serial: T8375: use boot activation script to define a serial console on the CLI by c-po · Pull Request #5092 · vyos/vyos-1x

c-po · 2026-03-26T19:10:56Z

Change summary

Required during first-boot of a system. We have images form amd64 and arm64 CPUs which also tend to have different serial interfaces (ttyS vs. ttyAMA).

The images which are installed have the correct serial setting for GRUB (ttyS0 or ttyAMA0) and the activation script will probe the Kernel command-line. If a serial interface is defined, we will include it in the VyOS CLI configuration.

Types of changes

Bug fix (non-breaking change which fixes an issue)
New feature (non-breaking change which adds functionality)
Code style update (formatting, renaming)
Refactoring (no functional changes)
Migration from an old Vyatta component to vyos-1x, please link to related PR inside obsoleted component
Other (please describe):

Related Task(s)

https://vyos.dev/T8375

Related PR(s)

How to test / Smoketest result

TBD

Checklist:

I have read the CONTRIBUTING document
I have linked this PR to one or more Phabricator Task(s)
I have run the components SMOKETESTS if applicable
My commit headlines contain a valid Task id
My change requires a change to the documentation
I have updated the documentation accordingly

github-actions · 2026-03-26T19:11:09Z

👍
No issues in PR Title / Commit Title

zdc

Overall, it looks logical. Let's try to polish it, I think.

I think, if we use only one way to note the console, it will be less messy in the code: console_type + console_num or console_device.
There is a mix-up between str and None arguments in functions and their calls, which should work fine generally. But it may also end up with unexpected surprises in the long term, when someone will update calls. I would prefer to unify all calls to a single type. Also, we may consider using just the explicit defaults argument: str = '' more for "cleanup" operations to keep the mistake risk surface purely inside functions.

c-po · 2026-03-31T15:14:39Z

Smoketests are failing due to unmerged vyos/vyos-build#1152

src/migration-scripts/system/31-to-32

python/vyos/flavor.py

smoketest/scripts/cli/test_system_console.py

src/activation-scripts/05-serial_console.py

python/vyos/system/grub.py

sever-sever

Add console parameters based on architecture
At least we see the login/password for the git ARM runner

DEBUG - Welcome to VyOS - vyos ttyAMA0
DEBUG - 
DEBUG - vyos login: vyos
DEBUG - vyos
DEBUG - Password: vyos
DEBUG - 
DEBUG - Welcome to VyOS!
DEBUG - 
DEBUG -    ┌── ┐
DEBUG -    . VyOS 999.202604030943
DEBUG -    └ ──┘  current
DEBUG - 
DEBUG -  * Documentation:  https://docs.vyos.io/en/latest
DEBUG -  * Project news:   https://blog.vyos.io/
DEBUG -  * Bug reports:    https://vyos.dev/
DEBUG - 
DEBUG - You can change this banner using "set system login banner post-login" command.
DEBUG - 
DEBUG - VyOS is a free software distribution that includes multiple components,
DEBUG - you can check individual component licenses under /usr/share/doc/*/copyright
DEBUG - 
DEBUG - ---
DEBUG - WARNING: This VyOS system is not a stable long-term support version and
DEBUG -          is not intended for production use.
DEBUG - 
 INFO - Logged in!
DEBUG - vyos@vyos:~$ if sudo grep -rq "BEGIN PRIVATE KEY" /var/lib/shim-signed/mok; then echo Found private key - bailing out; exit 1; fi
DEBUG - if sudo grep -rq "BEGIN PRIVATE KEY" /var/lib/shim-signed/mok; then 
 echo Found private key - bailing out; exit 1; fi
 INFO - Starting installer
DEBUG - vyos@vyos:~$ install image
DEBUG - install image
DEBUG - Welcome to VyOS installation!
DEBUG - This command will install VyOS to your permanent storage.
DEBUG - Would you like to continue?y
DEBUG -  [y/N] y
DEBUG - What would you like to name this image? (Default: 999.202604030943)
DEBUG - 
DEBUG - Please enter a password for the "vyos" user: vyos
DEBUG - 
DEBUG - 
DEBUG - WARNING: Default password used. Consider changing it on next login.
DEBUG - 
DEBUG - Please confirm password for the "vyos" user: vyos
DEBUG - 
DEBUG - What console should be used by default? (K: KVM, S: Serial)? (DefauS
DEBUG - lt: A) S
DEBUG - Invalid value, try again.
ERROR - Timeout waiting for VyOS system
ERROR - Traceback (most recent call last):
  File "/__w/vyos-build-arm64/vyos-build-arm64/vyos-build/scripts/check-qemu-install", line 692, in <module>
    c.expect('\nWhich one should be used for installation?.*')
  File "/usr/lib/python3/dist-packages/pexpect/spawnbase.py", line 343, in expect
    return self.expect_list(compiled_pattern_list,
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/pexpect/spawnbase.py", line 372, in expect_list
    return exp.expect_loop(timeout)
           ^^^^^^^^^^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/pexpect/expect.py", line 181, in expect_loop
    return self.timeout(e)
           ^^^^^^^^^^^^^^^
  File "/usr/lib/python3/dist-packages/pexpect/expect.py", line 144, in timeout
    raise exc
pexpect.exceptions.TIMEOUT: Timeout exceeded.

