Optional flag|parameter for linux paths?

I’ve read a few places in these forums about using the /optional parameter so as not to stop on index errors -I am seeing index errors that seem to be stopping backups on a few of my linux clients and thought passing the optional flag might fix this.
Is there a way to pass this parameter on linux clients?

Thanks for your time.

Because ‘/’ is the directory separator under Linux, you MUST precede the flag with a directory alias. Here’s what I have to do under server version v2.4.15.0:

Default directories to backup: /|rootfs/symlinks_optional,share_hashes,optional

Also, in my experience, the ‘;’ is a directory separator not a directory terminator, eg, you may not have a terminating ‘;’ on the line above.

Also, I found ‘optional’ had to be at the end of the list.