Capture Kernel Boot Messages in the Journal

By default Clear Linux OS does not capture kernel boot messages in the journal logs, where they’re reported as “Missed” messages. This design decision was made to provide a faster boot performance. On the other hand, if you wish to see the messages, follow this guide.

Here’s an example a journal log with “Missed” messages:

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-- Reboot --
Apr 10 19:55:43 kernel systemd-journald[300]: Journal started
Apr 10 19:55:43 kernel systemd-journald[300]: Runtime Journal (/run/log/journal/d01862ca79d1064ea379cd715cfdd53a) is 5.8M, max 47.0M, 41.1M free.
Apr 10 19:55:43 kernel systemd-journald[300]: Missed 2233 kernel messages
Apr 10 19:55:43 kernel systemd[1]: Started Journal Service.

Prerequisites

  • systemd-journald version 245 and higher

Enable journaling of kernel boot messages

  1. Open a terminal window.

  2. Create a base journald configuration file.

    sudo mkdir -p /etc/systemd/journald.conf.d
sudo cp /usr/lib/systemd/journald.conf.d/clear.conf /etc/systemd/journald.conf.d/

  3. Append BootKMsg=true to it.

    echo "BootKMsg=true" | sudo tee -a /etc/systemd/journald.conf.d/clear.conf

  4. Reboot.

Tip

If you need to increase the kernel buffer length (for example, 1M), do this:

sudo mkdir -p /etc/kernel/cmdline.d/
echo "log_buf_len=1M" | sudo tee /etc/kernel/cmdline.d/log_buf_len.conf
sudo clr-boot-manager update

Alternative

An alternative is to use dmesg.

sudo dmesg