How to re-enable serial console in ZNA64EE 3300

POSTED ON 7 July, 2017


The installation of zlbinstall_5.0.x.tgz triggers an update to grub configuration files resetting some system critical boot parameters which are necessary for serial console access through RS232 cable. If you update your Zevenet network appliance to Zevenet 5.0.x version then you will lose access through serial console cable after the update, follow the steps below to restore serial console access and avoid further issues in future updates.


Start a SSH session to the Zevenet Load Balancer appliance and backup grub settings files (to be restored in case of boot failure):

root@zlb# cp /boot/grub/grub.cfg /boot/grub/grub.cfg_backup
root@zlb# cp /etc/default/grub /etc/default/grub_backup

Edit grub default configuration file /etc/default/grub

root@zlb# vi /etc/default/grub

Change parameter GRUB_CMDLINE_LINUX=”” value to:

GRUB_CMDLINE_LINUX="console=tty0 console=ttyS0,19200n8"

Change the following parameters lines in order to redirect grub output to serial console port:

GRUB_SERIAL_COMMAND="serial --speed=19200 --unit=0 --word=8 --parity=no --stop=1"

Save changes and close file edition.

Now run the following command to update grub entries in /boot/grub/grub.cfg:

root@zlb# update-grub

Once it finishes, run the following command and check that text in bold appears console=tty0 console=ttyS0,19200n8, if so, you are ready to reboot the system and serial console output should now be working while system is booting.

root@zlb# cat /boot/grub/grub.cfg | grep console

terminal_input console

terminal_output console

linux /vmlinuz-3.16.0-4-amd64 root=/dev/sda2 ro console=tty0 console=ttyS0,19200n8 quiet

linux /vmlinuz-3.16.0-4-amd64 root=/dev/sda2 ro console=tty0 console=ttyS0,19200n8 quiet

linux /vmlinuz-3.16.0-4-amd64 root=/dev/sda2 ro single console=tty0 console=ttyS0,19200n8

If the text doesn’t appear in the previous output, do not reboot the unit and please contact with the Support Team in order to check with you what goes wrong by opening an issue in the official support portal Zevenet Central.

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Documentation under the terms of the GNU Free Documentation License.

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