Kernel Overview

You can use dmesg command to troubleshooting kernel errors. The dmesg command prints messages from the kernel ring buffer.

The following command, for example, presents kernel messages in a human-readable format:

dmesg --human --kernel

To examine kernel messages as you perform actions, such as reproducing a problem, in another terminal, you can run the command with the --follow option, which waits for new messages and prints them as they occur:

dmesg --human --kernel --follow

The kernel buffer is limited in memory size. As a result, the kernel cyclically overwrites the end of the information in the buffer from which dmesg pulls information. The systemd journal, however, saves the information from the buffer to a log file so that you can access older information.

To view it, run the following command:

journalctl -k

If required, you can check the modules that are loaded on your Photon OS machine by running the lsmod command. For example:

Module                  Size  Used by
vmw_vsock_vmci_transport    28672  1
vsock                  36864  2 vmw_vsock_vmci_transport
coretemp               16384  0
hwmon                  16384  1 coretemp
crc32c_intel           24576  0
hid_generic            16384  0
usbhid                 28672  0
hid                   106496  2 hid_generic,usbhid
xt_conntrack           16384  1
iptable_nat            16384  0
nf_conntrack_ipv4      16384  2
nf_defrag_ipv4         16384  1 nf_conntrack_ipv4
nf_nat_ipv4            16384  1 iptable_nat
nf_nat                 24576  1 nf_nat_ipv4
iptable_filter         16384  1
ip_tables              24576  2 iptable_filter,iptable_nat
Last modified March 5, 2021: setting up github actions (3f54ed117)