1. Berkeley R Utilities & the new S Utilities The Unix (or Berkeley) r utilities provide an alternative to IP facilities telnet and ftp. Three programs: rlogin hostname remote login rsh hostname command remote command rcp [ host :] file [ host :] file remote copy, from to scp user1@host:file user2@host:filesecure copy, from touser1@host:file ssh hostnameremote command rdist remote distrubtuion For R family: passwords not required if.rhosts files configured –friendly hosts defined for all normal users in /etc/hosts.equiv –users may add to this list in $HOME/.rhosts For S family: you need to exchange keys (RedHat 9+ default) –Users may add friendly hosts in $HOME/.ssh/authorized_keys –Keys must be give to you from remote host $HOME/.ssh/id_rsa.pub –Keys generated with ssh-keygen –t rsa –Is installed by default in most Unixes nowdays (R Family is not)

2. Exercise - Who has Remote Access Here are three files from mash4077 Can root on seoul copy files to/from mash4077? Can hawkeye on seoul run commands on mash4077? Can hawkeye on rosies run commands on mash4077? Can root on mash4077 copy files to/from rosies? Can bfpierce on division copy files to mash4077? Can root on seoul login to mash4077? # more /etc/hosts.equiv seoul # more /.rhosts rosies # /home/hawkeye/.rhosts rosies swamp division bfpierce # more /etc/hosts.equiv seoul # more /.rhosts rosies # /home/hawkeye/.rhosts rosies swamp division bfpierce

3. Remote shells The rsh (remsh) command –run a command on a named host –standard I/O can be redirected as normal –/etc/profile and.profile not executed –requires /etc/hosts.equiv or $HOME/.rhosts file to be configured From a02 or a03 you issue the commands below: $ whoami trapper $ rsh a01 ls -l..run ls –l as trapper on a01 output.. $ rsh a01 ls -l > list.a01 file list.a01 created on local system $ rsh a01...same as rlogin... $ rsh –l hawkeye a01...same as rlogin –l hawkeye... $ whoami trapper $ rsh a01 ls -l..run ls –l as trapper on a01 output.. $ rsh a01 ls -l > list.a01 file list.a01 created on local system $ rsh a01...same as rlogin... $ rsh –l hawkeye a01...same as rlogin –l hawkeye...

4. Remote distribution -rdist The rdist command –replicating/maintain identical copies of files over multiple hosts –relies on rlogin and rsh –can use ssh as transport for secure mode –rdist is client software and rdistd is server software –the server rdistd is started via rsh or ssh on the server –R-family rsh requires: /etc/hosts.equiv or $HOME/.rhosts file to be configured –S-family ssh requires: $HOME/.ssh/rsa_key.pub to be copied from remote server/client –Uses a special file Distfile for updating and maintaining files –Can syslog to /var/log/messages file RDIST HOME: http://www.magnicomp.com/rdist/ http://www.magnicomp.com/rdist/ The rdist command is SuSE standard

5. Remote distribution –preparation Pepare a master-server and a client files to replicate 1.Logins must be done without password on clients, or rdist fails. 2.With R-Family: setup server and clients like in this chapter. 3.With S-Family: Generate keys and distribute server keys to all clients, look below. 4.S-Family: Enable ssh root-logins on all clients. 5.Create a Distfile with files and directories to update on your clients with. Enable root logins (trusted enviroment only) on all clients: 1.sshd config file: /etc/ssh/sshd_config: PermitRootLogin yes AuthorizedKeysFile.ssh/authorized_keys

6. Remote distribution –preparation test Generate server private and public keys: 1.As root generate server keys on server: # ssh-keygen –t rsa 2.Copy keys to identity files: # cd.ssh ; cp id_rsa identity ; cp id_rsa.pub identity.pub Distribute public keys to clients: 1.Create client private and public keys: # ssh ssh-keygen –t rsa 2.Distribute server public key to all your clients (they need /root/.ssh catalog): # scp identity.pub :.ssh/authorized_keys As root on the server, test root password-less login rights to all of the nodes/clients by: # ssh node01 date sat dec 12 14:52:55 CET 2004

7. Remote distribution -Distfile Used to specify how replication should take place The Distfile format: `=' [ label: ] `->' [ label: ] `::' The label is optional. HOSTS is in our example all hosts and logins that FILES can be replicated to/from ${FILES} -> ${HOSTS} sends files to list of hosts. /usr/src/bin -> arpa sends catalog with contents to host arpa Commands list is instrcution howto install/operate with lists/files

8. Remote distribution –execute rdist Create some testfiles to distribute among clients. # vi /etc/my-rdist-testfile This is the rdist test file! Create a Distfile This file willl replicate the ETCFILES onto all the NODES. Replicate the files using rdist together with SSH You may want to run this command every night on your master-server by using the crontab command. NODES = ( a01 a02 a03 a04 ) ETCFILES = ( /etc/my-rdist-testfile ) ${ETCFILES} -> ${NODES} install; NODES = ( a01 a02 a03 a04 ) ETCFILES = ( /etc/my-rdist-testfile ) ${ETCFILES} -> ${NODES} install; # /usr/local/bin/rdist -P /usr/local/bin/ssh -p /usr/local/bin/rdistd -f /etc/Distfile

9. Internetwork demon Configuration Internet facilities controlled by the internet daemon –/usr/sbin/xinetd –started up from /etc/inittab xinetd controlled by configuration file /etc/xinetd.conf –Tells where application to start is located –Set mandatory user/group to run application –Former name was inetd.conf and inetd demon –Declares service name Services configuration files /etc/xinetd.d/ : service telnet { disable = no flags = REUSE socket_type = stream wait = no user = root server = /usr/sbin/in.telnetd log_on_failure += USERID } service telnet { disable = no flags = REUSE socket_type = stream wait = no user = root server = /usr/sbin/in.telnetd log_on_failure += USERID }

10. Summary Unix systems use TCP/IP for networking Every host on the network must have a unique IP address The file /etc/hosts maps names into IP addresses for network utilities Systems using DNS don't keep local host files Unix supports standard TCP/IP programs such as ping, telnet and ftp Unix provides its own equivalents (rlogin, rcp/scp, rsh and rdist) which use.rhosts files Unix uses several TCP/IP configuration files in /etc (xinetd.conf, services, etc.)