r2 -d /bin/ls: Opens radare2 with file /bin/ls in debugger mode using the radare2 native debugger, but does not run the program. You’ll see a prompt (radare2) - all examples are from this prompt.
db flag: place a breakpoint at flag, where flag can be either an address or a function name
db - flag: remove the breakpoint at flag, where flag can be either an address or a function name
db: show list of breakpoint
dc: run the program
dr: Show registers state
drr: Show registers references (telescoping) (like peda)
ds: Step into instruction
dso: Step over instruction
dbt: Display backtrace
dm: Show memory maps
dk <signal>: Send KILL signal to child
ood: reopen in debug mode
ood arg1 arg2: reopen in debug mode with arg1 and arg2