So I followed this guide to create my (very first) tile server. While the server works and we are able to serve tiles, when zooming in tiles take a long time (30s) to render. I'm attempting to pre-render the tiles using the command below but I get the following error.
dogbert@info-osm-tile-serv:/var/www/html/osm$ render_list -f -a
debug: init_storage_backend: initialising file storage backend at: /var/lib/mod_tile
Rendering client
Starting 1 rendering threads
Rendering all tiles from zoom 0 to zoom 20
Rendering all tiles for zoom 0 from (0, 0) to (0, 0)
Rendering all tiles for zoom 1 from (0, 0) to (1, 1)
Rendering all tiles for zoom 2 from (0, 0) to (3, 3)
Rendering all tiles for zoom 3 from (0, 0) to (7, 7)
Rendering all tiles for zoom 4 from (0, 0) to (15, 15)
Rendering all tiles for zoom 5 from (0, 0) to (31, 31)
Rendering all tiles for zoom 6 from (0, 0) to (63, 63)
rendering failed with command 4, pausing.
render_list -m default -a -z 0 -Z 10