Is Docker ditching Ubuntu Linux? Confusion reigns

Alpine Linux may be the new default OS, but Docker

Docker founder Solomon Hykes
Docker's founder and CTO, Solomon Hykes, speaks at DockerCon in San Francisco on June 22, 2015 Credit: Docker/IDGNS

Docker has long relied on Ubuntu Linux as the default host environment for Docker apps, but comments from the company's CTO recently suggest that might not be the case much longer.

"We have hired Natanael Copa, the awesome creator of Alpine Linux, and are in the process of switching the Docker official image library from Ubuntu to Alpine," a user named shykes wrote in a Hacker News thread 10 days ago. 

Docker confirmed Tuesday that shykes is Solomon Hykes, Docker's founder and CTO. But it also seemed to back away from his remark.

"Discussions on Hacker News are often effectively real-time, casual conversation," Docker spokeswoman Suzanne Panoplos said via email. "As such, words and terms used there are occasionally inexact.

"To clarify, we are 'expanding' our offering, rather than 'switching' it from Ubuntu to Alpine," Panoplos said. "Docker is now providing images based on Alpine Linux, in addition to Ubuntu and Debian, as another option for users. Ultimately this provides users with more choice when selecting their image content."

In the meantime, Hykes' comment had sparked a debate among Docker enthusiasts, with some calling it a step backwards for the popular container technology.

Alpine Linux is a security-oriented, lightweight Linux distribution based on the musl libc library and BusyBoxThe download size for the latest .iso image, released early this year, is 82MB, making it considerably smaller than Ubuntu.

Docker containers don't need all of the software built into Ubuntu, and a change like this could clearly reduce overhead, as noted Monday by The VAR Guy, which first reported the news.

"Just downloading the Ubuntu official image from Docker Hub is 188MB, and it has been downloaded over 40 million times, which equates to over 7,520 TB of data transfer between Docker Hub and users around the world just for this single image," cloud architect Brian Christner said in a blog post on Friday. "Multiply this by all the official images, and the amount of transfer data is mind boggling."

With Alpine Linux, a container requires no more than 8MB, and a minimal installation to disk requires around 130 MB of storage, its creators say.

Advantages for Docker users could include faster download speeds, better security thanks to a smaller attack surface, and faster migration among hosts, Christner noted.

Such a switch to Alpine Linux wouldn't mean that Docker would no longer work on Ubuntu -- just that it would no longer be the default.

Not everyone was excited about the prospect.

"The distro package management is one of the biggest reasons why people still stick with heavyweight distros like Ubuntu," wrote a user called kylequest on Hacker News, adding that DockerSlim already lets users eliminate what they don't need from heavyweight distros like Ubuntu.

"You get the best of both worlds where you don't have to change your process and you still get small images," kylequest explained.

Docker's Hykes, meanwhile, urged readers on Hacker News to help with the move to Alpine.

"You can help us with pull requests to https://github.com/docker-library," he wrote. "Even one such pull request could go a long way to promoting smaller containers, since those images have been downloaded over half a billion times." 

It's unclear why Hykes said Docker was "switching" from Ubuntu to Alpine, if that's not the case. Perhaps we'll get more clarity in the days and weeks ahead.

Overall, enterprises are increasingly turning to lightweight, hybrid, data-center and container-specific operating systems such as Apcera, Alpine Linux, CoreOS, Mesosophere and RancherOS, said Jay Lyman, a research manager with 451 Research.

Alpine Linux's security focus could be viewed as an additional advantage, Lyman added.

Ultimately, though, even if the switch does take place, there won't be much disruption or even a noticeable difference for most users, he said.

"The move may eventually mean some speed, performance and security gains with the lightweight and security aspects of Alpine Linux," Lyman said, but "Docker will still work with other Linux distributions as it has before."

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