Merge branch 'logging' into 'main'

doc: add section on logging to README

See merge request larswirzenius/vmadm!28

1 files changed, 16 insertions, 0 deletions

diff --git a/README.md b/README.md
index 930910d..cd5c2b3 100644
--- a/README.md
+++ b/README.md
@@ -116,6 +116,22 @@ In other words, if you specify any host keys, you get to do everything
 by hand. If you want to keep things easy, don't specify any host keys
 and let vmadm generate a host key and host certificate for a VM.
 
+## Logging
+
+To turn on logging, set the environment variable `VMADM_LOG`:
+
+~~~sh
+$ VMADM_LOG=vmadm::libvirt vmadm list
+ DEBUG vmadm::libvirt > connecting to libvirtd qemu:///system
+ DEBUG vmadm::libvirt > listing all domains
+$ 
+~~~
+
+vmadm uses the `env_logger` Rust library for logging, which is
+documented at <https://docs.rs/env_logger>. The environment variable
+can enable by log level, or by code module, or both. Setting it to
+`trace` gives the most detailed logging.
+
 # Using host certificates
 
 Host certificates allow you to access a newly created VM without