New in libguestfs: virt-log

In libguestfs ≥ 1.27.17, there’s a new tool called virt-log for displaying the log files from a disk image or virtual machine:

$ virt-log -a disk.img | less

Previously you could write:

$ virt-cat -a disk.img /var/log/messages

That worked for some Linux guests, but several things happened:

• The binary systemd journal
• The command above doesn’t work on Debian guests (you need to use /var/log/syslog)
• Windows uses the Windows Event Log

Virt-log is designed to do the right thing automatically (although at the moment Windows support is not finished). In particular it will automatically decode and display the systemd journal, and it knows the different locations that some Linux distros store their plain text log files.

Journal support in libguestfs

New in libguestfs ≥ 1.23.11 is support for reading the systemd journal from a guest.

The support is rudimentary at the moment. It would be nice to have a guestfish journal command for easy browsing of the journal (somewhat like journalctl), but we’re not there yet.

You can use journalctl from guestfish (this is true even without the journal APIs that I just added), but it involves downloading the whole journal first so it’s rather slow:

><fs> copy-out /var/log/journal /tmp
><fs> ! journalctl -D /tmp/journal