title: getting error while updating Composer
body: <p>I have a project in Laravel-5.1 and I have changed my platform from win10 to Ubuntu.</p>
  <p>Showing error:</p>
  <blockquote>
  <p>Loading composer repositories with package information</p>
  <p>Updating dependencies (including require-dev)</p>
  <p>Your requirements could not be resolved to an installable set of packages.</p>
  </blockquote>
  <pre><code>  Problem 1
  - laravel/framework v5.2.9 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.8 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.7 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.6 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.5 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.4 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.31 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.30 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.3 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.29 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.28 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.27 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.26 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.25 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.24 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.23 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.22 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.21 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.20 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.2 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.19 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.18 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.17 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.16 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.15 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.14 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.13 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.12 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.11 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.10 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.1 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.0 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - laravel/framework v5.2.30 requires ext-mbstring * -&gt; the requested PHP extension mbstring is missing from your system.
  - Installation request for laravel/framework 5.2.* -&gt; satisfiable by laravel/framework[v5.2.0, v5.2.1, v5.2.10, v5.2.11, v5.2.12, v5.2.13, v5.2.14, v5.2.15, v5.2.16, v5.2.17, v5.2.18, v5.2.19, v5.2.2, v5.2.20, v5.2.21, v5.2.22, v5.2.23, v5.2.24, v5.2.25, v5.2.26, v5.2.27, v5.2.28, v5.2.29, v5.2.3, v5.2.30, v5.2.31, v5.2.4, v5.2.5, v5.2.6, v5.2.7, v5.2.8, v5.2.9].
  
  To enable extensions, verify that they are enabled in those .ini files:
  - /etc/php/7.0/cli/php.ini
  - /etc/php/7.0/cli/conf.d/10-mysqlnd.ini
  - /etc/php/7.0/cli/conf.d/10-opcache.ini
  - /etc/php/7.0/cli/conf.d/10-pdo.ini
  - /etc/php/7.0/cli/conf.d/20-calendar.ini
  - /etc/php/7.0/cli/conf.d/20-ctype.ini
  - /etc/php/7.0/cli/conf.d/20-exif.ini
  - /etc/php/7.0/cli/conf.d/20-fileinfo.ini
  - /etc/php/7.0/cli/conf.d/20-ftp.ini
  - /etc/php/7.0/cli/conf.d/20-gettext.ini
  - /etc/php/7.0/cli/conf.d/20-iconv.ini
  - /etc/php/7.0/cli/conf.d/20-json.ini
  - /etc/php/7.0/cli/conf.d/20-mysqli.ini
  - /etc/php/7.0/cli/conf.d/20-pdo_mysql.ini
  - /etc/php/7.0/cli/conf.d/20-phar.ini
  - /etc/php/7.0/cli/conf.d/20-posix.ini
  - /etc/php/7.0/cli/conf.d/20-readline.ini
  - /etc/php/7.0/cli/conf.d/20-shmop.ini
  - /etc/php/7.0/cli/conf.d/20-sockets.ini
  - /etc/php/7.0/cli/conf.d/20-sysvmsg.ini
  - /etc/php/7.0/cli/conf.d/20-sysvsem.ini
  - /etc/php/7.0/cli/conf.d/20-sysvshm.ini
  - /etc/php/7.0/cli/conf.d/20-tokenizer.ini
  You can also run `php --ini` inside terminal to see which files are used by PHP in CLI mode.
  </code></pre>
  <p>Composer/json.</p>
  <pre><code>{
  &quot;name&quot;: &quot;laravel/laravel&quot;,
  &quot;description&quot;: &quot;The Laravel Framework.&quot;,
  &quot;keywords&quot;: [&quot;framework&quot;, &quot;laravel&quot;],
  &quot;license&quot;: &quot;MIT&quot;,
  &quot;type&quot;: &quot;project&quot;,
  &quot;require&quot;: {
    &quot;php&quot;: &quot;&gt;=5.5.9&quot;,
    &quot;laravel/framework&quot;: &quot;5.2.*&quot;,
    &quot;infyomlabs/laravel-generator&quot;: &quot;dev-master&quot;,
    &quot;laravelcollective/html&quot;: &quot;5.2.*&quot;,
    &quot;infyomlabs/core-templates&quot;: &quot;dev-master&quot;,
    &quot;infyomlabs/swagger-generator&quot;: &quot;dev-master&quot;,
    &quot;jlapp/swaggervel&quot;: &quot;dev-master&quot;,
    &quot;doctrine/dbal&quot;: &quot;~2.3&quot;,
    &quot;infyomlabs/generator-builder&quot;: &quot;dev-master&quot;,
    &quot;yajra/laravel-datatables-oracle&quot;: &quot;~6.0&quot;,
    &quot;barryvdh/laravel-ide-helper&quot;: &quot;^2.1&quot;,
    &quot;infyomlabs/adminlte-templates&quot;: &quot;dev-master&quot;
  },
  &quot;require-dev&quot;: {
      &quot;fzaninotto/faker&quot;: &quot;~1.4&quot;,
      &quot;mockery/mockery&quot;: &quot;0.9.*&quot;,
      &quot;phpunit/phpunit&quot;: &quot;~4.0&quot;,
      &quot;symfony/css-selector&quot;: &quot;2.8.*|3.0.*&quot;,
      &quot;symfony/dom-crawler&quot;: &quot;2.8.*|3.0.*&quot;
  },
  &quot;autoload&quot;: {
      &quot;classmap&quot;: [
          &quot;database&quot;
      ],
      &quot;psr-4&quot;: {
          &quot;App\\&quot;: &quot;app/&quot;
      }
  },
  &quot;autoload-dev&quot;: {
      &quot;classmap&quot;: [
          &quot;tests/TestCase.php&quot;
      ]
  },
  &quot;scripts&quot;: {
      &quot;post-root-package-install&quot;: [
          &quot;php -r \&quot;copy('.env.example', '.env');\&quot;&quot;
      ],
      &quot;post-create-project-cmd&quot;: [
          &quot;php artisan key:generate&quot;
      ],
      &quot;post-install-cmd&quot;: [
          &quot;Illuminate\\Foundation\\ComposerScripts::postInstall&quot;,
          &quot;php artisan optimize&quot;
      ],
      &quot;post-update-cmd&quot;: [
          &quot;Illuminate\\Foundation\\ComposerScripts::postUpdate&quot;,
          &quot;php artisan optimize&quot;
      ]
  },
  &quot;config&quot;: {
      &quot;preferred-install&quot;: &quot;dist&quot;
  }
  </code></pre>
  <p>}</p>