Se você não puder excluir um arquivo mesmo depois de ter chmod
'editado para 777, o problema pode estar no diretório em que o arquivo está. Por exemplo:
# no permission to write in the current directory...
$ ls -la
total 0
dr-xr-xr-x 3 chrisaycock staff 102 Jan 12 02:00 ./
drwxr-xr-x+ 59 chrisaycock staff 2006 Jan 12 01:59 ../
-rw-r--r-- 1 chrisaycock staff 0 Jan 12 02:00 test.txt
# ... and thus I can't delete a file in this directory
$ rm test.txt
rm: test.txt: Permission denied
# so I give myself permission to write
$ chmod u+w .
# just to confirm that I can write in this directory
$ ls -la
total 0
drwxr-xr-x 3 chrisaycock staff 102 Jan 12 02:00 ./
drwxr-xr-x+ 59 chrisaycock staff 2006 Jan 12 01:59 ../
-rw-r--r-- 1 chrisaycock staff 0 Jan 12 02:00 test.txt
# and now I can remove the file
$ rm test.txt