Why can't I delete or move these files without sudo?

I had used file-roller to extract an ISO image to my Desktop earlier, but now I can not delete or move/rename those files any more "as myself", only with sudo. Changing permissions (chmod) or content is possible though.

bytecommander@BC-AlkaliMetal:~/Desktop$ ll AUTORUN.INF 
-rwxr-xr-x 1 bytecommander bytecommander 132 Jul 21  2005 AUTORUN.INF*

bytecommander@BC-AlkaliMetal:~/Desktop$ chmod 777 AUTORUN.INF 

bytecommander@BC-AlkaliMetal:~/Desktop$ echo "Something useless" > AUTORUN.INF

bytecommander@BC-AlkaliMetal:~/Desktop$ cat AUTORUN.INF 
Something useless

bytecommander@BC-AlkaliMetal:~/Desktop$ ll AUTORUN.INF 
-rwxrwxrwx 1 bytecommander bytecommander 18 Sep 22 21:13 AUTORUN.INF*

bytecommander@BC-AlkaliMetal:~/Desktop$ rm AUTORUN.INF 
rm: cannot remove 'AUTORUN.INF': Permission denied

However, I would like to understand what exactly is holding me back here though.

My Desktop directory is on an ext4 partition. Output from mount:

/dev/sdb5 on / type ext4 (rw,noatime,nodiratime,errors=remount-ro,data=ordered)

I could not find any suspicious permissions, ACLs, extended attributes or anything else I know of though:

bytecommander@BC-AlkaliMetal:~/Desktop$ stat AUTORUN.INF 
  File: 'AUTORUN.INF'
  Size: 18          Blocks: 8          IO Block: 4096   regular file
Device: 815h/2069d  Inode: 405817      Links: 1
Access: (0777/-rwxrwxrwx)  Uid: ( 1000/bytecommander)   Gid: ( 1000/bytecommander)
Access: 2016-09-22 18:18:36.569110000 +0200
Modify: 2016-09-22 21:13:26.821382722 +0200
Change: 2016-09-22 21:26:16.653296674 +0200
 Birth: -

bytecommander@BC-AlkaliMetal:~/Desktop$ getfacl AUTORUN.INF 
# file: AUTORUN.INF
# owner: bytecommander
# group: bytecommander
user::rwx
group::rwx
other::rwx

bytecommander@BC-AlkaliMetal:~/Desktop$ lsattr AUTORUN.INF 
-------------e-- AUTORUN.INF

What is going on here?

Solution 1:

Removing a file requires write permission in its parent directory - so may fail if either

• ~/Desktop/ has has incorrect permission bits
• ~/Desktop/ has correct permissions but has become owned by someone else such as root

Check and adjust as necessary.