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In this short tutorial, I am going to show you some basic command line commands in Microsoft Windows, and their equivalent commands in Apple Mac OS Terminal. This is by no means a complete reference to the available commands, just a short list of some common commands available to you on your operating system. Jul 11, 2017 How the Command and Option Keys Work on a Mac The Command Key. The Command key doesn't do anything on its own. It's a modifier key you can press to issue keyboard. The Option key functions similarly to the AltGr key on many PC keyboards, which explains why it also has.

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Historically, the command line interface provided a way to manipulate a computer over simple, text-based connections. In the modern era, in spite of the ability to transmit graphical user interfaces over the Internet, the command line remains a powerful tool for performing certain types of tasks.

As described previously in Before You Begin, most users interact with a command-line environment using the Terminal application, though you may also use a remote connection method such as secure shell (SSH). Each Terminal window or SSH connection provides access to the input and output of a shell process. A shell is a special command-line tool that is designed specifically to provide text-based interactive control over other command-line tools.

In addition to running individual tools, most shells provide some means of combining multiple tools into structured programs, called shell scripts (the subject of this book).

Different shells feature slightly different capabilities and scripting syntax. https://coolzfil977.weebly.com/icircuit-1-7-download-free.html. Although you can use any shell of your choice, the examples in this book assume that you are using the standard OS X shell. The standard shell is bash if you are running OS X v10.3 or later and tcsh if you are running an earlier version of the operating system.

The following sections provide some basic information and tips about using the command-line interface more effectively; they are not intended as an exhaustive reference for using the shell environments.

Note: This appendix was originally part of Mac Technology Overview.

Basic Shell Concepts

Before you start working in any shell environment, there are some basic features of shell scripting that you should understand. Some of these features are specific to OS X, but most are common to all platforms that support shell scripting.

Running Your First Command-Line Tool

In general, you run command-line tools that OS X provides by typing the name of the tool. (The syntax for running tools that you've added is described later in this appendix.)

For example, if you run the ls command, by default, it lists the files in your home directory. To run this command, type ls and press Return.

Most tools also can take a number of flags (sometimes called switches). For example, you can get a 'long' file listing (with additional information about every file) by typing ls -l and pressing Return. The -l flag tells the ls command to change its default behavior.

Similarly, most tools take arguments. For example, to show a long listing of the files on your OS X desktop, type ls -l Desktop and press Return. In that command, the word Desktop is an argument that is the name of the folder that contains the contents of your OS X desktop.

In addition, some tools have flags that take flag-specific arguments in addition to the main arguments to the tool as a whole.

Specifying Files and Directories

Most commands in the shell operate on files and directories, the locations of which are identified by paths. The directory names that make up a path are separated by forward-slash characters. For example, the Terminal program is in the Utilities folder within the Applications folder at the top level of your hard drive. Its path is /Applications/Utilities/Terminal.app.

The shell (along with, for that matter, all other UNIX applications and tools) also has a notion of a current working directory. When you specify a filename or path that does not start with a slash, that path is assumed to be relative to this directory. For example, if you type cat foo, the cat command prints the contents of the file foo in the current directory. You can change the current directory using the cd command.

Finally, the shell supports a number of directory names that have a special meaning.

Table A-1 lists some of the standard shortcuts used to represent specific directories in the system. Because they are based on context, these shortcuts eliminate the need to type full paths in many situations.

File and directory names traditionally include only letters, numbers, hyphens, the underscore character (_), and often a period (.) followed by a file extension that indicates the type of file (.txt, for example). Most other characters, including space characters, should be avoided because they have special meaning to the shell.

Although some OS X file systems permit the use of these other characters, including spaces, you must do one of the following:

• 'Escape' the character—put a backslash character () immediately before the character in the path.

• Add single or double quotation marks around the path or the portion that contains the offending characters.

For example, the path name My Disk can be written as 'My Disk', 'My Disk', or My Disk.

Single quotes are safer than double quotes because the shell does not do any interpretation of the contents of a single-quoted string. However, double quotes are less likely to appear in a filename, making them slightly easier to use. When in doubt, use a backslash before the character in question, or two backslashes to represent a literal backslash.

For more detailed information, see Quoting Special Characters in Flow Control, Expansion, and Parsing.

Accessing Files on Additional Volumes

On a typical UNIX system, the storage provided by local disk drives is presented as a single tree of files descending from a single root directory. This differs from the way the Finder presents local disk drives, which is as one or more volumes, with each volume acting as the root of its own directory hierarchy. To satisfy both worlds, OS X includes a hidden directory, Volumes, at the root of the local file system. This directory contains all of the volumes attached to the local computer.

