Thinking In Software

Saturday, September 30, 2017

Replace the CRLF or ^M by LF

Saturday, September 16, 2017

Auditing file changes in Linux

Audit the file by adding a watch, tail the audit log, remove the watch and list current watches in case you need to remove others.

sudo auditctl -w /path/to/file -p wa
sudo tail -f /var/log/audit/audit.log
sudo auditctl -W /path/to/file -p wa
sudo auditctl -l

Thursday, August 03, 2017

shortcut to get into a kubernetes pod shell

$ grep -B0 -F3 kbash ~/.bashrc
function kbash() {
  kubectl exec -ti $1 bash
}

Usage:

kbash some-pod-name-here

Friday, July 28, 2017

Fastest way to inspect web server HTTP traffic

ngrep -W byline port 80

Thursday, June 08, 2017

The network folder specified is currently mapped using a different name and password

Getting "The network folder specified is currently mapped using a different name and password. To connect using a different user name and password, first disconnect any existing mappings to this network share"?

This happened to me after a failed attempt to map a path I had no access to with my regular user. Selecting to map it with different credentials kept on complaining with this error message. The solution was to:

Run 'net use' and if the path is present run 'net /delete \\path\to\resource' and/or 'net /delete $DRIVE_LETTER:'
Run 'runas /profile /user:$DOMAIN\$USER cmd' for any privileged $USER you have used before. Hopefully is not administrator ;-)
From the new command prompt pertaining to the privilege user follow the first step
Try to map the drive again as you would usually do (in my case using the "Connect using different credentials")

tail: inotify cannot be used, reverting to polling: Too many open files

Run 'ps -ef' and look for some processes that might be unusually big in number.

Friday, May 19, 2017

The meaning of VueJS "render: h => h(App)"

What is the meaning of the arrow function defining the 'render' VueJS method?:

import Vue from 'vue'
import App from './App.vue'

new Vue({
  el: '#app',
  render: h => h(App)
})

From https://vuejs.org/v2/guide/render-function.html

Aliasing createElement to h is a common convention you’ll see in the Vue ecosystem and is actually required for JSX. If h is not available in the scope, your app will throw an error.

Therefore here is the equivalent of the previous code:

import Vue from 'vue'
import App from './App.vue'

new Vue({
  el: '#app',
  render: function(createElement) {
    return createElement(App);
  }
})

The arrow function meaning is: let 'render' be a function that accepts the createElement() function as argument and that returns createElement(App) where App is a VueJS single-file-component. Here is a working example showing the equivalent of this arrow function. Below is the complete code as well:

<!DOCTYPE html>
<html>
<body>
  <div id="app">
  </div>
  <script src="https://unpkg.com/vue@2.3.3"></script>
  <script type="text/javascript">
    new Vue({
      el: '#app',
      // render is a function defined here as accepting the function h as parameter and returning the h result when evaluated with a single file component or in this case a template (in here two params: the tag and the value)
      render: h => h('h1', 'Hello')
      // Same but probably easier to understand for most humans who prefer long but straightforward text rather than short but cryptic:
      /*render: function(createElement) {
        return createElement('h1', 'Hello');
      }*/
    })
  </script>
</body>
</html>

BTW there is a cryptic-er way to use a single file component (the ES6 spread operator):

import Vue from 'vue'
import App from './App.vue'

new Vue({
  el: '#app',
  ...App
})