最後更新: 2019-02-15

介紹

 

KVM 的 console 是透過 serail port 去實現的.

在 Linux 裡, 一般 console 是一個 character device 來

"virtio console device" 中的 device 則是 /dev/hvc[0-7] 其一個 (<target type='virtio' port='0'/>)

 

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VM Guest 的 XML

 

設定 VM guest 有 console

<console type='pty'></console>

由於 console 一定是 serial port 來, 所以保存後會有

<serial type='pty'>
      <target port='0'/>
</serial>
<console type='pty'>
      <target type='serial' port='0'/>
</console>

serial and console elements have partially overlapping scopes.

difference between the two is that serial is used for emulated, usually native, serial consoles,

whereas console is used for paravirtualized ones (virsh # console myvm)

可以用以下一句給一個真實(Host 上)的 serial port 給 VM guest

<devices>
  <!-- Serial port -->
  <serial type='pty'>
    <source path='/dev/pts/3'/>        # host interface
    <target port='0'/>
  </serial>
</devices>

進入 console

virsh # console seafile

Connected to domain seafile
Escape character is ^]

離開 console (返回 Shell)

Ctrl+]

Or

Ctrl+5

 

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Serial Port Login Shell

 

除了 VM 要設定好 device 外, Guest OS 亦要有所設定才同到 virsh console

找出 serial port:

dmesg | grep ttyS

serial8250: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A
00:05: ttyS0 at I/O 0x3f8 (irq = 4) is a 16550A

                OR

yum install setserial

setserial -g /dev/ttyS*

/dev/ttyS0, UART: 16550A, Port: 0x03f8, IRQ: 4
/dev/ttyS1, UART: unknown, Port: 0x02f8, IRQ: 3
/dev/ttyS2, UART: unknown, Port: 0x03e8, IRQ: 4
/dev/ttyS3, UART: unknown, Port: 0x02e8, IRQ: 3

-g: arguments to setserial are interpreted as a list of devices

Ubuntu-12.04:

用 upstart 實現:

/etc/init/ttyS0.conf

start on stopped rc RUNLEVEL=[2345]
stop on runlevel [!2345]

respawn
exec /sbin/getty -L 38400 ttyS0 vt102

Debian6:

用 init 實現:

修改 /etc/inittab

default 是有 "#" 在前面的 !

T0:23:respawn:/sbin/getty -L ttyS0 38400 linux

之後執行

init q

Centos6:

修改 /etc/securetty

........................
# 加入
ttyS0

/etc/init/serial.conf

# Automatically start a configured serial console (port is in /etc/securetty)

# 它 default 只會去找 /dev/console, 所以, 我們要建立以下檔案

/etc/init/ttyS0.conf

# ttyS0 - agetty
#
# This service maintains a agetty on ttyS0.

stop on runlevel [S016]
start on runlevel [23]

respawn
exec agetty -h -L -w /dev/ttyS0 115200 vt102

Centos7:

stty -F /dev/ttyS0 speed 115200

systemctl start serial-getty@ttyS0

systemctl enable serial-getty@ttyS0

Created symlink from /etc/systemd/system/getty.target.wants/[email protected] to
 /usr/lib/systemd/system/[email protected].

Remark

To make use of a serial console, just use console=ttyS0 on the kernel command line(/proc/cmdline),

and systemd will automatically start a getty on it for you.

By default systemd will instantiate one [email protected] on the main kernel console.

In systemd, two template units are responsible for bringing up a login prompt on text consoles:

[email protected] is responsible for virtual terminal (VGA screen)(/dev/tty1 ...)

* echo $TERM    # Result: linux

[email protected] is responsible for all other terminals (/dev/ttyS0 ...)

* echo $TERM    # Result: vt102

virtio-serial (Centos7)

Channel is exposed in the guest under /dev/vport*,

and if the optional element name is specified, /dev/virtio-ports/$name

With qemu, if name is "org.qemu.guest_agent.0",

then libvirt can interact with a guest agent installed in the guest,
(for actions such as guest shutdown or file system quiescing)

設定 virtio console

<console type='pty'>
    <target type='virtio'/>
</console>

save 後會變成

<console type='pty'>
    <target type='virtio' port='0'/>
</console>

<controller type='virtio-serial' index='0'>
    <address type='pci' domain='0x0000' bus='0x00' slot='0x07' function='0x0'/>
</controller>

Guest 的設定

Guest 啟動後會有 /dev/hvc0, 並且會由 systemd-getty-generator 啟動 getty

(/usr/lib/systemd/system-generators/systemd-getty-generator)

ps a | grep hvc0

3829 hvc0     Ss+    0:00 /sbin/agetty --keep-baud 115200 38400 9600 hvc0 vt220

Doc

man systemd-getty-generator

 

 

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Kernal startup 資料:

 

在 /etc/default/grub 加入 Kernel Parmeter

GRUB_CMDLINE_LINUX="console=ttyS0,38400n8"

之後行

update-grub

 

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連接 console

 

virsh # console debian3

output:

Connected to domain debian3
Escape character is ^]             <--- ctrl + ]

Debian GNU/Linux 6.0 debian3 ttyS0

debian3 login:

Exit console

# * English keyboard

Keyboard: Ctrl+]

 

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Host pty

 

每一個 VM Guest 運行時, 那他的 console 都會對應 host 上的一個 pty

virsh # ttyconsole debian1

output:

/dev/pts/8

P.S.

當有 output 時, 亦即 VM有設定了 console port ( XML 設定)

    <console type='pty'>
      <target type='serial' port='0'/>
    </console>

virsh console DID 亦是連這個 port 的 !!

 

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VNC

 

查看某 VM Guest  的 VNC Port:

virsh # vncdisplay debian1

192.168.123.10:0

XML 設定:

<graphics type='vnc' port='-1' autoport='yes' listen='192.168.123.10' passwd='PW' keymap='en-us'/>

• 當 port='-1' autoport='yes': 在 5900 ~ 5999 之間找可用的 Port
• Default 只 listen 127.0.0.1

指定用那一個 port:

    <graphics type='vnc' port='5913' autoport='no' listen='192.168.123.10'/>

保存後會自動變成:

<devices>
    ...
    <graphics type='vnc' port='5913' autoport='no' listen='192.168.123.10'>
      <listen type='address' address='192.168.123.10'/>
    </graphics>
</devices>

Change VPN Port on Guest running:

qemu-monitor-command  <domain>  --hmp  change  vnc :65

• --hmp            command is in human monitor protocol

Chnage VNC Password:

qemu-monitor-command <domain>  --hmp  set_password  vnc  <YOUR_PW>

 

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