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.


-h display help
-t 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.
-s limit the size of each log file, in KB. 0 means no limitation.
-n 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/