mid 1960 ’ s - Multics - proposed by AT&T, Honeywell, GE & MIT; funded by DARPA Thompson & Ritchie create Unix 1978 to 84 - Bill Joy & Chuck Haley (Berkeley U.) create BSD Unix Unix Wars I - BSD 4.2 versus System V Unix Wars II - SVR4 versus OSF ISO Standard - POSIX Linus Torvalds creates Linux

BSD Mach System V HP-UXAIX OSF/1 SunOS Solaris NeXTStep Free BSD OS X Linux

Authentication Admin File Systems Network-related Audit

UID /etc/passwd UserName :*: UID : GID : FullName : UserDir : UserShell entry: GID passwords encrypted via crypt() salt 16-bits ID reserved ID 0 is root 16 or 32 bits /etc/group stores local groups wheel group for system administrators

Standard Users root - superuser account daemon - executes as background process - handles system events such as print spooling lp - print server process guest - generic visitor account nobody - default user for unprivileged access - user owns no files mail - system account for processing sshd - for running secure shell tasks www - for running a web server

shell commands command line interface Born (sh), c-shell (csh), tc-shell (tcsh) ls -- list directory information cd -- set current directory pwd -- display current directory cat -- display contents of textfile whoami -- display current user su -- log in as a different user (will be prompted for password) man -- give help on command sudo -- execute a single command as root (must specify password)

ufs ffs  original Unix File System  first tree-structured directory system  Fast File System  allows longer file names (255 chars rather than 14)  supports symbolic links inodes  separate inode (index node) per file/directory  an inode has an address (index) but no name  each inode resides on the disk  contents: address of associated item (file/directory) item type item size (in bytes) time of last inode modification time of last modification of item (mtime) time of last item access (atime) reference count (number of names for this inode) item ’ s UID item ’ s primary GID directory ...consists of a list of pairs: name - inode index item ’ s mode bits (permissions)

standard directory entries shell commands. refers to this directory ’ s inode.. refers to inode of the parent of this directory cp -- copy (duplicate) file mv -- move file from one directory to another mkdir -- create new directory ln -- create new link (use -s flag for symbolic link) rm -- remove one name rmdir -- log in as a different user (will be prompted for password) chown -- change owner of file/directory chmod -- change mode (permissions) for a file umask -- set default mode (permissions) for this user

- rwx r-x --- t - file d directory c character device (tty, printer) b block device (disk, CD) l symbolic link s socket ownergroupworld Mode: sticky bit set GID set UID read (owner) write (owner) execute (owner) r read w write x execute s set (in place of x) Example t “ sticky ” bit

TCP Wrappers host-based firewalls a common way to secure network transmissions on some Unix versions when tcp wrappers are turned on... a) look in /etc/hosts.allow file for allowed firewall access results logged to syslog b) look in /etc/hosts.deny file for denied firewall access c) if no rules apply, then access is granted optionally sends banners to clients can transfer access to “ jail ” or “ faux ” Free BSD OS X varies with Linux

echo (UDP Port 7) ping command sends datagram to test connectivity systat (TCP Port 11) netstat command returns user names, login times, and so forth ftp (TCP Ports 20 & 21) file transfer protocol ftp transmits in plaintext - sftp encrypts anonymous ftp is a vulnerability ssh (TCP Port 2) secure shell for remote login uses symmetric encryption (ssh.config) requires that client have public key telnet (TCP Port 23) original remote login shell - uses plaintext

smtp (TCP Port 25) Simple Mail Transfer Protocol - Internet standard for transfer dns (TCP & UDP Port 53) Domain Name System (stay tuned) dhcp (UDP Ports 67 & 68) Dynamic Host Configuration Protocol IP address leasing utility finger (TCP Port 79) retrieves user info (name, location, login, telephone, and so forth http (TCP Ports 80 & 443) HypterText Transfer Protocol (WWW protocol) POP, POPS, IMAP, IMAPS (TCP Ports 109, 110, 143, 993 & 995) Post Office Protocol -- Internet Message Access Protocol snmp (UDP Ports 161 & 162) Simple Network Management Protocol remote system management tool rlogin & rsh (TCP Ports 513 & 514) more insecure login shells empty /etc/hosts.equiv