Ulimit
A single user who starts too many processes can make a system unusable for everyone else. A fork bomb -- a denial of service attack in which a process continually replicates itself until available resources are depleted -- is a worst case of this. To see the limits associate with your login, use the command ulimit -a. If you're using a regular user account, you will likely see something like this: $ ulimit -a core file size (blocks, -c) 0 data seg size (kbytes, -d) unlimited scheduling priority (-e) 0 file size (blocks, -f) unlimited pending signals (-i) 32767 max locked memory (kbytes, -l) 32 max memory size (kbytes, -m) unlimited open files (-n) 1024 pipe size (512 bytes, -p) 8 POSIX message queues (bytes, -q) 819200 real-time priority (-r) 0 stack size (kbytes, -s) 10240 cpu time (seconds, -t) unlimited max user processes ...