GDB

gdb ./programtodebug

Display, investigation

List source code:

If debugging symbols are present, you can use layout src.
Otherwise, layout asm
List from line x to y: l x,y

Address spaces

Mapped address spaces: info proc map
List functions and their address: info functions
Info on registers: info r

Show values:

p xxx. For example p $edi.
Specify /x for hex value, /t for binary, /d for unsigned int: print /x value
Display memory: x/60x addr where 60 is the length you want to display and x is the format (hex)

Show the stack:

bt
p $sp

Disassemble:

disassemble funcname

Searching:

searchmem hex start end

gdb-peda$ searchmem 0x4141 0x406000 0x427000 
Searching for '0x4141' in range: 0x406000 - 0x427000
Not found

Running, breaks etc

run $(perl -e 'print "A"x80)
Breakpoint. b line
To set a variable: set var=value
Get the type of a variable: whatis var

(gdb) whatis f
type = struct fp *

Step through an instruction: si
next

Little Endianness

Say you write "\x55\x55\x51\xa9" to 0x5555555592f0. Then you get:

0x5555555592f0:	0xa9515555

Core dump

To enable: uclimit -c unlimited

Load it: ./gdb prog core
Dump memory: objdump -s core