Use fallocate -l 1G filename to quickly create a 1GB file; use dd if=/dev/zero of=filename bs=1M count=1024 for zero-filled compatibility.

To create a file of specified size in Linux, use `dd` or `fallocate`. For example: 1. `fallocate -l 1G filename` quickly allocates space. 2. `dd if=/dev/zero of=filename bs=1M count=1024` creates a 1GB file with zero data. Use `fallocate` for speed, `dd` for compatibility.