Mailing List Archive: PXE max boot image size?

PXE max boot image size?

Mar 20, 2002, 1:13 PM

Post #1 of 5 (2634 views)

Sorry if this is a FAQ, but what is the upper bound on the size of a
PXELINUX boot image, both via the kernel/initrd method and the memdisk
method? Is it the size of the initrd on the server (i.e., gzipped) that
matters or the size after uncompressing it?

Thanks,

Trey Harris
Morgan Stanley
Global UNIX Engineering, New York
Secretary, the System Administrators Guild (www.sage.org)

PXE max boot image size? [ In reply to ]

hpa at zytor

Mar 20, 2002, 2:54 PM

Post #2 of 5 (2544 views)

Permalink

Trey.Harris@morganstanley.com wrote:
> Sorry if this is a FAQ, but what is the upper bound on the size of a
> PXELINUX boot image, both via the kernel/initrd method and the memdisk
> method? Is it the size of the initrd on the server (i.e., gzipped) that
> matters or the size after uncompressing it?
>

PXELINUX doesn't limit the size of an initrd or memdisk; in practice, they
need to fit into memory uncompressed. If you're using a Linux kernel,
it needs to specifically fit into the "kernel" part of the memory space, which
is usually just under 1 GB.

-hpa

PXE max boot image size? [ In reply to ]

Trey.Harris at morganstanley

Mar 20, 2002, 3:01 PM

Post #3 of 5 (2626 views)

Permalink

Ah. So, short of the ~1GB limit, it's bounded by the size of the system
RAM, not anything on the NIC? That was my question--most of our systems
have 4GB RAM or more. Sounds like it won't be an issue, even if we tried
to ship an entire CD-ROM image--network bandwidth would be a problem far
earlier.

On Wed, 20 Mar 2002, H. Peter Anvin wrote:

> Trey.Harris@morganstanley.com wrote:
> > Sorry if this is a FAQ, but what is the upper bound on the size of a
> > PXELINUX boot image, both via the kernel/initrd method and the memdisk
> > method? Is it the size of the initrd on the server (i.e., gzipped) that
> > matters or the size after uncompressing it?
> >
>
> PXELINUX doesn't limit the size of an initrd or memdisk; in practice, they
> need to fit into memory uncompressed. If you're using a Linux kernel,
> it needs to specifically fit into the "kernel" part of the memory space, which
> is usually just under 1 GB.
>
> -hpa
>
>
>

PXE max boot image size? [ In reply to ]

hpa at zytor

Mar 20, 2002, 3:03 PM

Post #4 of 5 (2540 views)

Permalink

Trey.Harris@morganstanley.com wrote:
>
> Ah. So, short of the ~1GB limit, it's bounded by the size of the system
> RAM, not anything on the NIC? That was my question--most of our systems
> have 4GB RAM or more. Sounds like it won't be an issue, even if we tried
> to ship an entire CD-ROM image--network bandwidth would be a problem far
> earlier.
>

No other limit. MEMDISK supports up to 4 GB (obviously, you'll have no
memory left for the OS if you use that much.)

-hpa

PXE max boot image size? [ In reply to ]

hpa at zytor

Mar 21, 2002, 2:48 AM

Post #5 of 5 (2949 views)

Permalink

H. Peter Anvin wrote:
> Trey.Harris@morganstanley.com wrote:
>
>>Ah. So, short of the ~1GB limit, it's bounded by the size of the system
>>RAM, not anything on the NIC? That was my question--most of our systems
>>have 4GB RAM or more. Sounds like it won't be an issue, even if we tried
>>to ship an entire CD-ROM image--network bandwidth would be a problem far
>>earlier.
>
> No other limit. MEMDISK supports up to 4 GB (obviously, you'll have no
> memory left for the OS if you use that much.)
>

One more thing on this subject: some TFTP servers handle sequence number
wraparound incorrectly. Sequence numbers wrap around every 2^16 packets
== 32 MB. The latest versions of PXELINUX and tftp-hpa should handle
this correctly, but older versions might not.

-hpa