Docker: Visualizing image hierarchy and container dependency using dockviz

The Docker console commands for listing and viewing containers and images (ps, images, history, inspect) provides a wealth of information, but when you are managing hundreds of containers, a graph view of the container inventory and their dependencies can be critical for operations.

Dockviz can help you visualize your containers and images by creating an PNG image representing the container links and image lineage.

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OpenWrt: Upgrading OpenWrt to the latest snapshot build

Although stables releases of OpenWrt come out every 6 to 12 months, the automatically built snapshots offer a way to embrace the latest features, patches, and  security fixes without waiting that long.

A sysupgrade procedure works by saving the configuration files from known locations, deleting the entire filesystem, installing the new version of OpenWrt,  and then restoring the configuration files.

This is usually painless, but there can be issues if configuration changes have been made in non-standard file locations and are not saved.  Additionally, custom packages do not survive the sysupgrade and have to be reinstalled (to ensure compatibility with the kernel) and their new configurations must be manually merged.

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Unbutu: Removing unused kernel images and headers

As part of normal long-term operations, the number of kernel images on your system will accumulate and take up disk space.  This issue with space will be even more pronounced if /boot is mounted to its own smaller partition.

With Ubuntu 16.04, ‘apt autoremove –purge’ and configuration of the unattended upgrades can ensure that old kernel images are cleaned, but if you are using Ubuntu 14.04 or need to manually purge, then the instructions below can lead you through the process.

Before removing this unnecessary baggage, the first step is to check what kernel version is currently being used and the installation state.

> uname -r
4.4.0-57-generic

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OpenWrt: Installing a TFTP Server on Ubuntu for OpenWrt Firmware Updates

openwrt_logoThe Trivial File Transfer Protocol (TFTP) is an extremely simple protocol most often used for network booting strategies, such as PXE and flashing OpenWrt images unto consumer routers.

I go over full instructions for flashing OpenWrt using Ubuntu and flashing a sysupgrade in another post, this article will focus specifically on setting up a tftp server daemon on Ubuntu that can be used to serve the binary image file.

Installation

First, install the tftp server and client packages:

# apt-get install tftpd-hpa tftp-hpa -y

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