Setup the serial configuration. Boot the VM. Then run the following to turn the unix socket into a terminal:

socat UNIX-CONNECT:/tmp/com1 PTY,link=/tmp/com1-pty

The above should block for the entire time of the conversation. If it doesn’t, there’s an issue. Fix it!

Then run a terminal program to talk with it:

screen /tmp/com1-pty

As an alternative to using screen, you can use the following in place of socat and screen above:

socat UNIX-CONNECT:/tmp/com1 STDIO,raw,echo=0

There are some places even root can’t get to. One such place is a FUSE mounted volume. I found this out when trying to access an sshfs mounted directory as root and got permission denied.

To get around this, do the following (which I learnt by asking about it on serverfault):

1. Add user_allow_other to /etc/fuse.conf
2. Run sshfs (or any other FUSE mounting command) with -o allow_root option.

Here are a few tricks to programatically find your public IP address:

curl -s http://jsonip.com | sed 's/.*"ip":"\([^"]\+\)".*/\1\n/'
curl -s http://ipinfo.io

A little ghostscript trick to merge multiple PDF files into one:

gs -q -sPAPERSIZE=letter -dNOPAUSE -dBATCH -sDEVICE=pdfwrite \
   -sOutputFile=out.pdf in1.pdf in2.pdf in3.pdf ...