[syslinux] Can USBstikA boot USBstkB ?!

[Gene Cumm]

On Sun, Dec 10, 2017 at 2:59 AM, eas lab <lab.eas at gmail.com> wrote:
> Gene Cumm wrote:-
>>TC64 still has ISOLINUX.  The basics are to use chain.c32 to boot
>>USB-B:p3 but syntax depends.  Ideally, it's a modern enough Syslinux
>>version that you can use the "guid" or "label" options to auto-detect
>>its location rather than "chain.c32 hdN M".  Hopefully your FS
>>label/GUID is unique
>
>  sdb3        Boot        Primary   ext4     [New486Xfce]      7593.79
> New486Xfce <- Label per cfdisk
> Useing existing working ISOLINUX entry as template:
>
> Since I will assume that the order of mounting / accessing files is:
> 1: KERNEL /boot/S3P3/vmlinuz-3.2.0-4-486
> 2: INITRD /boot/S3P3/initrd.img-3.2.0-4-486
> 3: <mount applicable root> ,
>  I'll put the new krnl & initrd, in their own dir in usbA: to avoid
> the possible problem of usbB not being readable. from usbA

So we're not booting USB-B but loading a kernel/initrd that's pointing
to USB-B.  This is a far far far more reliable approach.

> So minimally modifying a proven entry on usbA:isolinux.cfg gives:-
> LABEL S3:P3:rootUseLABEL

I'd KISS this (Keep It Simple) and make it like

  LABEL s3p3rt

It's typable with only letters/numbers and short.  Otoh, go "hog wild"
on the contents of MENU LABEL.  Feel free to put most any printable
character in there.

> MENU LABEL video args for S3:P3
> TEXT HELP
> Use proven Krn & initrd from S3P3 copied to own /boot/S3P3
> ENDTEXT
> KERNEL /boot/S3P3/vmlinuz-3.2.0-4-486
> INITRD /boot/S3P3/initrd.img-3.2.0-4-486
> APPEND root=LABEL=New486Xfce
>
> ==> OK ! usbA Boots the installation on usbBpartition3 !! Thanks.
>
> I previously postponed admitting the full problem, but

...  a concise clear problem statement goes a long way to getting
desired results.

> usbBpartition3 is problematic, and when booted from GRUB, I need to use:
>
>  linux /boot/vmlinuz-3.2.0-4-486
>     root=UUID=3169ee17-bdeb-41fa-984a-94badd02799a ro single
>
> where AFAIK "ro single" gives me recovery-mode and ROOT permission;

Read Only; SINGLE user mode.

> where the single VT-mode allows me to set some env. & call `startx`.
> I must have root-permission, since this Deb7 crap doesn't know 'sudo'.

Debian has sudo but likely doesn't install it by default taking the
more traditional model of using su.

https://packages.debian.org/stretch/sudo

There's nothing stopping you from booting run level 3/5, login on CLI,
su (Switch User) to root (default) then startx.

> The final goal will be using "video=vesa:ywrap,mtrr vga=788"
>  in isolinux; since these parameters are the only known way to get
>  the important app to use proper <font sizes>.
>
> When the good fonts show [only acheivable by booting DVD-rescue]
>   `cat /proc/cmdline` shows:---
> 'video=vesa:ywrap,mtrr vga=788 initrd=/install.386/gtk/initrd.gz
>    rescue/enable=true -- quiet
>       BOOT_IMAGE=/install.386/vmlinuz"
>
> indicating that "video=vesa:ywrap,mtrr vga=788" is needed by isolinux
> to get the essential good font.

Nope, ISOLINUX doesn't need this in any way.  This is stuff that you
need to put in your config to pass to your kernel.  Your kernel/initrd
uses it.

> So I first needed to confirm that usbA, which has a proven isolinux
> could boot usbBpartition3, which has the special app, that needs
> "video=vesa:ywrap,mtrr vga=788" via isolinux.
> -------------------------------------------------------------------------
> Searching the DVD, for how/where "video=vesa:ywrap,mtrr vga=788"
> is used by isolinux to launch the <graphics rescue mode> shows eg:-

It's not used by ISOLINUX but merely passed from ISOLINUX to the
kernel and the kernel/initrd uses it.

> label expertgui
>   menu label Graphical expert install
>   kernel /install.386/vmlinuz
>   append desktop=xfce priority=low video=vesa:ywrap,mtrr vga=788
> initrd=/install.386/gtk
> /initrd.gz --
> --------------
> So I'll try to use:--
>
> KERNEL /boot/S3P3/vmlinuz-3.2.0-4-486
> INITRD /boot/S3P3/initrd.img-3.2.0-4-486
> APPEND root=LABEL=New486Xfce video=vesa:ywrap,mtrr vga=788
> --------------------------------------------------------------------

Did you copy sdb3:install.386/gtk/initrd.gz to
sda?:boot/S3P3/initrd.img-3.2.0-4-486

> which is a DISASTER: failure by isolinux with NO indication WHY,
> is worse that programming a uProc in hex via a TTY in the 70s!

Errors are often obscured by a menu.  Get out of forcing use of the
menu and try again.  HOPEFULLY this is as simple as merely commenting
out a "UI menu.c32" line as "# UI menu.c32".

-- 
-Gene