Suppose we have a computer with Ubuntu Linux installed. If we want to access this computer remotely through SSH protocol, we must enable SSH server first. To enable SSH server on Ubuntu Linux, we must install openssh-server
package first :
tedy@tedy-laptop:~$ sudo apt-get install openssh-server Reading package lists... Done Building dependency tree Reading state information... Done The following packages were automatically installed and are no longer required: libwxgtk2.8-0 kdebase-data kicker libkonq4 libwxbase2.8-0 Use 'apt-get autoremove' to remove them. Suggested packages: molly-guard rssh The following NEW packages will be installed: openssh-server 0 upgraded, 1 newly installed, 0 to remove and 0 not upgraded. Need to get 0B/252kB of archives. After this operation, 668kB of additional disk space will be used. WARNING: The following packages cannot be authenticated! openssh-server Install these packages without verification [y/N]? y Preconfiguring packages ... Selecting previously deselected package openssh-server. (Reading database ... 199826 files and directories currently installed.) Unpacking openssh-server (from .../openssh-server_4.7p1-8ubuntu1_i386.deb) ... Setting up openssh-server (1:4.7p1-8ubuntu1) ... Creating SSH2 RSA key; this may take some time ... Creating SSH2 DSA key; this may take some time ... * Restarting OpenBSD Secure Shell server sshd [ OK ]
After install the package, the sshd
daemon will run automatically. We can check the status of the SSH daemon by using check the process and port, SSH server by default listen on port 22 :
tedy@tedy-laptop:~$ ps -ef | grep sshd root 8228 1 0 08:37 ? 00:00:00 /usr/sbin/sshd tedy 8248 7815 0 08:38 pts/2 00:00:00 grep sshd tedy@tedy-laptop:~$ tedy@tedy-laptop:~$ netstat -an | grep LISTEN | grep :22 tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN tcp6 0 0 :::22 :::* LISTEN tedy@tedy-laptop:~$
To restart SSH daemon we use the following command (need root priviledge to do that) :
root@tedy-laptop:/home/tedy# /etc/init.d/ssh restart * Restarting OpenBSD Secure Shell server sshd [ OK ] root@tedy-laptop:/home/tedy# /etc/init.d/ssh restart
Below is the output example when trying to do SSH on that machine :
login as: tedy tedy@10.191.75.201's password: Linux tedy-laptop 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i6 86 GNU/Linux Ubuntu 10.04 LTS Welcome to Ubuntu! * Documentation: https://help.ubuntu.com/ Last login: Tue Jan 4 22:54:26 2011 from mytestbed.local tedy@tedy-laptop:~$
As you can see on above example, Ubuntu show last login display everytime we access it using SSH. To prevent Ubuntu display last login info when somebody login into the system using SSH, we can edit /etc/ssh/sshd_config
and set PrintLastLog parameter to NO.
tedy@tedy-laptop:~$ cat /etc/ssh/sshd_config .... .... X11Forwarding yes X11DisplayOffset 10 PrintMotd no PrintLastLog no TCPKeepAlive yes UseLogin yes .... .... #MaxStartups 10:30:60 Banner /etc/issue.net
Besides SSH, Ubuntu can be accessed through telnet protocol as long as it has telnet server running. To install telnet server on Ubuntu (package name is telnetd
) we do it like this :
root@vpn-test:/home/tedy# apt-get install telnetd Reading package lists... Done Building dependency tree Reading state information... Done The following extra packages will be installed: openbsd-inetd The following NEW packages will be installed: openbsd-inetd telnetd 0 upgraded, 2 newly installed, 0 to remove and 0 not upgraded. Need to get 0B/76.9kB of archives. After this operation, 283kB of additional disk space will be used. Do you want to continue [Y/n]? Y WARNING: The following packages cannot be authenticated! openbsd-inetd telnetd Install these packages without verification [y/N]? y Selecting previously deselected package openbsd-inetd. (Reading database ... 99838 files and directories currently installed.) Unpacking openbsd-inetd (from .../openbsd-inetd_0.20050402-6_i386.deb) ... Selecting previously deselected package telnetd. Unpacking telnetd (from .../telnetd_0.17-35ubuntu1_i386.deb) ... Setting up openbsd-inetd (0.20050402-6) ... * Stopping internet superserver inetd [ OK ] * Not starting internet superserver: no services enabled. Setting up telnetd (0.17-35ubuntu1) ... Adding user telnetd to group utmp root@vpn-test:/home/tedy#
To check the availability of telnet server we can check the by using this command (remember that telnetd
process listen on port 23 by default):
root@vpn-test:/home/tedy# netstat -an | grep LISTEN | grep ":23 " tcp 0 0 0.0.0.0:23 0.0.0.0:* LISTEN root@vpn-test:/home/tedy#
Below is the output example when trying to do telnet on that machine :
Ubuntu 10.04 LTS vpn-test login: tedy Password: Last login: Wed Jan 5 11:24:44 WIT 2011 from dhcp-id-jakata-10-181-190-235.id.oracle.com on pts/0 Linux vpn-test 2.6.32-21-generic #32-Ubuntu SMP Fri Apr 16 08:10:02 UTC 2010 i686 GNU/Linux Ubuntu 10.04 LTS Welcome to Ubuntu! * Documentation: https://help.ubuntu.com/ tedy@vpn-test:~$
Thank you.
Excelente. me fue de utilidad ;)
wonderfulll , teruskan mas…. saya tunggu artikel selanjutnya
Very nice tutorial, thank you very much!
Hi I tried to run :sudo apt-get install openssh-server but I got the error : unable locate package
, my ubuntu laptop has internet connection, pls help me to solve this
@skyranger : it would be the problem with your repository. Please check your sources list file & run sudo apt-get update first.
first : apt-cache search openssh-server
then : apt-get install update
next : apt-get install openssh-server
if it still error, you can download openssh-server packege form internet and install it.
root@ubuntu:~# apt-get install telnetd
Reading package lists… Done
Building dependency tree
Reading state information… Done
E: Couldn’t find package telnetd
@sandip :
– check your ubuntu repository
– do apt-get update first before searching the packet