I set out two goals: 1) to monitor via a serial port (serial on
Linux to USB on Windows with the StarTech.com 1 Port FTDI USG to
RS232 Serial Null MOdem Adapter Cable -- puchased at Amazon), and
2) monitor xen boot-up via serial port.
I was able to plug in and monitor using PuTTY on Windows, but
when the initramfs kicked in, nothing appeared on my serial port.
I could see Grub, the EFI shell. So I disengaged framebuffer
support in my kernel (setting console display driver
support-->framebuffer to empty) and recompile, then I started
seeing the output of the initramfs.
My regular Linux kernel line (at https://pastebin.com/W3ASmFtv
for 30 days) is this:
echo 'Loading Linux x86_64-4.19.23-gentoo ...'
linux /kernel-genkernel-x86_64-4.19.23-gentoo
root=/dev/sda4 ro console=tty0
console=ttyS0,115200n8 showopts noquiet log_buf_len=10M print_fatal_signals=1 earlyprintk=vga,keep
debug loglevel=8
echo 'Loading initial ramdisk ...'
initrd /initramfs-genkernel-x86_64-4.19.23-gentoo
My xen kernel line is this:
multiboot /xen.gz
placeholder vga=gfx-1920x1080x16
com1=115200,8n1,pci
console=com1,vga console_timestamps
console_to_ring conring_size=64 log_buf_len=16M
loglvl=all guest_loglvl=all
sync_console=true
sched_debug iommu=verbose apic_verbosity=verbose ${xen_rm_opts}
echo 'Loading Linux x86_64-4.19.23-gentoo ...'
module /kernel-genkernel-x86_64-4.19.23-gentoo
placeholder root=/dev/sda4 ro softlevel=xen
video=vesa:off video=efifb:1024x768
xencons=xvc console=tty0
console=hvc0 showopts noquiet log_buf_len=10M print_fatal_signals=1 earlyprintk=xen,keep
debug loglevel=8
echo 'Loading initial ramdisk ...'
module --nounzip /initramfs-genkernel-x86_64-4.19.23-gentoo
Select portion of my /etc/default/grub (full file at
https://pastebin.com/Ctuug0xk for 30 days) are:
================== start =================
# Uncomment to disable graphical
terminal (grub-pc only)
# 3/3/19 jlpoole: uncommented
below; added "serial" as 2nd parameter
#
GRUB_TERMINAL="console serial"
#
# 3/3/19 jlpoole: added line
below because running
# grub-mkconfig -o
/boot/grub/grub.cfg
# caused:
# Warning: Requested serial
terminal but GRUB_SERIAL_COMMAND is unspecified. Default
parameters will be used.
#
GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8
--parity=no --stop=1"
...
# Uncomment if you don't want
GRUB to pass "root=UUID=xxx" parameter to kernel
# 3/3/19 jlpoole: uncommented
below
GRUB_DISABLE_LINUX_UUID=true
# Uncomment to disable
generation of recovery mode menu entries
# 3/3/19 jlpoole:
uncommented below
GRUB_DISABLE_RECOVERY=true
...
GRUB_CMDLINE_LINUX_XEN_REPLACE="softlevel=xen \
video=vesa:off video=efifb:1024x768
\
xencons=xvc console=tty0
console=hvc0 \
showopts noquiet log_buf_len=10M
print_fatal_signals=1 \
earlyprintk=xen,keep debug
loglevel=8 \
"
GRUB_GFXMODE=auto
GRUB_GFXPAYLOAD_LINUX="keep"
GRUB_TERMINAL_INPUT="console serial"
GRUB_TERMINAL_OUTPUT="gfxterm serial"
GRUB_CMDLINE_XEN=" \
vga=gfx-1920x1080x16 \
com1=115200,8n1,pci console=com1,vga
console_timestamps console_to_ring conring_size=64 \
log_buf_len=16M \
loglvl=all guest_loglvl=all
sync_console=true sched_debug iommu=verbose
apic_verbosity=verbose \
"zeta /home/jlpoole #
======================= end
======================
Observations:
- I found that if I go into edit
mode in Grub form the serial console running on Windows 7 using
PuTTY, things go screwy. I'm using 115200 baud. If I want to
edit grub at the commencement of a boot using the editor in
grub, I have to do so with the keyboard and screen attached to
the server.
- Under the current setup,
initramfs only shows up in the serial console, not on the screen
connected to the server
- I see some doubling up of
messages on the console before the initramfs output
- Sometimes the connection goes
dead, I am using an extension cord, 10 feet?, from the server to
my Windows box.
- The recent posting in this
newsgroup of PGNet Dev on 2/27/2019, 5:29 AM was essential to my
success, I was getting desperate, so I copied the values from
that email and voila... I had my first successful boot to
"login:" (Thank you PGNet DEV!!!)
- using debug causes two drop-in
shells where you have to type "exit" + enter to return to normal
processing
- I've posted another topic on
this forum entitled "Boot Sometimes Hangs At "masked EXTINT"
(Varies)" and I'm not certain my problem is the kernel stopping,
or my serial port. I'm pretty sure it's the kernel.
- I spent well over 20 hours to
get to this point
John
On 2/27/2019 3:50 AM, Enrique Sainz
Baixauli wrote:
Thanks PGNet Dev and Mr. Poole for your answers.
So, it seems that console=vga,com1 is not enough to show
the boot process output on screen and we need a serial cable
to debug, is that correct? If so, I will wait for Mr.
Poole's feedback. FWIW, I also tried console=vga (without
com1) and the screen was as blank as before.
However, I am concerned about the different versions of
"everything" we have, most importantly Xen. I am using 4.9
because that's what's being shipped with Ubuntu, but if
PGNet Dev's issue is the same as mine, the issue exists at
least in 4.9 and in 4.12. And I guess Mr. Poole is using
gentoo's stable xen package, which is 4.10.2 (
https://packages.gentoo.org/packages/app-emulation/xen).
What I mean is, has no one noticed this before or are we
all doing something wrong? Or did this issue come with a
kernel update instead of xen?
Again, thanks everyone for reading and adding whatever
info you may find useful.
Cheers!
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--
John Laurence Poole
1566 Court ST NE
Salem OR 97301-4241
707-812-1323 office
