How would you set the boot order on KVM when using libvirt/virsh? (Either via config or command)
Please take a look at the section Operation System booting.
The most common option is the BIOS bootloader where it allows you specifying boot order via changing domain XML. try command virsh edit <your-domain-name> then adjust the boot order with this example (copied from libvirt.org):
<os>
<type>hvm</type>
<loader>/usr/lib/xen/boot/hvmloader</loader>
<boot dev='network'/>
<boot dev='cdrom'/>
<boot dev='hd'/>
<bootmenu enable='yes'/>
</os>
Which means the boot order is:
boot from network like PXE boot
boot from CD-ROM if no PXE boot
boot from local hard disk if no PXE boot nor bootable CD
If you have multiple hard disks a better solution is to use
<boot order='1'/>
for the first device you want to boot and
<boot order='2'/>
for the 2nd etc
For more information see https://libvirt.org/formatdomain.html#elementsDisks
Related
I have a Yocto based OS on which I have everything installed to start the network.
Nevertheless, at each boot I need to do systemctl start networking to start it. Initially the service was even masked. I found out how to unmask it but I can't find a way to start it automatically.
I don't know much about systemd but the networking.service is located in generator.late folder. From what I understood, it's generated afterward.
How can I enable it?
It depends if you want to enable the service only on one particular device. If yes, it is simple:
systemctl enable networking
Append the parameter --now if you also want to start the service just now.
If you want to enable the service on all your devices (i.e. it will be automatically enabled in all your images coming from build), the best way is to extend the recipe, but please see below for other ways how to handle the network. The process is describe at NXP support for example.
Some notes about networking.service itself: I assume that your networking.service comes from init-ifupdown recipe. If yes, is there any reason to handle network configuration using old SysV init script in system with systemd? The service is generated from SysV init script by systemd-sysv-generator. So I would suggest to try other networking services like systemd's native "systemd-networkd", "NetworkManager" or "connman". The best choice depends on type of your embedded systemd. These services are integrated with systemd much better.
Some more information on activating or enabling the services: https://unix.stackexchange.com/questions/302261/systemd-unit-activate-vs-enable
In a single processor system, when powered on the processor starts executing the boot rom code and the multiple stages of the boot. However how does this work in a multi process system? Does one processor act as the master? Who decides which processor is the master and the others helpers?
How and where is it configured?
Are the page tables shared between the processors? The processor caches are obviously different, at least the L1 caches is.
Multiprocessor Booting
1 One processor designated as ‘Boot Processor’ (BSP)
– Designation done either by Hardware or BIOS
– All other processors are designated AP (Application Processors)
2- BIOS boots the BSP
3- BSP learns system configuration
4- BSP triggers boot of other AP
– Done by sending an Startup IPI (inter processor interrupt) signal to
the AP
look here
and here for more details
Got a general question about load balancing setup in JBoss (7.1.1.Final). I'm trying to setup a clustered JBoss instance with a master and slave node and I'm using the demo app here (https://docs.jboss.org/author/display/AS72/AS7+Cluster+Howto) to prove the load balancing/session replication. I've basically followed through to just before the 'cluster configuration' section.
I've got the app deployed to the master and slave nodes and if I hit their individual IPs directly I can access the application fine. According to the JBoss logs and admin console the slave has successfully connected to the master. However, if I put something in the session on the slave, take the slave offline, the master cannot read the item that the slave put in the session.
This is where I need some help with the general setup. Do I have to have a separate apache httpd instance sat in front of JBoss to do the load balancing? I thought there was a load balancing capability built into JBoss that wouldn't need the separate server, or am I just completely wrong? If I don't need apache, please could you point me in the direction of instructions to setup the JBoss load balancing?
Thanks.
Yes, you need a Apache or any other software or hardware that allows you to perform load balancing of the HTTP request JBoss Application Server does not provide this functionality.
For proper operation of the session replication you should check that the server configuration and the application configuration is well defined.
On the server must have the cache enabled for session replication (you can use standalone-ha.xml or standalone-full-ha.xml file for initial config).
To configuring the application to replicate the HTTP session is done by adding the <distributable/> element to the web.xml.
You can see a full example in http://blog.akquinet.de/2012/06/21/clustering-in-jboss-as7eap-6/
The application stack I want to dockerize shall run within a CentOS container. The installation procedure verifies kernel version to ensure application requirements are met. Currently it is detected using "uname ...".
However the application now detects the host kernel version, which is "UBUNTU ..." and not "CentOS" ..."
Is it possible to detect the container's kernel version?
Thanks.
In fact, the kernel is the same in the host and in the container. That's the very principle of containerization: the kernel is shared (because actually, a container is a collection of processes running on top of the host kernel, with special isolation properties).
Does that pose a problem for your application?
Where in the boot process does the "scheduler" get created and when created how can its instructions be accessed?
That depends on the OS you use, but several things should be clear:
before the first switch to userland
before any kernel threads are started or any other multi-programming (multi-tasking) is done
Obviously that is relatively early in the boot process.
What exactly do you mean by "how can its instructions be accessed?"?
the default scheduler is set in kernel config :
adrian#adrian: ~ $ grep cfq /boot/config-2.6.36.2-desktop-2mnb
CONFIG_DEFAULT_IOSCHED="cfq"
at boot time you can do in the kernel line as example:
kernel /vmlinuz-2.6.18-8.el5 ro root=/dev/sda2 elevator=deadline