/root is full to the brim and I can't install new packages. My
/home has 8 times the space of my
/root, but pacman is set to install new packages on
/root. Is there a safe way that I can change where pacman permanently installs new packages?
No, there is no safe way to do this in the long term. From the manual:
Specify an alternative installation root (default is /). This should not be used as a way to install software into /usr/local instead of /usr. This option is used if you want to install a package on a temporary mounted partition that is "owned" by another system. NOTE: if database path or logfile are not specified on either the command line or in pacman.conf(5), their default location will be inside this root path.
This is not a permanent solution. You need to backup your data and resize your partitions.
You could also clean pacman's cache (
-Scc) to free up some space in the short term.