To access the contents of other local (and many network) volumes, you prefix the volume-relative path with /Volumes/ followed by the volume name. For example, to access the Applications directory on a volume named MacOSX, you would use the path /Volumes/MacOSX/Applications.

Note: To access files on the boot volume, you are not required to add volume information, since the root directory of the boot volume is /. Including the volume information still works, though, so if you are interacting with the shell from an application that is volume-aware, you may want to add it, if only to be consistent with the way you access other volumes. You must include the volume information for all volumes other than the boot volume.

Input And Output

Most tools take text input from the user and print text out to the user's screen. They do so using three standard file descriptors, which are created by the shell and are inherited by the program automatically. These standard file descriptors are listed in Table A-2.

To learn more about working with these descriptors, including redirecting the output of one tool to the input of another, read Shell Input and Output.

Terminating Programs

To terminate the currently running program from the command line, press Control-C. This keyboard shortcut sends an abort (ABRT) signal to the currently running process. In most cases this causes the process to terminate, although some tools may install signal handlers to trap this signal and respond differently. (See Trapping Signals in Advanced Techniques for details.)

In addition, you can terminate most scripts and command-line tools by closing a Terminal window or SSH connection. This sends a hangup (HUP) signal to the shell, which it then passes on to the currently running program. If you want a program to continue running after you log out, you should run it using the nohup command, which catches that signal and does not pass it on to whatever command it invokes.

Frequently Used Commands

Shell scripting involves a mixture of built-in shell commands and standard programs that run in all shells. Although most shells offer the same basic set of commands, there are often variations in the syntax and behavior of those commands. In addition to the shell commands, OS X also provides a set of standard programs that run in all shells.

Table A-3 lists some commands that are commonly used interactively in the shell. Most of the items in this table are not specific to any given shell. For syntax and usage information for each command, see the corresponding man page. For a more in-depth list of commands and their accompanying documentation, see OS X Man Pages.

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Environment Variables

Some programs require the use of environment variables for their execution. Environment variables are variables inherited by all programs executed in the shell's context. The shell itself uses environment variables to store information such as the name of the current user, the name of the host computer, and the paths to any executable programs. You can also create environment variables and use them to control the behavior of your program without modifying the program itself. For example, you might use an environment variable to tell your program to print debug information to the console.

To set the value of an environment variable, you use the appropriate shell command to associate a variable name with a value. For example, to set the environment variable MYFUNCTION to the value MyGetData in the global shell environment you would type the following command in a Terminal window:

When you launch an application from a shell, the application inherits much of its parent shell's environment, including any exported environment variables. This form of inheritance can be a useful way to configure the application dynamically. For example, your application can check for the presence (or value) of an environment variable and change its behavior accordingly. Different shells support different semantics for exporting environment variables, so see the man page for your preferred shell for further information.

Child processes of a shell inherit a copy of the environment of that shell. Shells do not share their environments with one another. Thus, variables you set in one Terminal window are not set in other Terminal windows. Once you close a Terminal window, any variables you set in that window are gone.

If you want the value of a variable to persist between sessions and in all Terminal windows, you must either add it to a login script or add it to your environment property list. See Before You Begin for details.

Similarly, environment variables set by tools or subshells are lost when those tools or subshells exit.

Running User-Added Commands

As mentioned previously, you can run most tools by typing their name. This is because those tools are located in specific directories that the shell searches when you type the name of a command. The shell uses the PATH environment variable to control where it searches for these tools. It contains a colon-delimited list of paths to search—/usr/bin:/bin:/usr/sbin:/sbin, for example.

If a tool is in any other directory, you must provide a path for the program to tell it where to find that tool. (For security reasons, when writing scripts, you should always specify a complete, absolute path.)

For security reasons, the current working directory is not part of the default search path (PATH), and should not be added to it. If it were, then another user on a multi-user system could trick you into running a command by adding a malicious tool with the same name as one you would typically run (such as the ls command) or a common misspelling thereof.

For this reason, if you need to run a tool in the current working directory, you must explicitly specify its path, either as an absolute path (starting from /) or as a relative path starting with a directory name (which can be the . directory). For example, to run the MyCommandLineProgram tool in the current directory, you could type ./MyCommandLineProgram and press Return.

With the aforementioned security caveats in mind, you can add new parts (temporarily) to the value of the PATH environment variable by doing the following:

If you want the additional path components to persist between sessions and in all Terminal windows, you must either add it to a login script or add it to your environment property list. See Before You Begin for details.

Running Applications

To launch an application, you can generally either:

• Use the open command.

• Run the application binary itself.

  Type the pathname of the executable file inside the package.

Note: As a general rule, if you launch a GUI application from a script, you should run that script only within Terminal or another GUI application. You cannot necessarily launch an GUI application when logged in remotely (using SSH, for example). In general, doing so is possible only if you are also logged in using the OS X GUI, and in some versions of OS X, it is disallowed entirely.

Learning About Other Commands

At the command-line level, most documentation comes in the form of man pages (short for manual). Man pages provide reference information for many shell commands, programs, and POSIX-level concepts. The manual page manpages describes the organization of manual, and the format and syntax of individual man pages.

To access a man page, type the man command followed by the name of the thing you want to look up. For example, to look up information about the bash shell, you would type man bash. The man pages are also included in the OS X Developer Library (OS X Man Pages).

You can also search the manual pages by keyword using the apropos command.

Note: Not all commands and programs have man pages. For a list of available man pages, look in the /usr/share/man directory or see OS X Man Pages in the OS X Developer Library.

Most shells have a command or man page that displays the list of commands that are built into the shell (builtins). Table A-4 lists the available shells in OS X along with the ways you can access the list of builtins for the shell.

Basic Shell Concepts

Before you start working in any shell environment, there are some basic features of shell scripting that you should understand. Some of these features are specific to OS X, but most are common to all platforms that support shell scripting.

Running Your First Command-Line Tool

In general, you run command-line tools that OS X provides by typing the name of the tool. (The syntax for running tools that you've added is described later in this appendix.)

For example, if you run the ls command, by default, it lists the files in your home directory. To run this command, type ls and press Return.

Most tools also can take a number of flags (sometimes called switches). For example, you can get a 'long' file listing (with additional information about every file) by typing ls -l and pressing Return. The -l flag tells the ls command to change its default behavior.

Similarly, most tools take arguments. For example, to show a long listing of the files on your OS X desktop, type ls -l Desktop and press Return. In that command, the word Desktop is an argument that is the name of the folder that contains the contents of your OS X desktop.

In addition, some tools have flags that take flag-specific arguments in addition to the main arguments to the tool as a whole.

Specifying Files and Directories

Most commands in the shell operate on files and directories, the locations of which are identified by paths. The directory names that make up a path are separated by forward-slash characters. For example, the Terminal program is in the Utilities folder within the Applications folder at the top level of your hard drive. Its path is /Applications/Utilities/Terminal.app.

The shell (along with, for that matter, all other UNIX applications and tools) also has a notion of a current working directory. When you specify a filename or path that does not start with a slash, that path is assumed to be relative to this directory. For example, if you type cat foo, the cat command prints the contents of the file foo in the current directory. You can change the current directory using the cd command.

Finally, the shell supports a number of directory names that have a special meaning.

Table A-1 lists some of the standard shortcuts used to represent specific directories in the system. Because they are based on context, these shortcuts eliminate the need to type full paths in many situations.

File and directory names traditionally include only letters, numbers, hyphens, the underscore character (_), and often a period (.) followed by a file extension that indicates the type of file (.txt, for example). Most other characters, including space characters, should be avoided because they have special meaning to the shell.

Although some OS X file systems permit the use of these other characters, including spaces, you must do one of the following:

• 'Escape' the character—put a backslash character () immediately before the character in the path.

• Add single or double quotation marks around the path or the portion that contains the offending characters.

For example, the path name My Disk can be written as 'My Disk', 'My Disk', or My Disk.

Single quotes are safer than double quotes because the shell does not do any interpretation of the contents of a single-quoted string. However, double quotes are less likely to appear in a filename, making them slightly easier to use. When in doubt, use a backslash before the character in question, or two backslashes to represent a literal backslash.

For more detailed information, see Quoting Special Characters in Flow Control, Expansion, and Parsing.

Accessing Files on Additional Volumes

On a typical UNIX system, the storage provided by local disk drives is presented as a single tree of files descending from a single root directory. This differs from the way the Finder presents local disk drives, which is as one or more volumes, with each volume acting as the root of its own directory hierarchy. To satisfy both worlds, OS X includes a hidden directory, Volumes, at the root of the local file system. This directory contains all of the volumes attached to the local computer.

To access the contents of other local (and many network) volumes, you prefix the volume-relative path with /Volumes/ followed by the volume name. For example, to access the Applications directory on a volume named MacOSX, you would use the path /Volumes/MacOSX/Applications.

Note: To access files on the boot volume, you are not required to add volume information, since the root directory of the boot volume is /. Including the volume information still works, though, so if you are interacting with the shell from an application that is volume-aware, you may want to add it, if only to be consistent with the way you access other volumes. You must include the volume information for all volumes other than the boot volume.

Input And Output

Most tools take text input from the user and print text out to the user's screen. They do so using three standard file descriptors, which are created by the shell and are inherited by the program automatically. These standard file descriptors are listed in Table A-2.

To learn more about working with these descriptors, including redirecting the output of one tool to the input of another, read Shell Input and Output.

Terminating Programs

To terminate the currently running program from the command line, press Control-C. This keyboard shortcut sends an abort (ABRT) signal to the currently running process. In most cases this causes the process to terminate, although some tools may install signal handlers to trap this signal and respond differently. (See Trapping Signals in Advanced Techniques for details.)

In addition, you can terminate most scripts and command-line tools by closing a Terminal window or SSH connection. This sends a hangup (HUP) signal to the shell, which it then passes on to the currently running program. If you want a program to continue running after you log out, you should run it using the nohup command, which catches that signal and does not pass it on to whatever command it invokes.

Frequently Used Commands

Shell scripting involves a mixture of built-in shell commands and standard programs that run in all shells. Although most shells offer the same basic set of commands, there are often variations in the syntax and behavior of those commands. In addition to the shell commands, OS X also provides a set of standard programs that run in all shells.

Table A-3 lists some commands that are commonly used interactively in the shell. Most of the items in this table are not specific to any given shell. For syntax and usage information for each command, see the corresponding man page. For a more in-depth list of commands and their accompanying documentation, see OS X Man Pages.

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Environment Variables

Some programs require the use of environment variables for their execution. Environment variables are variables inherited by all programs executed in the shell's context. The shell itself uses environment variables to store information such as the name of the current user, the name of the host computer, and the paths to any executable programs. You can also create environment variables and use them to control the behavior of your program without modifying the program itself. For example, you might use an environment variable to tell your program to print debug information to the console.

To set the value of an environment variable, you use the appropriate shell command to associate a variable name with a value. For example, to set the environment variable MYFUNCTION to the value MyGetData in the global shell environment you would type the following command in a Terminal window:

When you launch an application from a shell, the application inherits much of its parent shell's environment, including any exported environment variables. This form of inheritance can be a useful way to configure the application dynamically. For example, your application can check for the presence (or value) of an environment variable and change its behavior accordingly. Different shells support different semantics for exporting environment variables, so see the man page for your preferred shell for further information.

Child processes of a shell inherit a copy of the environment of that shell. Shells do not share their environments with one another. Thus, variables you set in one Terminal window are not set in other Terminal windows. Once you close a Terminal window, any variables you set in that window are gone.

If you want the value of a variable to persist between sessions and in all Terminal windows, you must either add it to a login script or add it to your environment property list. See Before You Begin for details.

Similarly, environment variables set by tools or subshells are lost when those tools or subshells exit.

Running User-Added Commands

As mentioned previously, you can run most tools by typing their name. This is because those tools are located in specific directories that the shell searches when you type the name of a command. The shell uses the PATH environment variable to control where it searches for these tools. It contains a colon-delimited list of paths to search—/usr/bin:/bin:/usr/sbin:/sbin, for example.

If a tool is in any other directory, you must provide a path for the program to tell it where to find that tool. (For security reasons, when writing scripts, you should always specify a complete, absolute path.)

For security reasons, the current working directory is not part of the default search path (PATH), and should not be added to it. If it were, then another user on a multi-user system could trick you into running a command by adding a malicious tool with the same name as one you would typically run (such as the ls command) or a common misspelling thereof.

For this reason, if you need to run a tool in the current working directory, you must explicitly specify its path, either as an absolute path (starting from /) or as a relative path starting with a directory name (which can be the . directory). For example, to run the MyCommandLineProgram tool in the current directory, you could type ./MyCommandLineProgram and press Return.

With the aforementioned security caveats in mind, you can add new parts (temporarily) to the value of the PATH environment variable by doing the following:

If you want the additional path components to persist between sessions and in all Terminal windows, you must either add it to a login script or add it to your environment property list. See Before You Begin for details.