jestabro

I see one issue here: the setting added to the config file during live boot (say, ttyS0) remains after the first boot into the installed image. Consequently, if a user chooses K(VM) during image install, that is correctly written to the grub vars for the reboot into the installed image; however, during that reboot, the system_console config script will re-write the config entry to the grub vars. A subsequent reboot will replace the choice of tty with ttyS.

c-po · 2026-04-06T08:27:42Z

I see one issue here: the setting added to the config file during live boot (say, ttyS0) remains after the first boot into the installed image. Consequently, if a user chooses K(VM) during image install, that is correctly written to the grub vars for the reboot into the installed image; however, during that reboot, the system_console config script will re-write the config entry to the grub vars. A subsequent reboot will replace the choice of tty with ttyS.

The issue has been corrected. Thanks for testing this interesting combination.

jestabro

The issue (mentioned above) with overwriting grub vars after installation has been resolved. The necessary tools to define a serial console on live-boot are in place.

zdc

The logic looks mainly solid. I have only a few questions and suggestions to clarify.

interface-definitions/system_console.xml.in

python/vyos/utils/kernel.py

zdc · 2026-04-09T12:31:53Z

python/vyos/utils/kernel.py

+    import re
+    from vyos.utils.file import read_file
+    CMDLINE_CONSOLE_RE = re.compile(
+        r'(?:^|\s)console=(?P<device>tty(?:S|AMA)\d+),(?P<speed>\d+)(?=\s|$)'


I'm not sure if this is possible, after this change, but to clarify: is speed always presented in the cmdline? Can there be totally no scenarios in which it is missing?

I'm just thinking about corner cases when, for instance, in PXE boot, users have a full control over the cmdline and can set whatever they want there.

If our image is used console speed is always present and defaulted to 115200 baud.

python/vyos/flavor.py

zdc · 2026-04-09T13:03:25Z

src/conf_mode/system_console.py


-    speed = console['device']['ttyS0']['speed']
-    grub_util.update_console_speed(speed)
+        if not use_serial_console:


Why a dedicated variable and not simply else:?

This is needed b/c of multiple serial console support, but only one is allowed to carry the kernel CLI option due to Kernel constraints.

