Debian 12: KVM Virtualization - creating guest (part 3)

To show available os for guest

$ virt-install --osinfo list | grep arch
archlinux

To create guest with name=guest01, disk size 10GB, Ram 2Gb (2048), virtual processor 2, os variant debian 12 (not available, we use debian11), boot from iso file: 

$ virt-install \
  --name guest01 \
  --memory 2048 \
  --vcpus 2 \
  --disk path=/home/dedetok/guests/guest01.qcoe2,size=10 \
  --cdrom /home/dedetok/Downloads/debian-12.11.0-amd64-netinst.iso \
  --nonetworks \
  --os-variant debian11 \
  --virt-type kvm

Parameters:

• --name: name to identify guest
• --ram: guest memory in megabytes
• --vcpus: number of cpu for guest
• --disk: path=<path_to_disk_image> , size=<disk_size_in_gb>
• --cdrom: install from iso file or CD/DVD/USB
• --nonetworks: no update or install from internet 
  or
  --network bridge=br0 to use bridge network, see part 2
  

Options:

1. Graphics option
   • --graphics vnc: Enables VNC for graphical access. If virt-viewer is installed, it will automatically launch. If not, you'll need to manually connect using a VNC client like vinagre or remmina.
   • --graphics spice: Enables SPICE for graphical access. SPICE is generally considered more modern and efficient than VNC.
   • --graphics none: Disables graphical access and forces a text-mode installation using the serial console.
2. Disk option
   • Default folder for virtual disk /var/lib/libvirt/images/
     qcow2 offers features that raw (or img) doesn't:
   1. Snapshots: qcow2 allows you to create snapshots of your virtual machine's disk, enabling easy rollback to previous states.
   2. Compression: It can compress the disk image, potentially saving storage space.
   3. Sparse files: qcow2 supports sparse files, meaning it only allocates disk space for used portions of the image, which can be more efficient.
   • raw format (or just img when using virt-install) has no special features:
     It simply represents the raw data of the disk, which can be less flexible and potentially wasteful of disk space.

list guest
$ virsh list --all

To start vm
$ virsh start guest01

to restart vm
$ virsh reboot guest01 --mode initctl

to force stoping vm
$ virsh destroy guest01

to force shutdown vm
$ virsh shutdown guest01 --mode acpi

to suspend vm
$ virsh suspend guest01

to resume vm after suspend
$ virsh resume guest01

to reset vm (similiar to pressing reset button on physical PC)
$ virsh reset guest01

Restarting KVM Daemon
# systemctl restart libvirtd

To show version
$ virsh version
Compiled against library: libvirt 9.0.0
Using library: libvirt 9.0.0
Using API: QEMU 9.0.0
Running hypervisor: QEMU 7.2.17

to remove vm and its storage permanently
$ virsh undefine --managed-save --remove-all-storage guest01

To make vm auto run after host restart (run once)
$ virsh autostart guest01

References:

• wiki.debian.org/KVM
• wiki.debian.org/DebianInstaller/Preseed

Debian: repair micro SD card command line

Detect your micro SD card

# dmesg
[  482.261836] scsi 1:0:0:0: Direct-Access     Multiple Card  Reader     1.00 PQ: 0 ANSI: 0
[  482.265756] sd 1:0:0:0: Attached scsi generic sg1 type 0
[  483.034812] sd 1:0:0:0: [sdb] 3911680 512-byte logical blocks: (2.00 GB/1.87 GiB)
[  483.036904] sd 1:0:0:0: [sdb] Write Protect is off
[  483.036931] sd 1:0:0:0: [sdb] Mode Sense: 03 00 00 00
[  483.038288] sd 1:0:0:0: [sdb] No Caching mode page found
[  483.038321] sd 1:0:0:0: [sdb] Assuming drive cache: write through
[  483.058653]  sdb: sdb1
[  483.066093] sd 1:0:0:0: [sdb] Attached SCSI removable disk
# lsblk
NAME   MAJ:MIN RM   SIZE RO TYPE MOUNTPOINT
sda      8:0    0 298.1G  0 disk
├─sda1   8:1    0 103.6G  0 part
├─sda2   8:2    0   450M  0 part
├─sda3   8:3    0     1K  0 part
├─sda5   8:5    0 120.2G  0 part
├─sda6   8:6    0     2G  0 part [SWAP]
└─sda7   8:7    0  71.8G  0 part /
sdb      8:16   1   1.9G  0 disk
└─sdb1   8:17   1   1.9G  0 part 

