Setting up of PITR system.

Hi,

We are trying to setup PITR system based on documentation
http://www.postgresql.org/docs/8.1/interactive/backup-online.html

We have 3 questions regarding

1. Selection of archived WAL records that can be safely removed.
2. Knowing the relevant WAL record just after pg_stop_backup()
3. Recommended tool for taking file system level backup.

Elaboration:

we want to remove archived WAL log files which are no longer needed
so that the size of wal_archive folder is under control.

The DOCs say that filenames numerically less than the WAL record that
pg_stop_backup()
suggests can be removed. Will an alphabetical sorting be different from
numerically sorted
filename ? Sorting numerically is not easy as the filenames look like HEX
numbers
ut they are are so huge that they cant be stored in normal integers
(32bits).

Q2. We are attempting to automate the process of taking base backup and
removal
of the unneeded WAL files. Is there any reliable way of knowing the WAL
file X from
inside the shell script , such that files prior to X can be removed ?

from a shell script we issue pg_stop_backup() by psql -c , it returns
something
which does not looks like a WAL file.

Regds
Rajesh Kumar Mallah.