[conspire] PING (Partimage Is Not Ghost) -- Backup and Restore Disk Partitions

[Rick Moen]

Quoting Daniel Gimpelevich (daniel at gimpelevich.san-francisco.ca.us):

> The question to ask here is "Is it the files I want safe, or some
> arbitrary filesystem metadata which may include those files?" The question
> of how to back stuff up for restoration somewhere else comes up quite
> frequently at CABAL, and I typically always say to use tar.

Rare indeed is the situation where you actually care about anything
_other_ than files/directories.  For example, replicating boot
information is often at best useless, because the stored disk geometry
will in the general case be wrong after replication to a new drive.
Also, capturing filesystem metadata strikes me as being (absent some
extraordinary need that I cannot current think of) perverse, because a
filesystem created from scratch by native tools (e.g., mkfs.ext3) will
tend to have metadata structures far, far more reliable than one that
has been in service for years.

> Utilities like Ghost usually do not use bit-for-bit copies of whole
> filesystems, but rather their own tar-like formats with additions for
> boot sectors and other whole-filesystem elements tacked on.

According to the Partimage FAQ, Ghost captures files + the boot
sector.[1]  Partimage, by contrast, captures used blocks without needing to
understand filesystem semantics.  So, those are actually somewhat more
diverse than I'd thought (I have no experience with the former, and only
a litte with the latter) -- but both of them are far too baroque a
solution for my liking, generally:  I want "Just the files, ma'am."  
(NTFS is not a concern, in my usage scenario.  Ownership, permissions, 
special files, and extended attributes are.)

> This is a shorter synonym:
> tar Scp -C dir . | tar Sxvp -C /mnt/somewhere

Again, that is _not_ the same:  The earlier syntax verifies that the
source and destination dirs exist and are available.  One learns after
various mishaps that such precautions are worth the trouble.

> Using "j" instead of "z" gives bzip2 instead of gzip:
> tar Scjp -C dir . | ssh username at newhost 'tar Sxvjp -C /mnt/somewhere'

At the cost of absolutely hideous performance overhead that is seldom
possible to justify for the 10% gain in compression.

[1] However, by contrast, this article claims it attempts to capture
full metadata:
http://www.computerpoweruser.com/editorial/article.asp?article=articles%2Farchive%2Fc0505%2F41c05%2F41c05.asp