Alpine Linux - User contributions [en]

Enable Serial Console on Boot

2019-09-05T06:03:20Z

Chris: /* Add your serial console to the trusted local terminal list */

== How to Enable the Serial Console on Boot (1.10.x)==

When using syslinux to boot, you'll need to modify the syslinux.cfg file in the root directory of the boot device. If using a disk-based Alpine, modify the /boot/extlinux.cfg file.

Add the following:
* <tt>serial 0 9600</tt>
* add <tt>console=ttyS0,9600</tt> to the <tt>append</tt> parameter
* optionally, remove <tt>quiet</tt> from the <tt>append </tt> parameter

=== Example syslinux.cfg ===

<pre>
serial 0 9600
timeout 20
prompt 1
default grsec
label grsec
kernel /boot/grsec
append initrd=/boot/grsec.gz alpine_dev=sda1:vfat modules=sd-mod,usb-storage console=ttyS0,9600
</pre>

== extlinux.conf (3.0+)==

The /etc/update-extlinux.conf is read by the update-extlinux utility.

To do so, change the default entry:
<pre>default_kernel_opts="quiet"</pre>
to read like this:
<pre>default_kernel_opts="console=ttyS0,9600 quiet"</pre>

Set the serial port and baud rate to match the default_kernel_opts line above:
<pre>serial_port=0
serial_baud=9600</pre>

=== Xen ===

Notice, if you want to use this for a Xen VM,
you need to configure the speed at '''115200''' bps and enable the
<pre>serial="pty"</pre>
setting in the VM config file.

----

Xen can be configured to use and log to a serial console by editing /etc/update-extlinux.conf to include the following lines:
<pre>
default_kernel_opts="console=hvc0 earlyprintk=xen nomodeset"
xen_opts="dom0_mem=256M com1=115200,8n1 console=com1"
</pre>

See the [http://wiki.xen.org/wiki/Xen_Serial_Console Xen wiki] for more details.

=== Example /boot/extlinux.conf ===

This is a complete file, written by the update-extlinux command.

<pre>
DEFAULT menu.c32
PROMPT 0
MENU TITLE Alpine/Linux Boot Menu
MENU AUTOBOOT Alpine will be booted automatically in # seconds.
SERIAL 0 9600
TIMEOUT 100
LABEL grsec
MENU DEFAULT
MENU LABEL Linux 3.10.33-0-grsec
LINUX vmlinuz-3.10.33-0-grsec
INITRD initramfs-3.10.33-0-grsec
APPEND root=UUID=re-mov-ed-uu-id modules=sd-mod,usb-storage,ext4 console=ttyS0,9600

MENU SEPARATOR
</pre>

Please: adjust the tty speed to 115200 if needed (Xen!!).

The timeout is given in centiseconds, so this would be a 10 second timeout.

If the file is read by pygrub, the same value is interpreted as seconds, resulting in a 100s bootup delay per VM.

== Enabling a login console ==

This is done in /etc/inittab. There is commented entry for ttyS0. Just enable it.
<pre>
# Put a getty on the serial port
ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt100
</pre>

To start the getty, restart init:
<pre>
kill -HUP 1
</pre>

== Enabling two consoles during boot ==

It's possible to output to both the serial and vga console during the system boot.

<PRE>
append "quiet console=ttyS0,9600 console=tty0"
</PRE>

Not known how to do the same thing in the extlinux menu.
You might find a starting point in this thread: http://patchwork.openembedded.org/patch/45175/

== Add your serial console to the trusted local terminal list ==
If you face the problem that the login prompt always refuses your password when you use serial console, you missed this entry.

Add this to the <tt>/etc/securetty</tt> file:
<PRE>
ttyS0
</PRE>

[[Category:Booting]]
[[Category:Installation]]

Enable Serial Console on Boot

2019-09-05T06:02:44Z

Chris: /* Enabling two consoles during boot */

== How to Enable the Serial Console on Boot (1.10.x)==

When using syslinux to boot, you'll need to modify the syslinux.cfg file in the root directory of the boot device. If using a disk-based Alpine, modify the /boot/extlinux.cfg file.

Add the following:
* <tt>serial 0 9600</tt>
* add <tt>console=ttyS0,9600</tt> to the <tt>append</tt> parameter
* optionally, remove <tt>quiet</tt> from the <tt>append </tt> parameter

=== Example syslinux.cfg ===

<pre>
serial 0 9600
timeout 20
prompt 1
default grsec
label grsec
kernel /boot/grsec
append initrd=/boot/grsec.gz alpine_dev=sda1:vfat modules=sd-mod,usb-storage console=ttyS0,9600
</pre>

== extlinux.conf (3.0+)==

The /etc/update-extlinux.conf is read by the update-extlinux utility.

To do so, change the default entry:
<pre>default_kernel_opts="quiet"</pre>
to read like this:
<pre>default_kernel_opts="console=ttyS0,9600 quiet"</pre>

Set the serial port and baud rate to match the default_kernel_opts line above:
<pre>serial_port=0
serial_baud=9600</pre>

=== Xen ===

Notice, if you want to use this for a Xen VM,
you need to configure the speed at '''115200''' bps and enable the
<pre>serial="pty"</pre>
setting in the VM config file.

----

Xen can be configured to use and log to a serial console by editing /etc/update-extlinux.conf to include the following lines:
<pre>
default_kernel_opts="console=hvc0 earlyprintk=xen nomodeset"
xen_opts="dom0_mem=256M com1=115200,8n1 console=com1"
</pre>

See the [http://wiki.xen.org/wiki/Xen_Serial_Console Xen wiki] for more details.

=== Example /boot/extlinux.conf ===

This is a complete file, written by the update-extlinux command.

<pre>
DEFAULT menu.c32
PROMPT 0
MENU TITLE Alpine/Linux Boot Menu
MENU AUTOBOOT Alpine will be booted automatically in # seconds.
SERIAL 0 9600
TIMEOUT 100
LABEL grsec
MENU DEFAULT
MENU LABEL Linux 3.10.33-0-grsec
LINUX vmlinuz-3.10.33-0-grsec
INITRD initramfs-3.10.33-0-grsec
APPEND root=UUID=re-mov-ed-uu-id modules=sd-mod,usb-storage,ext4 console=ttyS0,9600

MENU SEPARATOR
</pre>

Please: adjust the tty speed to 115200 if needed (Xen!!).

The timeout is given in centiseconds, so this would be a 10 second timeout.

If the file is read by pygrub, the same value is interpreted as seconds, resulting in a 100s bootup delay per VM.

== Enabling a login console ==

This is done in /etc/inittab. There is commented entry for ttyS0. Just enable it.
<pre>
# Put a getty on the serial port
ttyS0::respawn:/sbin/getty -L ttyS0 115200 vt100
</pre>

To start the getty, restart init:
<pre>
kill -HUP 1
</pre>

== Enabling two consoles during boot ==

It's possible to output to both the serial and vga console during the system boot.

<PRE>
append "quiet console=ttyS0,9600 console=tty0"
</PRE>

Not known how to do the same thing in the extlinux menu.
You might find a starting point in this thread: http://patchwork.openembedded.org/patch/45175/

== Add your serial console to the trusted local terminal list ==
If you face the problem that you see the login prompt always refuses the password when you use serial console, you missed this entry.

Add this to the <tt>/etc/securetty</tt> file:
<PRE>
ttyS0
</PRE>

[[Category:Booting]]
[[Category:Installation]]