Changing '/opt/.filetool.lst' does only indirectly influence what happens with the restoration, as is only controls what goes into the backup file. That obviously requires to execute a backup (e.g. filetool.sh -b or at shutdown). Otherwise the old 'mydata.tgz' is still around, and unless you are using bootcode 'norestore' don't be surprised that the old files are re-appearing. You really need to check the contents of your 'mydata.tgz'.
I've now done a re-test of my earlier advice and like to offer the following as a "proof" of that recommendation:
tc@box:~$ date > file
tc@box:~$ ls -l file
-rw-r--r-- 1 tc staff 29 Sep 16 04:20 file
tc@box:~$ echo file > list
tc@box:~$ rm -f a.tgz ; busybox tar czvf a.tgz -T list ; echo $? ; ls -l a.tgz
file
0
-rw-r--r-- 1 tc staff 127 Sep 16 04:21 a.tgz
tc@box:~$ tar tzvf a.tgz
-rw-r--r-- tc/staff 29 2010-09-16 04:20:52 file
This is the "normal" case: an entry in the list file results in a non-empty archive file.
tc@box:~$ rm -f list
tc@box:~$ rm -f a.tgz ; busybox tar czvf a.tgz -T list ; echo $? ; ls -l a.tgz
tar: can't open 'list': No such file or directory
1
ls: a.tgz: No such file or directory
Having no list file leads to the failure of the 'tar' command, and no archive file gets created.
tc@box:~$ rm -f list ; touch list
tc@box:~$ ls -l list
-rw-r--r-- 1 tc staff 0 Sep 16 04:22 list
tc@box:~$ rm -f a.tgz ; busybox tar czvf a.tgz -T list ; echo $? ; ls -l a.tgz
tar: empty archive
1
ls: a.tgz: No such file or directory
Having an empty list file will still results in a failure and the lack of an archive file.
tc@box:~$ echo ' ' > list
tc@box:~$ rm -f a.tgz ; busybox tar czvf a.tgz -T list ; echo $? ; ls -l a.tgz
tar: : No such file or directory
tar: error exit delayed from previous errors
1
-rw-r--r-- 1 tc staff 29 Sep 16 04:23 a.tgz
tc@box:~$ tar tzvf a.tgz
tc@box:~$ echo $?
0
tc@box:~$
Having just a single blank character as an entry in the list file results still in a warning from 'tar', but this time at least an empty archive file gets created.
BTW, it would be enough to do echo > list as the 'echo' command produces in any case a linefeed and hence the list file would not be empty.