From cda62db95d3d361bc15a7297355542b67524ef05 Mon Sep 17 00:00:00 2001
From: Randy Bush <randy@psg.com>
Date: Sat, 4 Jul 2020 14:33:40 -0700
Subject: [PATCH] from wiki

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 pages/SerialConsole.md | 203 +++++++++++++++++++++++++++++++++++++++++
 1 file changed, 203 insertions(+)
 create mode 100644 pages/SerialConsole.md

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+# Ubuntu Serial or USB Console
+
+## For systemd, (Xenial, Stretchm etc. try this recipe
+
+### Make desktop system into a server
+
+If you want to neuter your desktop install (all that may be available for xenial or stretch, t
+
+Be sure `/etc/network/interfaces` is properly configured and test it!
+
+Then 
+
+```
+# apt-get purge network-manager\*
+```
+
+### Tell systemd you want a text, not graphical, console
+
+The voodoo for telling systemd that you want a text console instead of X11 is:
+
+```
+# systemctl set-default multi-user.target
+```
+
+### /etc/default/grub
+
+Edit `/etc/default/grub` to have
+
+```
+GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,9600n8"
+...
+GRUB_TERMINAL=console
+GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
+```
+
+If you set `GRUB_TERMINAL` to `serial` instead of `console`, the GRUB boot dialog should show up on the serial console.
+
+You can toss glorp in to change the name of the ethers to good old ethN
+
+```
+GRUB_CMDLINE_LINUX="net.ifnames=0 biosdevname=0 console=tty0 console=ttyS0,9600n8"
+```
+
+And reconfigure grub
+
+```
+# update-grub
+```
+
+At this point you should reboot, because the GRUB configuration doesn't have much effect until the next boot.
+
+Sometimes the above is insufficient, as systemd needs to be further pacified.  Try the reboot first, but if that doesn't work:
+
+```
+cat > /lib/systemd/system/ttyS0.service << EOF
+[Unit]
+Description=Serial Console Service
+
+[Service]
+ExecStart=/sbin/getty -L 115200 ttyS0 vt102
+Restart=always
+
+[Install]
+WantedBy=multi-user.target
+EOF
+
+systemctl daemon-reload
+systemctl enable ttyS0
+systemctl start ttyS0
+```
+
+### Done
+
+systemd will automatically start a getty on the console if it thinks the console exists.  If there's no getty, it's probably because systemd doesn't think that's the console.  In wp's case, systemd was right about this: a serial port that doesn't exist probably is not the console.
+
+## For upstart-based systems
+
+### /etc/default/grub
+
+Hack a new /etc/default/grub, being sure to run update-grub
+
+```
+# If you change this file, run 'update-grub' afterwards to update
+# /boot/grub/grub.cfg.
+# For full documentation of the options in this file, see:
+#   info -f grub -n 'Simple configuration'
+
+GRUB_DEFAULT=0
+#GRUB_HIDDEN_TIMEOUT=0
+GRUB_HIDDEN_TIMEOUT_QUIET=true
+GRUB_TIMEOUT=6
+GRUB_DISTRIBUTOR=`lsb_release -i -s 2> /dev/null || echo Debian`
+GRUB_CMDLINE_LINUX_DEFAULT=""
+GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,9600n8"
+
+# Uncomment to enable BadRAM filtering, modify to suit your needs
+# This works with Linux (no patch required) and with any kernel that obtains
+# the memory map information from GRUB (GNU Mach, kernel of FreeBSD ...)
+#GRUB_BADRAM="0x01234567,0xfefefefe,0x89abcdef,0xefefefef"
+
+# Uncomment to disable graphical terminal (grub-pc only)
+#GRUB_TERMINAL=console
+
+# The resolution used on graphical terminal
+# note that you can use only modes which your graphic card supports via VBE
+# you can see them in real GRUB with the command `vbeinfo'
+#GRUB_GFXMODE=640x480
+
+# Uncomment if you don't want GRUB to pass "root=UUID=xxx" parameter to Linux
+#GRUB_DISABLE_LINUX_UUID=true
+
+# Uncomment to disable generation of recovery mode menu entries
+#GRUB_DISABLE_RECOVERY="true"
+
+# Uncomment to get a beep at grub start
+#GRUB_INIT_TUNE="480 440 1"
+
+GRUB_TERMINAL="console serial"
+GRUB_SERIAL_COMMAND="serial --speed=115200 --unit=0 --word=8 --parity=no --stop=1"
+```
+
+Be sure to run update-grub
+
+### /etc/init/ttyS0.conf
+
+Hack /etc/init/ttyS0.conf as follows"
+
+```
+# ttyS0 - getty
+
+start on stopped rc or RUNLEVEL=[12345]
+stop on RUNLEVEL=[!12345]
+
+respawn
+
+exec /sbin/getty -L 115200 ttyS0
+```
+
+For trusty, just try
+
+```
+start ttyS0
+```
+
+If you have an /etc/inittab, uncomment
+
+```
+T0:23:respawn:/sbin/getty -L ttyS0 115200 vt100
+```
+
+And you can kick off the getty without reboot
+
+```
+start ttyS0
+```
+
+------
+
+## For Non_Ganeti (Old)
+
+This is old.  See [The Official Ubuntu Hack](https://help.ubuntu.com/community/SerialConsoleHowto) for modern penguins.
+
+Assuming there is also a video card you want to support,  edit /boot/grub/grub.cfg to add
+
+```
+console=tty0 console=ttyS0,9600n8
+```
+
+as in
+
+```
+        linux   /boot/vmlinuz-3.5.0-40-generic root=UUID=11b8206e-6eed-4adf-83d8-e03e712d4c51 ro console=tty0 console=ttyS0,9600n8
+```
+
+If it is a USB console, it will be
+
+```
+console=tty0 console=ttyUSB0,9600n8
+```
+
+Now, next boot of the server should be visible on the serial (and video) console.
+
+To get a normal getty running, create /etc/event.d/ttyS0 with the following content:
+
+```
+# ttyS0 - getty
+#
+# This service maintains a getty on ttyS0 from the point the system is
+# started until it is shut down again.
+start on runlevel 2
+start on runlevel 3
+start on runlevel 4
+start on runlevel 5
+stop on runlevel 0
+stop on runlevel 1
+stop on runlevel 6
+respawn
+exec /sbin/getty -L 9600 ttyS0 vt102
+```
+
+Analogously for /etc/event.d/ttyUSB0.
+
+Of course, baud rate should be adjusted to taste.
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