Possible to compress a TM backup file? [Mac Systems]

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From: Mark Conrad on 29 Mar 2010 13:01

I have a friend who is a newbie to Macs, he uses
Time Machine to create bootable backups.

Those backup files occupy a tremendous amount
of space. Compressing them would reduce their
space by about half.

My attempts to compress them were doomed to
failure because I do not have the smarts to handle
the various road blocks from the error messages
that pop up when I attempt to compress
the TM file, by using "Compress Archive".
(from the "File" menu)

Error message was something to the effect that
I did not have the necessary "permissions" for
some file named "spotlight_repair".

I could not locate that file anywhere on disk.

Mark-

From: nospam on 29 Mar 2010 12:06

From: nospam on 29 Mar 2010 12:09

From: Doug Anderson on 29 Mar 2010 12:43

Mark Conrad <aeiou(a)mostly.invalid> writes:

> I have a friend who is a newbie to Macs, he uses
> Time Machine to create bootable backups.
>
> Those backup files occupy a tremendous amount
> of space. Compressing them would reduce their
> space by about half.

This surprises me (that he can make bootable backups with Time
Machine).

The way Time Machine works by default is that it backs up your hard
drive (or those parts you've chosen to back up) once, and then every
hour makes a backup of only those files that have changed since the
previous backup.

So typically the initial backup is large (and time consuming), but it
doesn't grow that fast since typically one isn't changing or adding a
large number of files each hour.

As far as compression, if the backups are truly bootable (however your
friend has done that), they won't be after compression, right? So if
that is important, compression might be a bad idea.

As far as compressing Time Machine's archive, one of the advantages of
TM is that you can use TM to browse old file if necessary. I don't
know if this is going to work if you compress the archive. Almost
certainly if you compress the TM archive from outside of TM, it will
confuse TM, right?

I think if your friend's goal is to produce bootable backups, he
doesn't want to compress them, and he may not want to use Time Machine
for that purpose.

From: Kevin McMurtrie on 29 Mar 2010 14:12

In article <290320100901350163%aeiou(a)mostly.invalid>,
Mark Conrad <aeiou(a)mostly.invalid> wrote:

> I have a friend who is a newbie to Macs, he uses
> Time Machine to create bootable backups.
>
> Those backup files occupy a tremendous amount
> of space. Compressing them would reduce their
> space by about half.
>
> My attempts to compress them were doomed to
> failure because I do not have the smarts to handle
> the various road blocks from the error messages
> that pop up when I attempt to compress
> the TM file, by using "Compress Archive".
> (from the "File" menu)
>
> Error message was something to the effect that
> I did not have the necessary "permissions" for
> some file named "spotlight_repair".
>
> I could not locate that file anywhere on disk.
>
> Mark-

OS X has some access controls hacked in by filename. You might have to
enter the TM bundle on the command line, rename non-essential files,
then delete them.

TM might not be the right tool here. The backup format isn't very
robust so manipulation is only going to bring you trouble. You can boot
from a disk with a TM backup on it, but you can't directly boot a TM
backup. Restoring a bootable volume from a TM backup might require the
installation DVD.
--
I won't see Google Groups replies because I must filter them as spam

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