Hi all,

Several folks have asked for a definition of what's supposed to be in an Atomic Host -- which is sort of loosely defined currently, but a more explicit definition is in order.

Including a discussion draft based on working documents for RHEL Atomic here. Apologies for sending it to such a wide audience (CentOS, Fedora, and Atomic-devel) but I know we have participants who are only on one of the lists.

The text is below in Markdown and I've also created a Gist [1] should anyone wish to send patches that way.

Note there's a full list of packages at the end, from the RHEL work. This is not to say "Atomic must include these packages" but "here's what we're currently working with."

[1] https://gist.github.com/jzb/0f336c6f23a0ba145b0a#file-atomic-host-definition

Thoughts, comments, flames?

Best,

jzb

# # #

# Atomic Host Definition [Discussion Draft]

This document is meant to serve as a baseline definition for Project Atomic hosts, to be implemented from CentOS, Fedora, and Red Hat Enterprise Linux (RHEL).

The purpose of the document is not to restrict the packages or services offered with an Atomic host, but to ensure a baseline of functionality and working standard that each product team can implement **before** adding additional functionality.

The initial working draft is being taken from work going into RHEL Atomic, but it is expected that the CentOS Atomic SIG and Fedora Cloud Workgroup will provide input and direction to Project Atomic going forward. This is simply the first cut at a shared understanding that gives each team a basis for cooperation.

## Atomic Host Definition

The next section provides some guidance on how an Atomic host differs from other products that are provided by the distributions, and the expectations that projects should convey to users.

### What is an Atomic Host?

The Atomic Host is a minimal set of packages and services essential to running and orchestrating containers:

* Minimal Footprint: An Atomic Host should have a minimal footprint with only essential technologies needed to run containers. Services that can or should be run in a container should *not* be part of the Atomic Host.

* Container Host Optimized: The Atomic Host **must** be able to build, deploy, and run containers "out of the box." The Atomic host is a single-purpose OS, customized to run containers and that's all. Additional services and applications should be deployed in containers, not added to the host.

* Support for Docker Container Format: Fairly self-explanatory, the Atomic host should include all applications and services required to run Docker containers.

* Atomic Update and Rollback Capability: Using rpm-ostree/OStree, Atomic hosts will support atomic updates and rollbacks to the previous release state.

* Provided as a tree defined by the project team (not RPMs), with updated trees for errata and minor releases.

- DIY Atomic Trees: It's up to the project whether they wish to provide tools and guidance (documentation) around building their own Atomic trees.

* Rolling Stream of Updates: The expectation is that Atomic hosts will not have an "overlapping stream" of supported releases. Instead, users will be expected to move to an updated release rather than stay on a specific release version.

- Example: Fedora 20 Atomic Host will receive monthly updates while Fedora 21 is in development. When Fedora 21 Atomic Host is released, the next update for users on Fedora 20 Atomic Host will carry them to Fedora 21, and so forth. **At this time we won't plan to carry overlapping versions of the operating system for Atomic Host users.**

* Multi-host orchestration capabilities for Atomic Host infrastructure.

* Multi-host infrastructure for application containers.

* x86_64 Only: Current plans are for the Atomic Host to be x86_64 only.

* Target platforms: KVM (qcow2), Baremetal, AWS AMI, and GCE.

### Compatibility With Parent Distribution

The Atomic Host is composed of packages from the parent distribution and is expected to be compatible with CentOS, Fedora, or RHEL (respectively) and its behavior should not differ from the parent distribution where similar functionality exists.

* ABI/KABI Compatibility: Atomic Host is generally compatible with underlying ABI and KABI for common packages.

* Exceptions to ABI compatibility: Docker and Kubernetes *may* break ABI compatibility.

* Unique Packages: May be composed from sources outside the standard distribution (e.g., EPEL, Copr trees).

* Release Versioning: Numbering will follow parent distribution.

* Asynchronous Updates: The Atomic host functionality may move ahead of parent distribution where necessary.

* For example, an update in Anaconda may be needed that isn't yet available in CentOS 7. The Atomic version of Anaconda may move ahead of CentOS 7 if necessary and sync up at a later date.

