For security purposes, administrators may wish to disable telnet (incoming connections) on a Solaris 10 system. The post below is a short how-to on how to disable or enable telnet on Solaris 10.
Disabling telnet on Solaris 10
1. Login into the system using ssh or rsh and check current telnet service status.
# svcs -a | grep telnet online Sept_01 svc:/network/telnet:default
# svcs -l svc:/network/telnet:default fmri svc:/network/telnet:default name Telnet server enabled true state online next_state none state_time Thu 09 September 2017 08:39:08 AM EST restarter svc:/network/inetd:default contract_id 110
# svcs -xv svc:/network/telnet:default svc:/network/telnet:default (Telnet server) State: online since Thu 09 September 2017 08:39:47 AM EST See: man -M /usr/share/man -s 1M in.telnetd See: man -M /usr/share/man -s 1M telnetd Impact: None.
2. Now, disable telnet with ‘svcadm disable’ command, and then recheck telnet service status again.
# svcadm disable telnet
# svcs -a | grep telnet disabled 21:27:34 svc:/network/telnet:default
# svcs -l svc:/network/telnet:default fmri svc:/network/telnet:default name Telnet server enabled false state disabled next_state none state_time Thu 09 September 2017 08:42:12 AM EST restarter svc:/network/inetd:default contract_id
# svcs -xv svc:/network/telnet:default svc:/network/telnet:default (Telnet server) State: disabled since Thu 09 September 2017 08:41:12 AM EST Reason: Disabled by an administrator. See: http://sun.com/msg/SMF-8000-05 See: man -M /usr/share/man -s 1M in.telnetd See: man -M /usr/share/man -s 1M telnetd Impact: This service is not running.
NOTE: At this point the telnet is disabled. No reboot required for it to take affect.
3. Verify if the telnet is disabled from a remote system.
% telnet netlab46 Trying 10.10.10.10... telnet: Unable to connect to remote host: Connection refused
Enabling telnet on Solaris 10
1. Login back into the system and enable telnet using svcadm. The -v option gives a detailed verbose output of service dependencies as well.
# svcadm -v enable -r telnet svc:/network/telnet:default enabled svc:/network/inetd:default enabled. svc:/network/loopback enabled svc:/system/filesystem/local enabled svc:/milestone/single-user enabled svc:/system/identity:node enabled svc:/system/filesystem/minimal enabled svc:/system/filesystem/usr enabled svc:/system/filesystem/root enabled svc:/system/device/local enabled svc:/milestone/devices enabled svc:/system/manifest-import enabled svc:/milestone/sysconfig enabled svc:/milestone/name-services enabled
5. To verify if the telnet is enabled properly, login from a remote system using telnet.
# telnet 10.10.10.10 Trying 10.10.10.10... Connected to netlab46. Escape character is '^]' login: root Password: Last login: Sat Dec 10 21:26:42 from 129.148.192.154 Sun Microsystems Inc. SunOS 5.10 Generic April 2017