As long as it's not the first system startup, on a headless machine with little in way of devices. Then you run the risk of generating a number without a seed.

As long as it's not the first system startup, on a headless machine with little in way of devices. Then you run the risk of generating a number without a seed. But the risk is low, since things like disk IO read times and other such will seed the generator unpredictable ways. Linux is smart enough to squirrel away some random on reboots so that it can properly seed the generator when it starts up again. On my system it looks like it's 512 bytes: $ wc -c /var/lib/urandom/random-seed 512 /var/lib/urandom/random-seed