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  • Blacklisting Kernel Modules
    06/12/2016 12:14PM

    Following is a walkthrough on how to blacklist a kernel module.  The specific example is blacklisting the nouveau driver so that I can install the OEM Nvidia driver.

    1. First, blacklist the nouveau driver: Add a line to the textfile /etc/modprobe.d/nouveau-blacklist.conf that contains they keyword 'blacklist' and the name of the driver

    blacklist nouveau

    2. Rebuild the initramfs image file.  First, backup existing initramfs


    # mv initramfs-3.10.0-327.18.2.el7.x86_64.img initramfs-3.10.0-327.18.2.el7.x86_64.img_2016-06-09.bak

    Build new initramfs
    # dracut -v /boot/initramfs-$(uname -r).img $(uname -r)

    3. Reboot the system and confirm that the driver in question is not loaded.
    # lsmod | fgrep nouveau

  • How to Return Hive Query Results Similary to MySQL \G in One Vertical Column
    06/09/2016 4:03PM

    When trying to look at data in a database with really wide rows even just selecting 1 row to see the data is nearly impossible to understand when the single row wraps 7 or 8 times.

    MySQL offers the '\G' option to display the output in a single column.

    The corresponding method in Hive is to execute the following set command:

    !SET outputformat vertical;

  • How to Configure a User Account in Active Directory So that the Password Never Expires
    06/09/2016 3:54PM

    Using ADSI Edit, navigate to the user in question.  Right-click on the user and select Properties.

    Then, scroll down to the 'userAccountControl' property and click the Edit button.

    Enter 66048 into the field and then click 'OK' and then 'Apply'.

    After closing the edit window, scroll to the right to confirm that the value indicates the following: '0x10200 = (NORMAL_ACCOUNT|DONT_EXPIRE_PASSWORD)'

  • Using netcat to Mock a RESTful Webservice that Returns JSON
    05/10/2016 10:26AM

    Let's say that you are working on a part of a project that needs to consume some JSON data from a forthcoming HTTP service.  That sub-system is being developed by one of your colleagues and is not yet ready for you to stand-up to develop against.

    You can use netcat to mock the webservice and return some static JSON data for which you can develop and test against with a simple one-liner.

    First, put together your JSON in a file, 'my.json' and then run the following command in a terminal:

    while true; do echo -e "HTTP/1.1 200 OK\r\n\r\n$(cat my.json)" | nc -l 9998; done

    An hitting http://localhost:9998 will return your test JSON data.

  • How to Use Credentials That Contain Special Characters with curl
    05/02/2016 12:00PM
    In order to execute curl commands to endpoints with passwords that contain special characters, the cleanest way that I have found to do so is to Base64 encode the authentication string for curl and then pass an Authorization request header along with the request.

    In this example the credentials are uid 'rchapin' and passwd 'abc123!@#'.  Normally we would pass this to curl as follows:

    $ curl -u rchapin:abc123!@# -X GET https://some-endpoint:443

    However, this will not work and the password will need to be sent in some other fashion other than ASCII.

    Following are the steps to pass the credentials as Base64:

    1. Using your favorite Base64 encoder, generate and ASCII string of the entire 'username:password' strin
    g that you would normally pass with the -u option for curl

    rchapin:abc123!@# converted = cmNoYXBpbjphYmMxMjMhQCM=

    2. Now modify the curl command as follows:

    $ curl -H "Authorization: Basic cmNoYXBpbjphYmMxMjMhQCM=" -X GET https://some-endpoint:443
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