Root Fix Permissions

[gmfausey]

Probably a silly questions to some but what does it mean/do when you use "fix permission" in CWM? Is this something that should be done at some point whether there's problems or not? Thanks for the info

 

[ZeroOne]

Hello hope this helps you
n Android, each app runs as its own UID (user ID) just like multiple people would have their own UID on a big UNIX system. The reasoning is the same, to prevent apps (people) from messing with each other's data. The data for each app has to be 'owned' by the UID the app runs as, and additionally the app itself (.apk file) has to be that same UID. Unlike big UNIX systems, these IDs are stored in the packages.xml file in /data/system. This file, in addition to storing UIDs, stores the android permissions of each program as described in its manifest (permissions like writing to the sdcard, monitoring phone state, turning wifi on and off, accessing bluetooth, etc). If the file is damaged, deleted, or otherwise unreadable, it is regenerated. The app UIDs are assigned initially in the order you install them (10001, 10002, etc.). When the packages.xml regenerates, it grabs the Android permissions from the .apks but doesn't know what the old UIDs were. That's where fix_permissions comes in.
Whether run from recovery or a booted system, fix_permissions reads through the packages.xml file and performs a chown/chmod command (which changes owner/change read-write-execute permissions) on each .apk and the data directory for it. It doesn't fix Android permissions (e.g. if phone.apk lost the ability to make calls, fix_permissions wouldn't help -- see below). While CyanogenMod udpates the version of fix_permissions in the ROM on a semi-regular basis, the version in any given recovery is probably older (and recoveries aren't upgraded on devices as often, either). So if fix_permissions in recovery doesn't work, the one in the booted rom might (or vice versa).

 

[MRCMidnight]

This is a great help. It saved me from reflashing a ROM or two as I couldnt root in File Manager while I was rooted like changing filenames at least. I didnt know what it did til I came here and read. Thanks for sharing.

~ Sent from my Triumph using Tapatalk ~

 

[Chairshot215]

Once had an issue with a few apps force closing after a CM7 update that was fixed after running Fix Permissions with Rom Manager, Gmail for the most part. I have made a point to run it after flashing updates that I do not wipe data or after a Rom Manager update. Have since not had any issues but can’t say I would have had any issues after as I just do it preemptively.

 

[thangfish]

Thanks for taking the time to post this, Zero one.
Agentc13 might need to link this in his sticky.