[Android Q&A, Help & Troubleshooting] egandt:
First I'm on 7.1.1 LineageOS v20, I have my SD card formated using ext2 since I need 4+ GB files for TWRP backups. This works and I can create files and folder ..., however I've found that if I pull the SD card and on a computer set the permission to say 777 all is fine, but on the Phone, I can for instance create a directory using root-explorer, but can not set permission or copy files into it. If I create the folder on the computer I can copy files into it however. Next say I backup using Ti-backup to the external SDcard it works fine, but of I install a new ROm I can not access the previous backup files. I can not change the permissions on the file to 777 either from a terminal.

Really this is what upsets me, as root in a terminal I can not set permissions on a file as it does nothing, for instance on /storage/emulated/0 I have:

h918:/storage/emulated/0 # ls

drwxrwx--x 3 root sdcard_r 4096 Mar 14 19:35 .rr

-rw-rw---- 1 root sdcard_r 1369542927 Apr 1 22:28 01update.zip

-rw-rw---- 1 root sdcard_r 884357956 Apr 1 22:34 02update.zip

-rw-rw---- 1 root sdcard_r 1057588047 Apr 1 22:41 03update.zip

drwxrwx--x 2 root sdcard_r 4096 Mar 9 23:06 3DMarkAndroid

drwxrwx--x 2 root sdcard_r 4096 Mar 4 18:20 Alarms

....

as root I execute:

h918:/storage/emulated/0 # chmod 777 *.zip

h918:/storage/emulated/0 # chmod 777 *.zip

h918:/storage/emulated/0 # ls -al

drwxrwx--x 43 root sdcard_r 4096 Apr 1 22:35 .

drwx--x--x 4 root sdcard_r 4096 Jan 1 2016 ..

-rw-rw---- 1 root sdcard_r 2557 Apr 1 20:20 .bash_history

drwxrwx--x 3 root sdcard_r 4096 Mar 14 19:35 .rr

-rw-rw---- 1 root sdcard_r 1369542927 Apr 1 22:28 01update.zip

-rw-rw---- 1 root sdcard_r 884357956 Apr 1 22:34 02update.zip

-rw-rw---- 1 root sdcard_r 1057588047 Apr 1 22:41 03update.zip

drwxrwx--x 2 root sdcard_r 4096 Mar 9 23:06 3DMarkAndroid

drwxrwx--x 2 root sdcard_r 4096 Mar 4 18:20 Alarms

...

The permissions remain unchanged, why I'm root I should be able to change permissions.

looking at mount the options are:

/dev/fuse on /storage/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

/dev/fuse on /mnt/runtime/read/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

/dev/fuse on /mnt/runtime/write/emulated type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

The SD card looks similar:

/dev/fuse on /storage/ea8c26be-fcbc-4773-b799-5e64ef33f641 type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

/dev/fuse on /mnt/runtime/read/ea8c26be-fcbc-4773-b799-5e64ef33f641 type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

/dev/fuse on /mnt/runtime/write/ea8c26be-fcbc-4773-b799-5e64ef33f641 type fuse (rw,nosuid,nodev,noexec,noatime,user_id=1023,group_id=1023,default_permissions,allow_other)

Nothing here should block ROOT from change the permissions. I simply want as root or as any root application to be able to create a directory change file permission and access data written as another root app, all of which make it possible to use the phone and backup/restore safely.

I can only assume something is blocking me form using the device the way I want and operating on files, since pulling the card to a computer allows setting 777 and then it works as I want, what I want is to set the umask to 777 for everything, as for security that can be damned as I need to be able to backup and restore safely first, something I can not do now as Tibackup can not access it's own files on restore unless I first pull the card and set the permissions on a computer, which is unacceptable.

Files created on the phone have permissions 700 or something similar, even though on the phone they are listed as having more, this explains the issue as it is not for instance: -rw-rw---- but -rw-------, however root should still be able to access the file and can not, nor can root change the settings.

ERIC