• MCE hardware error cpu 0

    1.0 Error


    While running Ubuntu 18.04.1 on a laptop, the following errors were observed.

    mce: hardware error cpu 0 machine check 0 bank 6 ae0000000040110a
    mce: hardware error tsc 0 addr ffb07540 misc 238a0000086
    mce: hardware error processor 0:40651 time 1540082330 socket 0 Apic 0 microcode 24
    ipmi dmi invalid offset 0

    The system would stop in ...

  • Failed to fetch webpage, temporary failure resolving domain

    1.0 Error

    While configuring a Linux server, the error Failed to fetch webpage, temporary failure resolving domain was observed.

    $ sudo apt-get update
    Err:1 ... bionic InRelease
      Temporary failure resolving ...
    Err:2 ... bionic-updates InRelease
      Temporary failure resolving ...
    Reading package lists... Done
    W: Failed to fetch ...  Temporary failure resolving ...

    Also, the

  • Composer Manager: Composer’s install command must be run

    1.0 Error

    After updating the Drupal 7 version in a website, the following error was observed in the configuration of the Composer Manager module.

    Composer Manager: Composer's install command must be run to generate the autoloader and install the required packages.

    The above message was followed by the status of packages managed by the Composer. ...

  • Drupal: Notice: Trying to get property of non-object in block_block_view()

    1.0 Error

    After updating the website to a new version of Drupal 7, the following error was printed on the web pages.

    Notice: Trying to get property of non-object in block_block_view() (line 247 of modules/block/block.module).

    2.0 Resolution

    The error was resolved by the following steps.

    2.1 Turn off block caching

    From the Administration menu, Select Configuration –> Development ...

  • Dovecot: Fatal: Error in configuration file /etc/dovecot/dovecot.conf: protocols: Unknown protocol: sieve

    1.0 Error:

    While configuring the Dovecot Mail Delivery Agent, the Dovecot server would not start and the following error messages were printed.

    $ sudo systemctl start dovecot
    Job for dovecot.service failed because the control process exited with error code. See "systemctl status dovecot.service" and "journalctl -xe" for details.
    $ systemctl status dovecot.service
    ● dovecot.service - Dovecot IMAP/POP3 ...
  • How to execute PHP code in HTML under nginx server

    1.0 Error

    PHP code was not getting executed in the index.html file when the concerned website was opened in a browser. nginx server was being used to serve the web pages.

    2.0 Solution

    2.1 Install php7.0-fpm

    $ sudo apt-get install php7.0-fpm


  • SSL Certificate expired, site not opening

    1.0 ERROR

    A website stopped opening in browser, giving the error that the SSL certificate was either invalid or had expired.


    Checking the website with wget,

    $ wget https://www.example.com
    --2018-01-14 16:58:36--  https://www.example.com/
    Resolving www.example.com (www.example.com)..., 2001:db8:1221:2341:f03c:f27b:12fa:2123
    Connecting to www.example.com (www.example.com)||:443... connected.ERROR: cannot verify www.example.com's certificate, issued by ‘CN=Typical Encryption Authority X3,O=Typical Encryption,C=XX’:
      Issued certificate ...
  • How to preserve exif metadata in images in Linux

    1.0 Exif metadata not preserved by image editing program

    Problem: After an image is developed and edited by image editing software and saved in a format like JPEG, it does not have the Exif metadata.

    2.0 Solution

    Surprisingly, quite a few image editing programs do not preserve the Exif metadata of images and attempts ...

  • How to add IPTC metadata in photographs using exiv2 in Linux

    1.0 Adding the IPTC metadata

    After a photograph has been taken and processed, it might be necessary to add IPTC metadata before it can be published. If your image editing software does not support adding of IPTC metadata to the image, you can accomplish this is by using the exiv2 command ...

  • How to get the value of Pi in bc calculations

    1.0 π

    While using bc for calculations, the value of π is sometimes required. Sure, you might remember it as 3.1416, but it is better to use a higher precision value. And it's quite simple to do that.

    First, we need to start bc with the option

  • Error while executing the dig command

    1.0 Error

    While executing the dig command, the sendmsg() failed: Operation not permitted error was printed.

    $ dig example.com
    ../../../../lib/isc/unix/net.c:581: sendmsg() failed: Operation not permitted
    ../../../../lib/isc/unix/net.c:581: sendmsg() failed: Operation not permitted

    2.0 Solution

    The error was resolved after adding the following iptables rules.

    iptables -I OUTPUT 1 -p udp -s ...
  • Analyzing the NGINX web server log file

    1.0 Introduction

    Given an nginx web server log file, we might like to know who are the visitors to our website. One can go line by line through the log file, but that is tedious. It would be nice if we can get one line per client visiting the website, giving the IP ...

  • Android adb install failure INSTALL_PARSE_FAILED_NO_CERTIFICATES

    1.0 Error

    A signed APK of an Android app was built using the Android Studio. When we tried to download the signed APK to a device using the adb command, the command failed with the error, INSTALL_PARSE_FAILED_NO_CERTIFICATES.

    $ adb install app-release.apk 
    app-release.apk: ...
  • nginx drupal sitemap 404 not found

    1.0 Error

    While trying to open sitemap.xml of a site served by nginx and built using Drupal CMS, the 404 Not Found error was received. The nginx log file, error.log gave the error as, 80 open() sitemap.xml failed (2: No such file or directory).

    2.0 ...

  • optipng: Error: Can’t back up the existing output file

    1.0 Error

    While running optipng on a png file, the following error was obtained,

    Error: Can't back up the existing output file

    2.0 Solution

    The file was not having the write permission. Once, the write mode bit for the file was set, optipng worked fine.

    $ ls -ls ...