Improve postinstall

packaging/debian/postinst

@@ -41,11 +41,10 @@ case "$1" in
     ${CLI} config:set WEB_CONCURRENCY=${web_concurrency}
 
     # set SECRET_TOKEN env variable
-    secret_token=$(${CLI} config:get SECRET_TOKEN || ( < /dev/urandom tr -dc a-z0-9 | head -c128; echo ))
+    secret_token=$(${CLI} config:get SECRET_TOKEN || ${CLI} run rake -s secret | tail -1)
     ${CLI} config:set SECRET_TOKEN="$secret_token"
 
     # migrate
-    ADMIN_EMAIL=$(${CLI} config:get ADMIN_EMAIL || echo "admin@example.com")
     ${CLI} run rake ${rake_commands} || true
 
     sys_api_key=$(${CLI} config:get SYS_API_KEY)