gh-20: add check for readable linux kernel

lib/cangallo.rb

@@ -22,6 +22,7 @@
 require 'cangallo/libguestfs'
 require 'cangallo/keybase'
 require 'cangallo/version'
+require 'cangallo/check'
 
 class Cangallo
   def initialize

lib/cangallo/check.rb

@@ -0,0 +1,63 @@
+
+# vim:tabstop=2:sw=2:et:
+
+# Copyright 2016, Javier Fontán Muiños <[email protected]>
+#
+# Licensed under the Apache License, Version 2.0 (the "License"); you may
+# not use this file except in compliance with the License. You may obtain
+# a copy of the License at
+#
+# http://www.apache.org/licenses/LICENSE-2.0
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+require 'rubygems'
+
+class Cangallo
+  class Check
+    def initialize
+    end
+
+    def check
+      valid = true
+
+      valid = valid_kernel = check_kernel
+      help_kernel if !valid_kernel
+
+
+      if !valid
+        text = "There is at least one one problem in your system."
+
+        STDERR.puts
+        STDERR.puts text
+      end
+
+      valid
+    end
+
+    def check_kernel
+      Dir['/boot/vmlinuz*'].each do |file|
+        if File.readable?(file)
+          return true
+        end
+      end
+
+      false
+    end
+
+    def help_kernel
+      text = <<-EOT
+libguestfs needs a kernel to boot it's qemu appliance. There is no kernel
+in your /boot directory readable by your kernel. Change the permissions of
+at least one kernel in that directory to be readable by the current user.
+      EOT
+
+      STDERR.puts text
+    end
+  end
+end
+