Re: From TFTP weaknesses to RAMdisk netboot

[Kent Snook <kent.snook@echostar.com>]

Pricop Ioan wrote:
> 
> --- Kent Snook <kent.snook@echostar.com> wrote:
> > We encountered similiar problems. Implemented the
> > following.
> >
> > First results in an automatic reboot upon tftp
> > timeouts, instead of
> > waiting for a key press ( we regularly reboot these
> > hosts remotely ).
> > Second reduces the tftp timeout to get hosts up and
> > running much faster.
> > ( We use ramdisks for all of our diskless hosts, so
> > images can run up to
> > 6-10 mb in size, at 5 seconds per packet tftp
> > timeout, could take 15
> > minutes or more to boot. Now less than a minute.)
> >
> ..........
> >
> > --
> > Kent
> >
> 
> Dear Kent,
> 
> Maybe you can help me with my problem. I am using
> EtherBoot to experiment with a diskless client. After
> a few hoops, I made it working from a NFS-root
> filesystem. Now I am experimenting with RAM-disks. I
> tried with a 9 MB fs and it seems to work. Then, I
> tried with a 96 MB fs. Of cause, I modified the
> /usr/src/linux-2.2.5/drivers/block/rd.c to be able to
> create ramdisks of 128 MB (have 196 MB on the client)
> and recompiled the kernel. I tested these, by creating
> a 128 MB RAMdisk and populating it with the fs I
> downsized at 96MB. It worked with a "chroot",
> exception the X part (only fvwm and Netscape). I
> obtained a 50 MB "rdImage.gz". But when I tried to
> make a NBI and boot it, all is well until it's
> tftp-ing the NBI. Than the rotator keeps spinning and
> spinning forever - i think, cause after 2.5 hours I
> stopped the process. Anyway, with "tcpdump" I
> estimated the 3.8 MB composed immage loading time (fs
> of 9 MB gzipped) and calculated the 51 MB one's - it
> must have been 1 min and 47 secs. What can be wrong?
> Can anyone tip me on some sites where I can find
> specific documentation on NBI use of ramdisks?
> 
> Thank you for at least reading this mail,
> 
> =====
> Ioan (John) NIKY Pricop
> Bucharest - ROMANIA
> pniky@yahoo.com
>

A 96MB image could take many hours to tftp to the client. Before I
changed the TFTP_TIMEOUT value, a 10MB image could take 30 minutes on a
GOOD day. Turn on block counting with etherboot to get a visual of which
block you are on. If you require a filesystem as large as you are trying
to load, I would recommend using nfs instead of a RAMDISK. We took the
RAMDISK route to free our diskless hosts from dependencies on other
hosts on our net.

We use make to run a Makefile which in turn executes shell commands and
calls shell scripts to create our images. Our largest image/filesystem
is around 10mB. I would recommend creating a filesystem that contains
only the binaries you actually require. Use ldd to determine the
libraries you need and eliminate the ones you don't need. Strip all
files (be carefull with any modules- don't use the --strip-all option
for these!!). 

Hope this helps.

-- 
Kent
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