> I was wondering if it is safe to do a filesystem dump using the dump
> command on running databases such as postfix and mysql? Thanks.

Probably not if you expect to be able to recover the databases.  It
is extremely unlikely that the data files would be in a consistent state
at the time of the dump.

The same is true of using tar on open database files.

If you have enough disk space for a second copy of all the data in the
databases, you might try running some sort of database export utility
and backup the exports.  Or, you might run a replica database and shut
down the replica just prior to backing it up.

Database backups are a relatively frequent topic here, so you should
check the list archives for other solutions and suggestions.

-Ben

-- 
Benjamin Lewis <bhlewis AT purdue DOT edu>
Database Analyst/Programmer
IT Security and Policy - Computing Accounts
Purdue University