* Long-term divergence is *not* planned. Any instances where packages diverge from the parent distribution needs to be tracked, and a plan in place to ensure the packages sync up in time.

## Goals for Atomic Hosts

The goal for the Atomic Host is *not* to be a full, general purpose, operating system. It's a single-purpose host designed to run Docker containers and provide orchestration tools to manage containers at scale.

* Independent release cadence from parent distribution to respond to rapidly changing ecosystem.

* Deliver images for bare metal and important cloud/virtualization platforms (AWS, GCE, KVM, OpenStack).

* Minimal footprint.

## Package Definition:

### Newer than / different from RHEL/CentOS 7

* tuned * glib2 * glib-networking * libsoup * docker * hawkey * libsolv * authconfig * python-blivet * anaconda * pykickstart * lorax * systemd

### New Packages

* nss-altfiles * libgsystem * ostree * rpm-ostree-client

### Compose Tooling

* rpm-ostree * rpm-ostree-toolbox

### Appendix A: Full Package List (RHEL 7 Atomic)

ModemManager-glib-1.1.0-6.git20130913.el7.x86_64 NetworkManager-0.9.9.1-26.git20140326.4dba720.el7_0.x86_64 NetworkManager-glib-0.9.9.1-26.git20140326.4dba720.el7_0.x86_64 PyYAML-3.10-11.el7.x86_64 acl-2.2.51-12.el7.x86_64 audit-2.3.3-4.el7.x86_64 audit-libs-2.3.3-4.el7.x86_64 audit-libs-python-2.3.3-4.el7.x86_64 avahi-0.6.31-13.el7.x86_64 avahi-autoipd-0.6.31-13.el7.x86_64 avahi-libs-0.6.31-13.el7.x86_64 basesystem-10.0-7.el7.noarch bash-4.2.45-5.el7.x86_64 bash-completion-2.1-6.el7.noarch bind-libs-9.9.4-14.el7.x86_64 bind-libs-lite-9.9.4-14.el7.x86_64 bind-license-9.9.4-14.el7.noarch bind-utils-9.9.4-14.el7.x86_64 binutils-2.23.52.0.1-16.el7.x86_64 bridge-utils-1.5-9.el7.x86_64 btrfs-progs-3.12-4.el7.x86_64 bzip2-libs-1.0.6-12.el7.x86_64 c-ares-1.10.0-3.el7.x86_64 ca-certificates-2013.1.95-71.el7.noarch cadvisor-0.4.0-0.0.git5a6d06c0.el7.centos.x86_64 checkpolicy-2.1.12-6.el7.x86_64 chkconfig-1.3.61-4.el7.x86_64 cloud-init-0.7.5-1.el7_0.x86_64 coreutils-8.22-11.el7.x86_64 cpio-2.11-22.el7.x86_64 cracklib-2.9.0-11.el7.x86_64 cracklib-dicts-2.9.0-11.el7.x86_64 cronie-1.4.11-11.el7.x86_64 cronie-anacron-1.4.11-11.el7.x86_64 crontabs-1.11-6.20121102git.el7.noarch cryptsetup-libs-1.6.3-2.el7.x86_64 cups-libs-1.6.3-14.el7.x86_64 curl-7.29.0-19.el7.x86_64 cyrus-sasl-gssapi-2.1.26-17.el7.x86_64 cyrus-sasl-lib-2.1.26-17.el7.x86_64 dbus-1.6.12-8.el7.x86_64 dbus-glib-0.100-7.el7.x86_64 dbus-libs-1.6.12-8.el7.x86_64 dbus-python-1.1.1-9.el7.x86_64 