If the code would look like:

if 'kernel' in device_config: # get console type ("ttyS" or "ttyAMA") from device (e.g. "ttyS0") console_type = device.rstrip('0123456789') console_num = device[len(console_type):] grub_util.update_serial_console(console_type, console_num, device_config['speed']) use_serial_console = True else: grub_util.update_serial_console(*default_tty_console)

And I would have:

set system console device ttyS0 kernel set system console device ttyS1

The GRUB console would be set to serial first (if-branch is true), but on the second iteration for ttyS1, there is no kernel parameter (else path) and the GRUB console would be switched back to tty0 defined by default_tty_console.

src/conf_mode/system_console.py

zdc · 2026-04-09T13:16:45Z

src/op_mode/image_installer.py

 # default boot variables
 DEFAULT_BOOT_VARS: dict[str, str] = {
    'timeout': '5',
    'console_type': 'tty',


It is not clear why there is no flavor_sercon_type here.

Yes, it is overwritten later during installation anyway, but this creates an inconsistency.

flavor_sercon_type is never used in GRUB - its a variable mapped later to a GRUB variable.

src/op_mode/image_installer.py

zdc · 2026-04-09T13:38:16Z

src/activation-scripts/05-serial_console.py

+    if not is_live_boot():
+        return


Nothing needs to be changed here, but if we use this condition, then we must also update all release flavors with a serial console to have a non-default config.boot file with a serial console inside (check kvm as an example of such a flavor). Otherwise, they will be locked out of the console right after boot.

KVM should fallback to tty0, but yes - we need to look into the flavor files as kvm indeed contains some "special"

# GRUB console settings [boot_settings] console_type = "ttyS" console_num = '0' console_speed = "115200"

Which by coincidence matches to the amd64 settings and should be properly consolidated

For the sake of nice grep lines and refactoring we have an unspoken - unwritten rule considered as folklore to have imports one per line. This helped in the past with refactorings.

Clearly indicate during startup what happens. When we see "system" on the CLI, infact we ran the activation scripts, thus the rename.

…on the CLI Required during first-boot of a system. We have images form amd64 and arm64 CPUs which also tend to have different serial interfaces (ttyS vs. ttyAMA). The images which are installed have the correct serial setting for GRUB (ttyS0 or ttyAMA0) and the activation script will probe the Kernel command-line. If a serial interface is defined, we will include it in the VyOS CLI configuration.

Previously, VyOS hardcoded the kernel boot log console to either ttyS0 or tty0, with no post-install CLI method to change it (manual GRUB edits were required). This commit adds a new CLI node: system console device <name> kernel When set, the selected serial console is used as the kernel boot console. When removed, the kernel boot console falls back to tty0.

github-actions · 2026-04-09T20:36:15Z

CI integration ❌ failed!

Details

CI logs

CLI Smoketests 👍 passed
CLI Smoketests (interfaces only) 👍 passed
Config tests 👍 passed
RAID1 tests 👍 passed
CLI Smoketests VPP ❌ failed
Config tests VPP 👍 passed
TPM tests ❌ failed

github-actions bot assigned c-po Mar 26, 2026

github-actions bot added the current label Mar 26, 2026

zdc requested changes Mar 27, 2026

View reviewed changes

c-po force-pushed the kernel-serial-activation branch 2 times, most recently from ed11d93 to 31f0e14 Compare March 31, 2026 13:02

c-po requested a review from zdc March 31, 2026 13:05

c-po marked this pull request as ready for review March 31, 2026 13:07

c-po mentioned this pull request Mar 31, 2026

flavor: T8375: add flavor.json during build into resulting image vyos/vyos-build#1152

Merged

11 tasks

c-po marked this pull request as draft March 31, 2026 13:13

c-po force-pushed the kernel-serial-activation branch 2 times, most recently from d1d817b to bd95a69 Compare March 31, 2026 14:59

c-po requested review from dmbaturin, jestabro and sever-sever March 31, 2026 15:08

c-po marked this pull request as ready for review March 31, 2026 15:08

c-po marked this pull request as draft March 31, 2026 15:15

c-po marked this pull request as ready for review April 2, 2026 20:49

c-po force-pushed the kernel-serial-activation branch from bd95a69 to 28c3206 Compare April 2, 2026 21:23