acrnlog is a userland tool used to capture a ACRN hypervisor log. It runs as an SOS service at boot, capturing two kinds of logs:

  • log of the currently running hypervisor

  • log of last running hypervisor if it crashed and the logs remain.

Log files are saved in /tmp/acrnlog/, so the log files would be lost after a system reset.


The acrnlog tool is launched as a service at boot, and limited to supporting four 1MB log files by default. You can change this log file limitation temporarily or permanently.



display help


specify a polling interval (ms). Once buffer is empty, acrnlog stops and starts reading in specified interval. If an incomplete log warning is reported, please try with a smaller interval to get a complete log.


limit the size of each log file, in KB. 0 means no limitation.


specify the number of log files to keep, old files would be deleted.

Temporary Log File Changes

You can temporarily change the log file setting by following these steps:

  1. Stop the acrnlog service:

    # systemctl disable acrnlog
  2. Restart acrnlog, running in the background, and specify the new number of log files and their size (in MB). For example:

    # acrnlog -n 8 -s 4 &

You can use loglevel command in the hypervisor shell (not the Service OS shell) to query and change the hypervisor log level.

The mem_loglevel parameter controls the log to be saved using acrnlog, while the console_loglevel parameter controls the log output to the console. For example, in the hypervisor shell you can use these commands:

console_loglevel: 3, mem_loglevel: 5, npk_loglevel: 5
ACRN:\>loglevel 2 5
console_loglevel: 2, mem_loglevel: 5, npk_loglevel: 5

Permanent Log File Changes

You can also permanently change the log file settings by editing /usr/lib/systemd/system/acrnlog.service and use the -n and -s options on the ExecStart cmd, and restart the service. For example, acrnlog.service could have these parameters added:

ExecStart=/usr/bin/acrnlog -n 8 -s 4

and then restart the service with:

# systemctl daemon-reload
# systemctl restart acrnlog

Build and Install

Source code for the acrnlog tools is in the tools/acrnlog folder. Build and install the tools from source using:

# make
# make install

and if you changed the acrnlog.service file, install it using:

# cp acrnlog.service /usr/lib/systemd/system/