Though granted storage permission file created not visible from Android

[573]

I have permitted nix storage access in Android settings.
When I touch /sdcard/test in nix and try to view test in Android's Files app it is not there.
In nix I can see the created file though.
I also restarted my device just in case, no change.

[t184256]

Weird, I tried that and I see the file with my file manager (Amaze).

[573]

@t184256 even with Amaze, no luck , file still not visible.
Are there debugging options ?

[t184256]

Debugging options for what?.. I can try to help troubleshooting it, I guess.

Does it work the other way? Create a directory in a file manager, do you see it there? What are the permissions of the file you've created with nix-on-droid? (Ideally viewed with ls -l and ls -lZ after su in a recovery session)

[573]

I see all files from inside nix, i. e. the created one:

-rw-rw---- 1 root 9997 ? 5 Oct 3 09:53 test

with recovery session do you mean that I restart my device in recovery mode ?

thanks for helping me troubleshoot this.

[t184256]

I meant exiting all Nix-on-Droid sessions and running a Nix (failsafe shell) one.

[573]

-rw-rw---- 1 root everybody u:object_r:sdcardfs:s0 5 2020-10-03 11:53 test

(output of ls -lZ /sdcard/)

[t184256]

Any differences for files created inside and outside of Nix-on-Droid?

[573]

created this file in Amaze.
It is not visible in failsafe session.

1|:/data/data/com.termux.nix/files/home $
ls -lZ /sdcard/test2
ls: /sdcard/test2: No such file or directory

[573]

Hold on I guess /sdcard is just the wrong device or link name:

1|:/data/data/com.termux.nix/files/home $
ls /storage/9016-4EF8/test2
/storage/9016-4EF8/test2

Using /storage/9016-4EF8 works but only in this direction: created outside nix, read inside nix.

[573]

other direction:

1|:/data/data/com.termux.nix/files/home $
touch /storage/9016-4EF8/test3
touch: '/storage/9016-4EF8/test3': Permission denied

1|:/data/data/com.termux.nix/files/home $
ls -lZ /storage/9016-4EF8/
ls: /storage/9016-4EF8//.android_secure: Permission denied
total 168800
drwxr-xr-x 2 root everybody u:object_r:sdcardfs:s0 32768 2020-07-13 18:07 Alarms

[t184256]

OK, now I have only two ideas. 1) Android >9 does storage isolation in some way I've never witnessed myself. 2) you're using some tricky fs-level 'combined storage' and discovered ways to write to different backing devices. What is mounted where?

[573]

Regarding 2) I do hope I am not ;)

