Despite not all UNIX commands exist on the iPhone, as a first try it’s really nice to be able to navigate into the iPhone filesystem.
There is a mean to add additional commands by downloading the iphone-binkit.

This kit includes port to iPhone of common UNIX commands:

/bin:
chroot,dcgen,env,groups,login,nl,ps,setuidgid,shuf,sync,
uname,whoami,base64,cksum,dd,expand,head,logname,od,ptx,sh,
sleep,tac,unexpand,yes,basename,comm,df,expr,hostid,ls,osh,
pwd,sha1sum,sort,tail,uniq,bash,cp,dir,factor,hostname,md5sum,
paste,readlink,sha224sum,split,tee,unlink,cat,csh,dircolors,false,
join,mkdir,pathchk,rm,sha256sum,stat,test,uptime,chgrp,csplit,
dirname,fmt,kill,mkfifo,pinky,rmdir,sha384sum,stty,tr,users,chmod,
cut,ditto,fold,link,mknod,pr,sed,sha512sum,su,true,vdir,chown,date,
echo,install,ln,mv,printf,seq,shred ,sum,tsort,who

/sbin:
ifconfig, kextstat, kextunload, ping,route

/usr/bin:
awk, banner, crontab, curl, dropbear, grep,gzip,id,mesg,minicom,nc,nice,nohup,pico,printenv, python.bin,renice,sar,scp,srelay,tar,top,touch,tty,uname,vim,wc

/usr/sbin:
arp, cron, fdisk, iostat, netstat, sysctl, tcpdump, vipw.

You can then install what corresponds to your needs…

SFTP server, SSH Daemon, Apache, SQLlite, Python & Ruby are also available for the iPhone