[syslinux] RFC 3942 notice: PXELINUX, DHCP options 208-211

H. Peter Anvin hpa at zytor.com
Tue Jan 18 16:48:28 PST 2005

Dear friends,

In accordance with RFC 3942 I would like to submit the following DHCP 
options for official consideration.  These options are used by PXELINUX, 
which is part of the SYSLINUX distribution, and although exact usage 
count is impossible to determine, is widely held to be the most widely 
used method for booting Linux from a network.


Option 208: pxelinux.magic (string)
Must be set to F1:00:74:7E ( for PXELINUX to recognize any 
special DHCP options whatsoever.

Option 209: pxelinux.configfile (text)
Specifies the PXELINUX configuration file name.

Option 210: pxelinux.pathprefix (text)
Specifies the PXELINUX common path prefix, instead of deriving it from 
the boot file name. This almost certainly needs to end in whatever 
character the TFTP server OS uses as a pathname separator, e.g. slash 
(/) for Unix.

Option 211: pxelinux.reboottime (unsigned integer 32 bits)
Specifies, in seconds, the approximate time to wait before reboot in the 
event of TFTP failure. 0 means wait forever (in reality, it waits 
approximately 136 years.)


Out of these, option 208 is strictly use as a safety and is obviously 
not required if 209-211 become official assignments.

It is my belief that 209, 210 and 211 are of general interest and should 
be promoted to official.  In particular a more withspread use of 211 
would probably improve remote booting reliability by giving the server 
explicit control over the early boot failure policy.

Option 210 could arguably be considered redundant with option 17, but I 
personally feel they are distinct enough to warrant separate 
assignments.  In particular, 210 is more of a "current working 
directory" than a root image path.


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