<s>
Proxmox	B-Application
Backup	I-Application
Server	I-Application
(	O
short	O
Proxmox	O
BS	O
)	O
is	O
an	O
open-source	B-License
backup	B-Protocol
software	O
project	O
supporting	O
virtual	B-Architecture
machines	I-Architecture
,	O
containers	B-Application
,	O
and	O
physical	O
hosts	O
.	O
</s>
<s>
The	O
Bare-metal	B-General_Concept
server	I-General_Concept
is	O
based	O
on	O
the	O
Debian	O
Linux	B-Operating_System
distribution	O
,	O
with	O
some	O
extended	O
features	O
,	O
such	O
as	O
out-of-the-box	O
ZFS	B-Application
support	O
and	O
Linux	B-Operating_System
kernel	I-Operating_System
5.4	O
LTS	O
.	O
</s>
<s>
Proxmox	B-Application
Backup	I-Application
Server	I-Application
is	O
licensed	O
under	O
the	O
GNU	B-Application
Affero	I-Application
General	I-Application
Public	I-Application
License	I-Application
,	O
version	O
3	O
.	O
</s>
<s>
Proxmox	B-Application
Backup	I-Application
Server	I-Application
is	O
written	O
mostly	O
in	O
Rust	B-Application
and	O
implements	O
data	B-General_Concept
deduplication	I-General_Concept
to	O
reduce	O
the	O
storage	O
space	O
needed	O
.	O
</s>
<s>
Development	O
of	O
Proxmox	O
Backup	B-Protocol
originally	O
began	O
in	O
October	O
2018	O
to	O
provide	O
more	O
efficient	O
backup	B-Protocol
for	O
the	O
virtualization	O
platform	O
Proxmox	B-Language
Virtual	I-Language
Environment	I-Language
than	O
the	O
integrated	O
vzdump	O
backup	B-Protocol
tool	O
which	O
only	O
allows	O
full	B-Protocol
backups	I-Protocol
.	O
</s>
<s>
Proxmox	O
Backup	B-Protocol
uses	O
a	O
client-server	B-Operating_System
model	I-Operating_System
where	O
the	O
server	O
stores	O
the	O
backup	B-Protocol
data	O
.	O
</s>
<s>
The	O
client	O
tool	O
works	O
on	O
most	O
modern	O
Linux	B-Operating_System
systems	O
.	O
</s>
<s>
Proxmox	B-Application
Backup	I-Application
Server	I-Application
also	O
provides	O
a	O
REST	O
API	O
for	O
third	O
party	O
tools	O
.	O
</s>
<s>
Proxmox	B-Application
Backup	I-Application
Server	I-Application
supports	O
incremental	B-General_Concept
backups	I-General_Concept
,	O
data	B-General_Concept
deduplication	I-General_Concept
,	O
Zstandard	B-Language
compression	O
and	O
authenticated	B-Algorithm
encryption	I-Algorithm
(	O
AE	O
)	O
.	O
</s>
<s>
The	O
first	O
backup	B-Protocol
is	O
a	O
full	B-Protocol
backup	I-Protocol
,	O
and	O
subsequent	O
backups	B-Protocol
are	O
sent	O
incrementally	O
from	O
the	O
client	O
to	O
the	O
Proxmox	B-Application
Backup	I-Application
Server	I-Application
,	O
where	O
data	O
is	O
deduplicated	O
.	O
</s>
<s>
For	O
the	O
Proxmox	B-Language
VE	I-Language
platform	O
,	O
the	O
Proxmox	O
Backup	B-Protocol
client	O
is	O
tightly	O
integrated	O
;	O
the	O
backup	B-Protocol
storage	I-Protocol
is	O
configurable	O
as	O
a	O
storage	O
backend	O
on	O
a	O
Proxmox	B-Language
VE	I-Language
node	O
and	O
supports	O
deduplicated	O
backups	B-Protocol
of	O
QEMU	B-Application
virtual	B-Architecture
machines	I-Architecture
and	O
LXC	B-Application
containers	B-Application
.	O
</s>
<s>
The	O
platform	O
also	O
leverages	O
QEMU	B-Application
dirty-bitmaps	O
,	O
which	O
allows	O
for	O
fast	O
backups	B-Protocol
from	O
the	O
Proxmox	B-Language
VE	I-Language
client	O
to	O
the	O
server	O
,	O
as	O
the	O
disk	O
images	O
do	O
not	O
need	O
to	O
be	O
scanned	O
for	O
changes	O
.	O
</s>
<s>
Backups	B-Protocol
can	O
be	O
stored	O
on-premises	O
or	O
synchronized	O
to	O
remote	O
locations	O
with	O
Remotes	O
,	O
and	O
multiple	O
,	O
unrelated	O
hosts	O
can	O
use	O
the	O
same	O
backup	B-Protocol
server	O
.	O
</s>
<s>
All	O
client-server	B-Operating_System
traffic	O
is	O
transferred	O
over	O
TLS-1.3	B-Protocol
to	O
protect	O
against	O
eavesdropping	O
.	O
</s>
<s>
To	O
further	O
protect	O
backup	B-Protocol
data	O
at	O
rest	O
,	O
optional	O
encryption	O
of	O
all	O
backed-up-data	O
is	O
available	O
using	O
AES-256	B-Algorithm
in	O
Galois/Counter	B-Algorithm
Mode	I-Algorithm
.	O
</s>
<s>
As	O
the	O
backup	B-Protocol
server	O
can	O
not	O
access	O
the	O
backup	B-Protocol
data	O
without	O
the	O
matching	O
encryption	O
keys	O
,	O
it	O
can	O
even	O
be	O
an	O
untrusted	O
host	O
.	O
</s>
<s>
Data	O
retention	O
policy	O
can	O
be	O
defined	O
in	O
Proxmox	B-Application
Backup	I-Application
Server	I-Application
.	O
</s>
<s>
Removing	O
expired	O
data	O
is	O
done	O
in	O
two	O
phases	O
:	O
first	O
,	O
prune	O
removes	O
indices	O
of	O
the	O
backups	B-Protocol
which	O
are	O
no	O
longer	O
needed	O
,	O
and	O
then	O
garbage	B-General_Concept
collector	I-General_Concept
process	O
is	O
running	O
to	O
physically	O
delete	O
the	O
orphaned	O
data	O
chunks	O
.	O
</s>