Repair file system micro SD card

# umount /dev/sdb1
umount: /dev/sdb1: not mounted.
# umount /dev/sdb
umount: /dev/sdb: not mounted.
# fsck.vfat -a -w /dev/sdb1

option:

• -a : automatic repair filesystem
• -w : write change immediately

Format if there is no data you can saved and you want fresh storage in micro SD card 

# mkfs.vfat /dev/sdb1
mkfs.fat 4.2 (2021-01-31)

Debian 12: KVM Virtualization - configure bridge network in host (part 2)

By default, KVM Guest will able to use host connection to connect to lan and internet, but not vice versa.

To make host, guest and lan accessible each other, on network configuration we can use is bridging.

Install bridge-util 

# apt-get install bridge-utils
Reading package lists... Done
Building dependency tree... Done
Reading state information... Done
The following NEW packages will be installed:
    bridge-utils
...

Configuring bridge

create bridge interface

# brctl addbr br0

show existing infterface

# ip addre show
1: lo: ...
2: enp2s0: ... -> this is lan
3: wlo1: ...-> this is wifi and not supported
4: br0: ...

add interface to bridge

# brctl addif br0 enp2s0 


make it persistence, edit /etc/network/interface

...
# The loopback network interface
auto lo
iface lo inet loopback

# set interface manually, avoid conflict with network manager
iface enp2s0 inet manual
iface wlo1 inet manual

# bridge setup
# dhcp
# avoid conflict with network manager
#auto br0
iface br0 inet dhcp
   bridge_ports enp2s0
# for manual ipv4
# iface bro inet static
#   bridge_ports enp2s0
#   address 1192.168.1.2
#   broadcast 192.168.1.255
#   netmask 255.255.255.0
#   gateway 192.169.1.1

restart networking service

# systemctl restart networking


To make NetworkManager manage your network edit  /etc/NetworkManager/NetworkManager.conf, make sure managed=true

[main]
plugins=ifupdown,keyfile

[ifupdown]
#managed=false
managed=true


Reference:
wiki.debian.org/BridgeNetworkConnections

Writing math equation in web using mathjax and latex

Add the mathjax javascript library to the head or body of the html

<script async="" id="MathJax-script" src="https://cdn.jsdelivr.net/npm/mathjax@3/es5/tex-chtml.js" type="text/javascript">
</script>

To declare math equation use identifier 
\ (...\) for inline or 
\ [...\] for display

Note: no space between \ ( and \ [  

Example to write 1/2 

in latex: \ frac{1}{2}

in mathjax html (e.q. blogspot): \ ( \ frac{1}{2}\) 

Note: no space between characters above

result 

\(\frac{1}{2}\)

 

If you copy paste from word application with math equation support, the code may become messy, e.q word equation will result in many additional custom html tag. 

Trigonometric Identities

 

Trigonometric Identities

 Common degree

degree	Sin	Cos	Tg
0	0	1	0
30 or π/6
45 or π/4			1
60 or π/3
90 or π/2	1	0	infinite

 Reciprocal Trigonometric Identities

  ;    ; 

  ;   ;

 

 

Pythagorean Trigonometric Identities

 

Ratio Trigonometric Identities

 

Trigonometric Identities of Opposite Angles

 

Sin (-a) = – Sin a

Cos (-a) = Cos a

Tan (-a) = – Tan a

Cot (-a) = – Cot a

Sec (-a) = Sec a

Csc (-a) = -Csc a

 

Trigonometric Identities of Complementary Angles

 

Sin (90 – a) = Cos a

Cos (90 – a) = Sin a

Tan (90 – a) = Cot a

Cot ( 90 – a) = Tan a

Sec (90 – a) = Csc a

Csc (90 – a) = Sec a

 

Trigonometric Identities of Supplementary Angles

 

sin (180°- a) = sina

cos (180°- a) = -cos a

cosec (180°- a) = cosec a

sec (180°- a) = -sec a

tan (180°- a) = -tan a

cot (180°- a) = -cot a

 

Sum and Difference of Angles Trigonometric Identities

 

 

Double Angle Trigonometric Identities

 

 

Half Angle Identities

 

 

 

Product-Sum Trigonometric Identities

 

 

 

 

Trigonometric Identities of Products

 

 

 

byjus.com/maths/trigonometric-identities/