Ubuntu Server 12.04新特性打造最佳服务器

　　文件系统

　　CEPH 客户端库, librbd 和 librados 添加到 KVM 的支持中
　　CIFS 使用文件系统缓存以提升性能
　　软 RAID 支持坏块管理

　　ARM 支持

　　提供 OpenMPI 1.5 for ARM  (889644)
　　openmpi 1.5 改进对 ARM 的支持，不过目前还是 beta 版本。

　　其他

　　Query2, 一个新的元数据服务，用来描述 Ubuntu 云图片以及其可用性，提供一个 JSON 格式的文件用来描述 cloud-images.ubuntu.com 上的图片存储和官方 Ubuntu 图片的状态

　　新的 Zentyal 包

These packages are a rename of the existing ebox packages along with a new upstream release fixing known issues in the current ebox packages in Ubuntu 11.10.

Resara, 一个开源的 Linux 域控制器和文件服务器，基于 Samba4.
acpid introduced to both Server and Cloud images by default.

Chef 0.8.16 (948437) and corresponding Ohai packages (948438) removed from precise at the request of OpsCode.

应 Eucalyptus 的要求移除 Eucalyptus 2.0.1 (953405)

　　通用架构

Up until Ubuntu 11.10, administrator access using the sudo tool was granted via the “admin” Unix group. In Ubuntu 12.04, administrator access will be granted via the “sudo” group. This makes Ubuntu more consistent with the upstream implementation and Debian. For compatibility purposes, the “admin” group will continue to provide sudo/administrator access in 12.04.

　　默认禁用休眠功能(suspend to disk) ，因为发现这功能不可靠，而且两种不同的挂起模式让人混淆，详情请看 bug 812394.
pm-utils now has two new scripts to power down USB and various PCI devices in battery mode. A number of desktop packages were fixed to wake up less often. Both of these reduce power consumption and thus improve battery lifetime.

resolvconf is now used to manage /etc/resolv.conf on all Ubuntu systems. You can learn more here
Backports are now more easily accessible -- to enable users to more easily receive new versions of software, the Ubuntu Backports repository is now enabled by default. Packages from backports will not be installed by default — they must explicitly be selected in package management software. However, once installed, packages from backports will automatically be upgraded to newer versions.
DVD Images -- the DVD images have been cleaned up significantly reducing their size to around 1.5GB to ease consumption. The remaining software remains available via download.

　　Linux v3.2.14 内核

Ubuntu 12.04 LTS ships with an updated kernel moving from the mainline v3.0 series to the mainline v3.2 series. At release we are shipping with the Ubuntu 3.2.0-23.36 kernel which is based on the v3.2.14 upstream stable Linux kernel. The mainline v3.0 to v3.2 stable series update brings a number of new features. Some highlights include:

ext4 gains support for larger base block sizes
btrfs has more work addressing data integrity issues
device mapper gains thin provisioning and recursive snapshots
more work to improve performance under high writeback load
networking improvements for congested networks
ext3 moves to using filesystem barriers
memory allocator improvements
VFS scalability improvements
a new iSCSI implementation
software wait gains bad block management

Key changes in the Ubuntu kernel since the 3.0.0-12.20 Ubuntu kernel as shipped in the 11.10 Ubuntu release include:

Rebase to upstream stable Linux kernel v3.2.14.

The amd64 -generic and -server kernel flavors have been merged into a single -generic kernel flavor for Ubuntu 12.04. Given the few differences that existed between the two flavors, it only made sense to merge the two and reduce the overall maintenance burden over the life of this LTS release.
Support for a new armhf kernel flavor has been introduced.

The non-smp PowerPC kernel flavor has been removed. All hardware currently supported by the non-smp PowerPC kernel flavor should also be supported by the smp PowerPC kernel flavor.

RC6 is enabled by default for Sandy Bridge systems. RC6 is a technology which allows the GPU to go into a very low power consumption state when the GPU is idle (down to 0W). It results in considerable power savings when this stage is activated. When comparing under idle loads with machine state where RC6 is disabled, improved power usage of around 40-60% has been witnessed.

An improved set of jack detection patches has been backported from the upstream v3.3 Linux kernel.

An updated AppArmor patch set has been included to better align with what is landing upstream.

Applied and enabled the seccomp filters feature which uses the packet filtering machinery (BPF) to restrict access to system calls.

A set of kexec fixes for arm from v3.3-rc1 has also been backported.

We’ve also conducted an extensive review of Ubuntu kernel configs and made numerous config changes as a result.

　　Upstart 1.5

　　Upstart 更新到 1.5. Upstart Technical Overview 提供更详细的细节

　　GNU Toolchain

　　Ubuntu 12.04 包含默认的工具链：GCC 4.6.3 (and changes from Linaro GCC 4.6-2012.02), binutils 2.22, eglibc 2.15, and Linaro gdb 7.4-2012.04.

　　与 11.10 版本比较主要是一些增量的改动和 bug 修复

　　更新的前端以更好的支持标准 (Ada 2012, Objective-C 2.0, improved experimental support for the upcoming C++0x ISO C++ standard, Fortran 2003 and 2008 improvements, new Go frontend)
改进优化、更好的过程优化和链接时间优化。

　　更多的信息请看 (GCC-4.6, GCC-4.5, binutils, gas, ld, gdb).

　　Python Toolchain

　　Ubuntu 12.04 包含 Python 2.7.3 和 Python 3.2.3，不再提供 Python 2.6
该版本为 Python 3 提供扩展支持, 包括 Python 3 移植版本的：python-dbus, python-feedparser, germinate, lazr.ui, wadllib, python-defer, python-keyring, and python-qt4 now included, among others.

　　Java Toolchain

　　默认的 Java 运行环境采用 OpenJDK 6b24 (IcedTea 1.11.1). 同时也提供 OpenJDK 7u3 (IcedTea 2.1)