device-mapper-1.02.84-14.el7.x86_64 device-mapper-event-1.02.84-14.el7.x86_64 device-mapper-event-libs-1.02.84-14.el7.x86_64 device-mapper-libs-1.02.84-14.el7.x86_64 device-mapper-persistent-data-0.3.2-1.el7.x86_64 dhclient-4.2.5-27.el7_0.1.x86_64 dhcp-common-4.2.5-27.el7_0.1.x86_64 dhcp-libs-4.2.5-27.el7_0.1.x86_64 diffutils-3.3-4.el7.x86_64 dmidecode-2.12-5.el7.x86_64 dnsmasq-2.66-12.el7.x86_64 docker-1.2.0-17.el7.x86_64 dracut-033-161.el7.x86_64 e2fsprogs-1.42.9-4.el7.x86_64 e2fsprogs-libs-1.42.9-4.el7.x86_64 elfutils-libelf-0.158-3.el7.x86_64 etcd-0.4.6-3.el7.centos.x86_64 ethtool-3.8-3.el7.x86_64 expat-2.1.0-8.el7.x86_64 file-libs-5.11-21.el7.x86_64 filesystem-3.2-18.el7.x86_64 findutils-4.5.11-3.el7.x86_64 fipscheck-1.4.1-5.el7.x86_64 fipscheck-lib-1.4.1-5.el7.x86_64 freetype-2.4.11-9.el7.x86_64 gawk-4.0.2-4.el7.x86_64 gdbm-1.10-8.el7.x86_64 geard-0-0.7.3.atomic.git78f7ef1.el7.x86_64 git-1.8.3.1-4.el7.x86_64 glib-networking-2.40.1-1.atomic.el7.x86_64 glib2-2.40.0-1.atomic.el7.x86_64 glibc-2.17-55.el7_0.1.x86_64 glibc-common-2.17-55.el7_0.1.x86_64 gmp-5.1.1-5.el7.x86_64 gnupg2-2.0.22-3.el7.x86_64 gnutls-3.1.18-9.el7_0.x86_64 gobject-introspection-1.36.0-4.el7.x86_64 gpgme-1.3.2-5.el7.x86_64 grep-2.16-1.el7.x86_64 groff-base-1.22.2-8.el7.x86_64 grubby-8.28-8.el7.x86_64 gsettings-desktop-schemas-3.8.2-3.el7.x86_64 gzip-1.5-7.el7.x86_64 hardlink-1.0-19.el7.x86_64 hawkey-0.4.12-3.atomic.1.el7.x86_64 hostname-3.13-3.el7.x86_64 info-5.1-4.el7.x86_64 initscripts-9.49.17-1.el7_0.1.x86_64 iproute-3.10.0-13.el7.x86_64 iptables-1.4.21-13.el7.x86_64 iputils-20121221-6.el7.x86_64 irqbalance-1.0.6-5.el7.x86_64 jansson-2.4-6.el7.x86_64 jbigkit-libs-2.0-11.el7.x86_64 json-c-0.11-4.el7_0.x86_64 json-glib-0.16.0-3.el7.x86_64 kernel-3.10.0-123.8.1.el7.x86_64 keyutils-libs-1.5.8-3.el7.x86_64 kmod-14-9.el7.x86_64 kmod-libs-14-9.el7.x86_64 kpartx-0.4.9-66.el7.x86_64 krb5-libs-1.11.3-49.el7.x86_64 kubernetes-0.2-0.9.gitf7a5ec3.el7.centos.x86_64 less-458-8.el7.x86_64 libacl-2.2.51-12.el7.x86_64 libarchive-3.1.2-7.el7.x86_64 libassuan-2.1.0-3.el7.x86_64 libattr-2.4.46-12.el7.x86_64 libbasicobjects-0.1.0-22.el7.x86_64 libblkid-2.23.2-16.el7.x86_64 libcap-2.22-8.el7.x86_64 libcap-ng-0.7.3-5.el7.x86_64 libcgroup-0.41-6.el7.x86_64 libcollection-0.6.2-22.el7.x86_64 libcom_err-1.42.9-4.el7.x86_64 libcurl-7.29.0-19.el7.x86_64 libdaemon-0.14-7.el7.x86_64 libdb-5.3.21-17.el7_0.1.x86_64 libdb-utils-5.3.21-17.el7_0.1.x86_64 libdhash-0.4.3-22.el7.x86_64 libedit-3.0-12.20121213cvs.el7.x86_64 