/dev/root on / type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
tmpfs on /dev type tmpfs (rw,seclabel,nosuid,relatime,size=1385168k,nr_inodes=346292,mode=755)
devpts on /dev/pts type devpts (rw,seclabel,relatime,mode=600)
none on /dev/cpuctl type cgroup (rw,nosuid,nodev,noexec,relatime,cpu)
none on /dev/cpuset type cgroup (rw,nosuid,nodev,noexec,relatime,cpuset,noprefix,release_agent=/sbin/cpuset_release_agent)
none on /dev/memcg type cgroup (rw,nosuid,nodev,noexec,relatime,memory)
adb on /dev/usb-ffs/adb type functionfs (rw,relatime)
none on /dev/freezer type cgroup (rw,relatime,freezer)
proc on /proc type proc (rw,relatime,gid=3009,hidepid=2)
sysfs on /sys type sysfs (rw,seclabel,relatime)
selinuxfs on /sys/fs/selinux type selinuxfs (rw,relatime)
/sys/kernel/debug on /sys/kernel/debug type debugfs (rw,seclabel,relatime)
tracefs on /sys/kernel/debug/tracing type tracefs (rw,seclabel,relatime)
pstore on /sys/fs/pstore type pstore (rw,seclabel,nosuid,nodev,noexec,relatime)
none on /sys/kernel/config type configfs (rw,relatime)
tmpfs on /mnt type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1385168k,nr_inodes=346292,mode=755,gid=1000)
tmpfs on /mnt/sde type tmpfs (rw,seclabel,relatime,size=1385168k,nr_inodes=346292,mode=700)
/dev/block/mmcblk0p5 on /mnt/vendor/cpefs type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,noauto_da_alloc,i_version)
/dev/block/mmcblk0p3 on /mnt/vendor/efs type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,noauto_da_alloc,i_version)
/data/knox/secure_fs/enc_media on /mnt/shell/enc_emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1000,fsgid=1000,gid=9997,multiuser,derive_gid,default_normal,reserved=20MB)
/data/media on /mnt/runtime/default/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,multiuser,mask=6,derive_gid,default_normal,reserved=20MB,unshared_obb)
/data/media on /mnt/runtime/read/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=23,derive_gid,default_normal,reserved=20MB,unshared_obb)
/data/media on /mnt/runtime/write/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,reserved=20MB,unshared_obb)
/data/media on /mnt/runtime/full/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,reserved=20MB,unshared_obb)
/dev/block/vold/public:179,33 on /mnt/media_rw/9016-4EF8 type sdfat (rw,nosuid,nodev,noexec,noatime,fs=vfat:32,uid=1023,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,utf8,shortname=winnt,namecase=0,delay,smart,ausize=32768,adj_hid,adj_req,symlink=0,bps=512,errors=remount-ro)
/dev/block/vold/public:179,33 on /mnt/secure/asec type sdfat (rw,nosuid,nodev,noexec,noatime,fs=vfat:32,uid=1023,gid=1023,fmask=0007,dmask=0007,allow_utime=0020,codepage=cp437,iocharset=iso8859-1,utf8,shortname=winnt,namecase=0,delay,smart,ausize=32768,adj_hid,adj_req,symlink=0,bps=512,errors=remount-ro)
/mnt/media_rw/9016-4EF8 on /mnt/runtime/default/9016-4EF8 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=1015,mask=6,nocache)
/mnt/media_rw/9016-4EF8 on /mnt/runtime/read/9016-4EF8 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18,nocache)
/mnt/media_rw/9016-4EF8 on /mnt/runtime/write/9016-4EF8 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18,nocache)
/mnt/media_rw/9016-4EF8 on /mnt/runtime/full/9016-4EF8 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=7,nocache)
tmpfs on /apex type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1385168k,nr_inodes=346292,mode=755)
/dev/root on /apex/com.android.tzdata@290000000 type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.tzdata type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.runtime@1 type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.runtime type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.media@290000000 type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.media type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.media.swcodec@290000000 type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.media.swcodec type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.conscrypt@290000000 type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.conscrypt type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.resolv@290000000 type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/root on /apex/com.android.resolv type ext4 (ro,seclabel,nodev,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product/etc/permissions type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product/etc/permissions type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product/etc/sysconfig type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product/etc/sysconfig type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product/omc/DBT/etc/permissions type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-1 on /product/omc/DBT/etc/sysconfig type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
/dev/block/dm-2 on /vendor type ext4 (ro,seclabel,relatime,block_validity,discard,delalloc,barrier,user_xattr,acl,i_version)
none on /acct type cgroup (rw,nosuid,nodev,noexec,relatime,cpuacct)
none on /config type configfs (rw,nosuid,nodev,noexec,relatime)
/dev/block/mmcblk0p29 on /omr type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,noauto_da_alloc,i_version)
/dev/block/mmcblk0p28 on /cache type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,noauto_da_alloc,i_version)
/dev/block/mmcblk0p32 on /data type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,noauto_da_alloc,resgid=5678,i_version)
/dev/block/mmcblk0p4 on /efs type ext4 (rw,seclabel,nosuid,nodev,noatime,journal_checksum,noauto_da_alloc,i_version)
tmpfs on /storage type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1385168k,nr_inodes=346292,mode=755,gid=1000)
/data/media on /storage/emulated type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,multiuser,mask=7,derive_gid,default_normal,reserved=20MB,unshared_obb)
/mnt/media_rw/9016-4EF8 on /storage/9016-4EF8 type sdcardfs (rw,nosuid,nodev,noexec,noatime,fsuid=1023,fsgid=1023,gid=9997,mask=18,nocache)
tmpfs on /storage/self type tmpfs (rw,seclabel,nosuid,nodev,noexec,relatime,size=1385168k,nr_inodes=346292,mode=755,gid=1000)
s -lZ /storage/9016-4EF8/ <

[573]

that's a lot of spam for some mount command I guess.

[t184256]

Mmm, yeah, the amount of magic going on here is beyond me. My device has it much simpler.

You seem to have /mnt/media_rw/9016-4EF8 as the backing storage for /storage/9016-4EF8 and /sdcard, and then sdcardfs might impose some per-app isolation I guess? And the /mnt/runtime/{default,read,write,full}/{emulated,9016-4EF8} sounds fun as well.

I suggest starting with Termux first to determine the correct writable sdcard location first, it should be much more popular and much more documented, might even have a wizard command to set it up or something. And when you find one that works, then proceed with testing it with Nix-on-Droid.

[573]

I wanted to add that I can touch /mnt/sdcard/test3 in the non-failsafe, regular nix session and see the created file from outside although it's location is mapped to "internal storage" by Android (in Files app I see <internal storage>/test3).
Thus I'd say it definitely works from nix-on-droid's side.