.
The following may help (study the impacts of disable-verity first):
adb root
adb disable-verity
adb reboot
Otherwise... if
getenforce
returns
Enforcing
Then maybe you should call
setenforce 0
mount -o rw,remount /system
setenforce 1
Source: Stackoverflow.com