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.
root@ajung1215b:~# 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
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/