The default xcache admin username and password are

username = useradmin
password = userpassword

Added xcache admin directory to /usr/local/nginx/html/myxcacheadmin/ 

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Changing username/passwords for xcache admin page
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You need to setup admin password as per instructions at http://xcache.lighttpd.net/wiki/InstallAdministration for your /usr/local/lib/php.ini. 

So edit php.ini the default user/pass.

note: userpassword's md5 hash converted value = d440aed189a13ff970dac7e7e8f987b2

[xcache.admin]
xcache.admin.enable_auth = On
xcache.admin.user = "useradmin"
xcache.admin.pass = "d440aed189a13ff970dac7e7e8f987b2"

Change username of your choosing and to create an md5 hashed password as per instructions at http://xcache.lighttpd.net/wiki/InstallAdministration and replace the xcache.admin.pass md5 hash with your updated password