<sect1 id="troubleshooting-network-x"> <sect1info> <authorgroup> <author>&J.Hall;</author> </authorgroup> </sect1info> <title>Networking and X</title> <para> Misconfigured networking can often be the cause of &tde; applications launching slowly, or in the worst case not launching at all. Your &X-Server; has a very powerful client/server interface and is very network aware. </para> <para> X uses the hostname to create both a unique key for authorization, and to figure out where (via $<envar>DISPLAY</envar>) to send the actual windows it's drawing on screen. If your computer doesn't know it's own name, it will spend inordinate amounts of time trying to look itself up, a fate you can avoid by simply teaching your computer what it's own name is. </para> <para> Check your <filename>/etc/hosts</filename> file and ensure there is an entry for localhost that looks something like this at the top of the file (after any comments). </para> <screen> 127.0.0.1 localhost </screen> <para> You also should add your computers fully qualified domain name, short name, and it's usual ip address if it has a static ip. If your ip address is assigned dynamically using <acronym>DHCP</acronym> you can simply use the address for the loopback device. </para> <screen> 127.0.0.1 hal.btl hal (for dhcp) 192.168.0.1 hal.btl hal (static) </screen> <para> Make sure that your firewall is not so restrictive that it stops packets to the loopback device. For example in iptables if the default rule on the <parameter>INPUT</parameter> chain for this device is set to anything other than <parameter>>ACCEPT</parameter> this will cause performance problems in X. To check this, you can type in: </para> <screen> <prompt>%</prompt><userinput><command>iptables-save</command> <literal>|</literal> <command>grep</command> <option>lo</option></userinput> <computeroutput><option>-A</option> <parameter>INPUT</parameter> <option>-i</option> <parameter>lo</parameter> <option>-j</option> <parameter>ACCEPT</parameter> </computeroutput> </screen> <para> The rule <computeroutput><option>-A</option> <parameter>INPUT</parameter> <option>-i</option> <parameter>lo</parameter> <option>-j</option> <parameter>ACCEPT</parameter></computeroutput> should always work, unless there are other misconfigured rules (Such as a <parameter>DROP</parameter> on the <parameter>OUTPUT</parameter> chain) </para> </sect1>