虚拟映像优化

应优化虚拟机以在KVM管理程序上更高效地运行。 考虑到企业拥有大量的虚拟机管理程序和虚拟机，没有优化，性能可能会受到影响。 应在VM上进行的更改因系统内核设置而异。 在本节中，我将提供您可以采取的各种步骤来优化图像。

在进行CentOS或RedHat安装时，请选择“最小安装”，而不是其他任何内容。 此策略可减小图像的大小。 较小的图像克隆速度更快，即使您使用Kickstart，它们的安装速度也会更快。 此外，您只需要最少的软件包就可以减少安全风险。

# Configure tuned for virtual guest
# tuned-adm profile virtual-guest
# chkconfig tuned on

tuned是一个系统调优守护程序，它根据配置文件设置各种系统/内核参数。

禁用不需要的服务 保持启用它们会降低启动过程并存在安全风险。 以下是一些可能被关闭的服务：

# for svc in ip6tables cups abrtd abrt-ccpp atd kdump mdmonitor NetworkManager; do chkconfig $svc off; done
root# for svc in ip6tables cups abrtd abrt-ccpp atd kdump mdmonitor NetworkManager; do service $svc stop; done
# Disable IPv6 if you are not using it.
# echo "NETWORKING_IPV6=no
IPV6INIT=no" >> /etc/sysconfig/network
# echo "
# Disable IPv6.
net.ipv6.conf.all.disable_ipv6 = 1
net.ipv6.conf.default.disable_ipv6 = 1
" >> /etc/sysctl.conf
# smartd monitors hard drives; no need for that on a VM
root# service smartd stop
root# chkconfig --del smartd
# Allow virsh shutdown to turn of the VM.
# If we do a minimal CentOS install, acpid is not installed by default.
# yum install acpid
# chkconfig acpid on
# service acpid start

要使用virsh console命令访问VM的控制台，必须通过串行控制台重定向VM控制台输出。 以下步骤说明如何执行此操作：

# Getting serial console to work on KVM with RHEL 6 and also with GRUB
# Comment out splashimage and hiddenmenu
# Remove 'rhgb' and 'quiet' from the kernel line
# Add the 'serial' and the 'terminal' line
# Add the last two 'console' parameters on the kernel line
# Now try to access the serial console using 'virsh console <hostname>'
# cat /etc/grub.conf
# grub.conf generated by anaconda
#
# Note you do not have to rerun grub after making changes to this fil.e
# NOTICE: You have a /boot partition. This means that
# all kernel and initrd paths are relative to /boot/, e.g.,
# root (hd0,0)
# kernel /vmlinuz-version ro root=/dev/mapper/vg_ns-lv_root
# initrd /initrd-[generic-]version.img
# boot=/dev/vda
default=0
timeout=10
serial --unit=0 --speed=115200
terminal --timeout=5 serial console
#splashimage=(hd0,0)/grub/splash.xpm.gz
#hiddenmenu
title CentOS (2.6.32-431.el6.x86_64)
 root (hd0,0)
 kernel /vmlinuz-2.6.32-431.el6.x86_64 ro root=/dev/mapper/vg_ns-lv_root rd_NO_LUKS LANG=en_US.UTF-8 rd_NO_MD SYSFONT=latarcyrheb-sun16 rd_LVM_LV=vg_ns/lv_root crashkernel=auto KEYBOARDTYPE=pc KEYTABLE=us rd_LVM_LV=vg_ns/lv_swap rd_NO_DM console=tty0 console=ttyS0,115200
 initrd /initramfs-2.6.32-431.el6.x86_64.img