[Q] Why does the SU binary not work from /data ? topic

I'm trying to put the SU binary in a different place than the /system folder. I can flash it to /data with the correct permissions, but when I run SU, it doesn't get root.

Code:

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shell@android:/ $ /data/su
/data/su
1|shell@android:/ $ id
id
uid=2000(shell) gid=2000(shell) groups=1003(graphics),1004(input),1007(log),1009(mount),1011(adb),1015(sdcard_rw),3001(net_bt_admin),3002(net_bt),3003(inet),3006(net_bw_stats)

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Is there a reason why it doesn't work in /data/? Is there another folder (not /system/) where it should work?

Code:

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ls -la /data/su
-rwsr-sr-x root    root      380532 2008-08-01 12:00 su
# From a working /system/su :
-rwsr-sr-x root    root      380532 2008-08-01 12:00 su

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