docs: explain the danger of IPAPPEND 1

Explain what the actual issue with IPAPPEND 1 is, and what the
constraints on using it really are.

Signed-off-by: Ferenc Wagner <wferi@niif.hu>
Signed-off-by: H. Peter Anvin <hpa@linux.intel.com>

diff --git a/doc/syslinux.txt b/doc/syslinux.txt
index 76cae24..5a93b90 100644 (file)
--- a/doc/syslinux.txt
+++ b/doc/syslinux.txt
@@ -163,11 +163,10 @@ IPAPPEND flag_val                 [PXELINUX only]
 
        ... based on the input from the DHCP/BOOTP or PXE boot server.
 
-       THE USE OF THIS OPTION IS NOT RECOMMENDED.  If you have to use
-       it, it is probably an indication that your network configuration
-       is broken.  Using just "ip=dhcp" on the kernel command line
-       is a preferrable option, or, better yet, run dhcpcd/dhclient,
-       from an initrd if necessary.
+       NOTE: The use of this option is no substitute for running a
+       DHCP client in the booted system.  Without regular renewals,
+       the lease acquired by the PXE BIOS will expire, making the
+       IP address available for reuse by the DHCP server.
 
        2: indicates that an option of the following format
        should be generated and added to the kernel command line: