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Why my 500GB Hard disk shows less size when formatted on the system ?

There are two ways to define a gigabyte.  One is vendor way and another one is the computer's binary powers of two definition method.

When you buy a "500 Gigabyte" hard drive, the vendor defines it using the decimal powers of ten definition of the "Giga" prefix.


500 * 109 bytes = 500,000,000,000 = 500 GigabytesBut the computers operating system determines the size of the drive using the computer's binary powers of two definitions of the "Giga" prefix:


465 * 230 bytes = 499,289,948,160 = 465 Gigabytes/ GibibytesIf you're wondering where 35 Gigabytes of your 500 Gigabyte drive just disappeared too, you're not alone. It's an old trick by hard drive makers -- they intentionally use the official SI definitions of the Giga prefix so they can inflate the sizes of their hard drives, at least on paper.  Ideally, we should refer to binary prefix when calculating sizes of storage devices as this makes more sense. Following tables helps you in unders…
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What are the useful nvram settings in macOS ?

The OS X boot arguments are useful for troubleshooting problems with system startup and how the system behaves when running.
sudo nvram boot-args="-v" : This command will set the system to always boot to verbose mode, so we do not need to hold Command + V at system startup.
sudo nvram boot-args="-x" : This will set the system to always boot into Safe Mode.
sudo nvram boot-args="-s" : This command will boot the system into single user mode without needing to hold Command-S at system startup.
sudo nvram boot-args="iog=0x0"  :  when you close the display but connect the system to an external monitor and keyboard the system will stay awake. After running this command, when connecting an external monitor, the internal display will be disabled, which can be beneficial in some situations such as those where you are mirroring your desktop but wish to run the external display at a higher resolution than your laptop can run.sudo nvram boot-args="debug=0x…

How to rename GIT tags ?

Sometimes we might need to rename the GIT tags , this can be easily achieved by following these steps using GIT command line tool.
git tag new-tag old-tag git tag -d old-tag git push origin :refs/tags/old-tag git push --tags

How to check user and group associations on macOS

Sometimes we might have to know the list of users, groups and ids such as userid and groupid on macOS system. There are several ways to find this information. 

dsacacheutil:
The command dscacheutil -q groupwill output all groups with their name, ID numbers, and list of members. The command dscacheutil -q userwill output name,uid, gid, dir, shell, gecos details.
Note:  The above command will output all the groups and user details, including built-in system ones mortals were never meant to see.
Check user and group association:
We can run below command to check user and group associations to know whether a user belongs to a group or not.


dsmemberutil checkmembership -u 501 -g 1
user is not a member of the group

Or

dsmemberutil checkmembership -U user -G staff
The user user cannot be found There was an unknown error. User not found



Alternative methods to find group and user details on macOS
To list users in mac:
dscl . list /Users

To list groups in mac:
dscl . list /Groups


To list by group id:
dscl . list …

How to enable 64 bit testing mode in macOS Mojave 10.14

One can use 64-bit testing mode in macOS 10.14 to test software for 64-bit compatibility.


To enable the 64-bit testing mode: Boot to Recovery OS by restarting your machine and holding down the Command and R keys at startup. Launch Terminal Execute the following command: nvram boot-args="-no32exec" Restart the machine     
Note: The 64-bit testing mode prevents 32-bit processes from launching. Launching an app that depends on 32-bit software results in a notification that the application can't be opened. 


To disable the 64-bit testing mode: Boot to Recovery OS by restarting your machine and holding down the Command and R keys at startup. Launch Terminal Execute the following command: nvram boot-args="" Restart the machine 

How to get a certificate fingerprint as SHA-256, SHA-1 or MD5 using OpenSSL on mac

As per my old post ( http://anandmpandit.blogspot.in/2016/11/how-to-extract-signing-certificates.html ) , we can extract the binary signing certificates on mac using codesign tool. If you needed to get fingerprint details of the certificate in MD5, SHA1 or SHA256 format then you have run below steps on the extracted certificate file on macOS.


SHA256:

SHA256 Fingerprint=D3:0A:32:6C:77:77:93:B5:45:20:AC:C0:D4:7E:3A:84:34:50:96:54:08:7F:7D:63:4C:3E:06:3B:E8:1F:C1:90


SHA1:

SHA1 Fingerprint=BF:2C:93:1F:BD:88:E5:4C:96:D8:86:D5:F1:E6:9B:B7:DE:76:51:62

MD5:

MD5 Fingerprint=3C:A3:3B:76:6D:AE:3F:4B:4E:B2:AA:66:97:55:B8:76

How to boot into recovery mode on mac without holding Command + R Key on keyboard ?

Generally well known method to boot the mac into recovery mode is by holding the Command + R on keyboard while mac is turned on. However you can force the mac to boot into recovery mode upon next reboot by changing the nvram setting. To do that, Run below command.  

sudo nvram "recovery-boot-mode=unused" sudo reboot