libestr-0.1.9-2.el7.x86_64 libevent-2.0.21-4.el7.x86_64 libffi-3.0.13-11.el7.x86_64 libgcc-4.8.2-16.2.el7_0.x86_64 libgcrypt-1.5.3-4.el7.x86_64 libgnome-keyring-3.8.0-3.el7.x86_64 libgpg-error-1.12-3.el7.x86_64 libgsystem-2014.2-2.atomic.el7.x86_64 libgudev1-208-12.atomic.4.el7.centos.x86_64 libidn-1.28-3.el7.x86_64 libini_config-1.0.0.1-22.el7.x86_64 libipa_hbac-1.11.2-68.el7_0.5.x86_64 libjpeg-turbo-1.2.90-5.el7.x86_64 libldb-1.1.16-4.el7.x86_64 libmnl-1.0.3-7.el7.x86_64 libmodman-2.0.1-8.el7.x86_64 libmount-2.23.2-16.el7.x86_64 libndp-1.2-4.el7.x86_64 libnetfilter_conntrack-1.0.4-2.el7.x86_64 libnfnetlink-1.0.1-4.el7.x86_64 libnl-1.1.4-3.el7.x86_64 libnl3-3.2.21-6.el7.x86_64 libnl3-cli-3.2.21-6.el7.x86_64 libpath_utils-0.2.1-22.el7.x86_64 libpcap-1.5.3-3.el7.x86_64 libpipeline-1.2.3-3.el7.x86_64 libproxy-0.4.11-6.el7.x86_64 libpwquality-1.2.3-4.el7.x86_64 libref_array-0.1.3-22.el7.x86_64 libselinux-2.2.2-6.el7.x86_64 libselinux-python-2.2.2-6.el7.x86_64 libselinux-utils-2.2.2-6.el7.x86_64 libsemanage-2.1.10-16.el7.x86_64 libsemanage-python-2.1.10-16.el7.x86_64 libsepol-2.1.9-3.el7.x86_64 libsolv-0.6.4-2.el7.x86_64 libsoup-2.45.90-2.atomic.git20140601.2.el7.x86_64 libss-1.42.9-4.el7.x86_64 libssh2-1.4.3-8.el7.x86_64 libsss_idmap-1.11.2-68.el7_0.5.x86_64 libstdc++-4.8.2-16.2.el7_0.x86_64 libtalloc-2.0.8-4.el7.x86_64 libtasn1-3.3-5.el7_0.x86_64 libtdb-1.2.12-3.el7.x86_64 libteam-1.9-15.el7.x86_64 libtevent-0.9.18-6.el7.x86_64 libtiff-4.0.3-14.el7.x86_64 libuser-0.60-5.el7.x86_64 libutempter-1.1.6-4.el7.x86_64 libuuid-2.23.2-16.el7.x86_64 libverto-0.2.5-4.el7.x86_64 libwbclient-4.1.1-37.el7_0.x86_64 libwebp-0.3.0-3.el7.x86_64 libxml2-2.9.1-5.el7.x86_64 libxml2-python-2.9.1-5.el7.x86_64 libyaml-0.1.4-10.el7.x86_64 linux-firmware-20140804-0.1.git6bce2b0.el7_0.noarch lm_sensors-libs-3.3.4-10.el7.x86_64 logrotate-3.8.6-4.el7.x86_64 lua-5.1.4-14.el7.x86_64 lvm2-2.02.105-14.el7.x86_64 lvm2-libs-2.02.105-14.el7.x86_64 lzo-2.06-6.el7_0.2.x86_64 m2crypto-0.21.1-15.el7.x86_64 man-db-2.6.3-9.el7.x86_64 man-pages-3.53-5.el7.noarch mozjs17-17.0.0-10.el7.x86_64 mtools-4.0.18-5.el7.x86_64 nano-2.3.1-10.el7.x86_64 ncurses-5.9-13.20130511.el7.x86_64 ncurses-base-5.9-13.20130511.el7.noarch ncurses-libs-5.9-13.20130511.el7.x86_64 net-tools-2.0-0.17.20131004git.el7.x86_64 nettle-2.7.1-2.el7.x86_64 nmap-ncat-6.40-4.el7.x86_64 nspr-4.10.6-1.el7_0.x86_64 nss-3.16.2-2.el7_0.x86_64 nss-altfiles-0-1.atomic.git20131217gite2a80593.el7.x86_64 nss-softokn-3.16.2-1.el7_0.x86_64 