FORKBOMB(8)FORKBOMB(8)NAMEforkbomb - eat system resources
SYNOPSISforkbomb [options]
AUTHOR
This program and manual page was written by Radim Kolar hsn@netmag.cz,
for fun (but may be used for serious tasks).
DESCRIPTIONforkbomb is a simple resource hog program.
OPTIONS
The programs follow the usual GNU command line syntax, with long
options starting with two dashes (`-'). A summary of options are
included below.
-?, -h, --help
Show summary of options.
-v, --version
Show version of program.
--runasroot
Allows running with euid==0.
--nosafetyalarm, --infinite
Run for infinite time.
-c, --cpuhang
Eat CPU time. If -M is also used, write to allocated memory
instead of running infinite loop.
-f, --forkbomb
Fork infinite number of self copies.
-z. --zombie
Lets go to House of Dead. You can not bring bombs there.
-m, --allocmemory
Allocate all available memory.
-M, --touchmemory
Write to every page in allocated memory. Implies -m.
-t, --maxtime <sec>
Set maximum execution time.
-l, --memorylimit <MB>
Set memory allocation limit per process.
-i, --incpages <num>
Allocate memory in groups of num pages.
--quit Don't wait for safety alarm expiration (useful only with -m/-M
option for realloc() benchmarking)
EXIT STATUS
0 - your system has survived.
1 - Insufficient RTFM detected.
CLASSICS FORKBOMBforkbomb-f
Linux 2.4
crash. Can not switch virtual console, can not ping, death.
Linux 2.6
do not crash but runs very slowly.
FreeBSD 5.2
Excellent result, runs with only small slowdown.
FreeBSD 5.4
allocates too much wired memory and that hangs the system. Hang
is not that good as in Linux 2.4, because you can switch virtual
consoles.
PLAIN REALLOC RESULTSforkbomb-m -l 32 -i 256 --quit
Linux 2.4, 2.6
I have tested then only with glibc 2.3.2 and results are excel‐
lent. Both finished test with instantly with 0.00 CPU time.
FreeBSD 5.2
The realloc() has several serious problems. First problem is
that realloc is really slow, It needs 12 seconds to run this
test. It looks like it unnecessary copies data on reallocation.
Second problem is if you allocate more than -l 18 MB of memory,
malloc eats about 3 times more memory from system than needed.
Maybe this have something to do with size of malloc cache size
(default 16 pages). FreeBSD people should really look at their
libc/stdlib/malloc.c
REALLOC WITH TOUCHforkbomb-l 32 -i 256 -M --quit
Linux 2.4, 2.6
Linux is also super fast there, test run is 0.3 sec. Linux allo‐
cates bigger memory blocks directly from mmap and uses mremap
for resizing. There is no need for copying data around.
FreeBSD 5.2
FreeBSD runs for 9.9 seconds which is FASTER that without touch‐
ing memory at all.
HUNGRY FORKBOMBSforkbomb-f -c
Linux 2.4
dead.
Linux 2.6
ls command takes between 100 to 200 seconds. System load was
840.
FreeBSD 5.2
ls command takes 70 seconds to execute. System load was 800.
TODO
Incorporate user feedback.
COPYING
Forkbomb program and this manual page are both public domain.
13 May 2005 FORKBOMB(8)
