Merging OSM PBF files?

You can use osmium for merging:

osmium merge file1.osm file2.osm -o merged.osm.

Alternatively try osmosis:

osmosis --rx file1.osm --rx file2.osm --merge --wx merged.osm

Note that osmosis has a weird syntax and you need to specify the --merge commands n-1 times for merging n files.

On Ubuntu:

sudo apt-get install osmium-tool
osmium cat new-york.osm.pbf new-jersey.osm.pbf connecticut.osm.pbf -o ny-nj-ct.osm.pbf