nss-softokn-freebl-3.16.2-1.el7_0.x86_64 nss-sysinit-3.16.2-2.el7_0.x86_64 nss-tools-3.16.2-2.el7_0.x86_64 nss-util-3.16.2-1.el7_0.x86_64 numactl-libs-2.0.9-2.el7.x86_64 openldap-2.4.39-3.el7.x86_64 openssh-6.4p1-8.el7.x86_64 openssh-clients-6.4p1-8.el7.x86_64 openssh-server-6.4p1-8.el7.x86_64 openssl-libs-1.0.1e-34.el7_0.4.x86_64 ostree-2014.6-2.atomic.el7.x86_64 p11-kit-0.18.7-4.el7.x86_64 p11-kit-trust-0.18.7-4.el7.x86_64 pam-1.1.8-9.el7.x86_64 passwd-0.79-4.el7.x86_64 pcre-8.32-12.el7.x86_64 perl-5.16.3-283.el7.x86_64 perl-Carp-1.26-244.el7.noarch perl-Encode-2.51-7.el7.x86_64 perl-Error-0.17020-2.el7.noarch perl-Exporter-5.68-3.el7.noarch perl-File-Path-2.09-2.el7.noarch perl-File-Temp-0.23.01-3.el7.noarch perl-Filter-1.49-3.el7.x86_64 perl-Getopt-Long-2.40-2.el7.noarch perl-Git-1.8.3.1-4.el7.noarch perl-HTTP-Tiny-0.033-3.el7.noarch perl-PathTools-3.40-5.el7.x86_64 perl-Pod-Escapes-1.04-283.el7.noarch perl-Pod-Perldoc-3.20-4.el7.noarch perl-Pod-Simple-3.28-4.el7.noarch perl-Pod-Usage-1.63-3.el7.noarch perl-Scalar-List-Utils-1.27-248.el7.x86_64 perl-Socket-2.010-3.el7.x86_64 perl-Storable-2.45-3.el7.x86_64 perl-TermReadKey-2.30-20.el7.x86_64 perl-Text-ParseWords-3.29-4.el7.noarch perl-Time-Local-1.2300-2.el7.noarch perl-constant-1.27-2.el7.noarch perl-libs-5.16.3-283.el7.x86_64 perl-macros-5.16.3-283.el7.x86_64 perl-parent-0.225-244.el7.noarch perl-podlators-2.5.1-3.el7.noarch perl-threads-1.87-4.el7.x86_64 perl-threads-shared-1.43-6.el7.x86_64 pinentry-0.8.1-14.el7.x86_64 pkgconfig-0.27.1-4.el7.x86_64 policycoreutils-2.2.5-11.el7.x86_64 policycoreutils-python-2.2.5-11.el7.x86_64 polkit-0.112-5.el7.x86_64 polkit-pkla-compat-0.1-4.el7.x86_64 popt-1.13-16.el7.x86_64 ppp-2.4.5-33.el7.x86_64 procps-ng-3.3.9-6.el7.x86_64 pth-2.0.7-22.el7.x86_64 pygobject2-2.28.6-11.el7.x86_64 pygobject3-base-3.8.2-4.el7.x86_64 pygpgme-0.3-9.el7.x86_64 pyliblzma-0.5.3-11.el7.x86_64 pytalloc-2.0.8-4.el7.x86_64 python-2.7.5-16.el7.x86_64 python-IPy-0.75-6.el7.noarch python-backports-1.0-6.el7.noarch python-backports-ssl_match_hostname-3.4.0.2-4.el7.noarch python-boto-2.25.0-2.el7.noarch python-chardet-2.0.1-7.el7.noarch python-cheetah-2.4.4-5.el7.x86_64 python-configobj-4.7.2-7.el7.noarch python-dateutil-1.5-7.el7.noarch python-decorator-3.4.0-3.el7.noarch python-dmidecode-3.10.13-11.el7.x86_64 python-ethtool-0.8-5.el7.x86_64 python-iniparse-0.4-9.el7.noarch python-jsonpatch-1.2-2.el7.noarch python-jsonpointer-1.0-2.el7.noarch 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