Running Applications

To launch an application, you can generally either:

• Use the open command.

• Run the application binary itself.

  Type the pathname of the executable file inside the package.

Note: As a general rule, if you launch a GUI application from a script, you should run that script only within Terminal or another GUI application. You cannot necessarily launch an GUI application when logged in remotely (using SSH, for example). In general, doing so is possible only if you are also logged in using the OS X GUI, and in some versions of OS X, it is disallowed entirely.

Learning About Other Commands

At the command-line level, most documentation comes in the form of man pages (short for manual). Man pages provide reference information for many shell commands, programs, and POSIX-level concepts. The manual page manpages describes the organization of manual, and the format and syntax of individual man pages.

To access a man page, type the man command followed by the name of the thing you want to look up. For example, to look up information about the bash shell, you would type man bash. The man pages are also included in the OS X Developer Library (OS X Man Pages).

You can also search the manual pages by keyword using the apropos command.

Note: Not all commands and programs have man pages. For a list of available man pages, look in the /usr/share/man directory or see OS X Man Pages in the OS X Developer Library.

Most shells have a command or man page that displays the list of commands that are built into the shell (builtins). Table A-4 lists the available shells in OS X along with the ways you can access the list of builtins for the shell.

Copyright © 2003, 2014 Apple Inc. All Rights Reserved. Terms of Use | Privacy Policy | Updated: 2014-03-10

When your computer encounters a serious problem that normal troubleshooting methods can't fix, you can try installing a fresh copy of your macOS to resolve it. If you want to install the latest macOS version that was previously installed on your computer, just press Command + R when restarting your Mac to pull up the macOS Recovery dialog.

But what happens when the Command + R shortcut doesn't work? You can still access your macOS Recovery options, but it's going to be a bit more complicated. This guide will teach you how to reinstall your macOS even if Mac Recovery Mode is not working on your MacBook.

But first, it is important to understand the reasons why the Command + R shortcut may not work.

Reasons Why Command R Is Not Working on Macbook

There are a few reasons why the Command + R combination may not work on your computer, such as:

• Age of your Mac – If you're using a Mac that's still running OS X Snow Leopard or older operating system, then your version doesn't have Recovery Mode. This feature was introduced with the release of OS X Lion in 2011 to allow users to diagnose hardware features and troubleshoot common Mac problems on startup.
• macOS version – If your macOS version is older than Sierra, then the Recovery options you have may not be the same as those running newer versions.
• Faulty keyboard – It is possible that your letter keys are not working.
• Corrupted recovery partition – Your recovery partition may have been corrupted or deleted.

Before we discuss how to access your Recovery mode when Command + R is not working on Macbook, let's first talk about what this mode is and its functions.

What Is MacBook Recovery Mode?

Not all Mac users know what the Recovery Mode is and what it is for. Many users don't even know this feature exists. To put it simply, the Recovery Mode is a dedicated partition on your hard drive housing a recovery image and a copy of your macOS installer. This partition is completely independent from the other partitions on your disk that even if you wipe your hard drive clean, it would still be there.

The recovery partition is helpful in extreme cases where you might need to reinstall a fresh copy of your latest macOS or OS X. Even if you format your drive and start from scratch, this partition remains intact and you can still reinstall your macOS, restore from a Time Machine backup , or repair your disk via Recovery Mode.

The Recovery Mode makes troubleshooting a lot easier and faster because all you need to do is press two keys: Command + R. But before you proceed with the solutions below, make sure to back up all your important files and optimize your Mac using an app such as Tweakbit MacRepair.

How to Check if Your Mac's Recovery Partition is Working

The first thing you need to rule out is whether you actually have a recovery partition and if it is working fine.

To boot into your Recovery Drive, follow these instructions:

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1. Shut down your Mac by clicking the Apple menu and choosing Shut Down.
2. Once the computer is turned off, hold down Command + R, then press the Power button.
3. Keep holding the Command + R keys until the Apple logo appears. Let go of the keys and wait for the startup process to complete. This may take longer than your usual boot up process, but don't worry because it's just loading items from your recovery partition.
4. When you see the macOS Utilities window or OS X Utilities for older Macs, then it means your recovery partition is working.

But if your Mac boots into the regular login window or just loads a blank screen, then you don't have a recovery partition.

You can also use Terminal to verify if you have a recovery partition by following the steps below:

1. Launch Terminal via Utilities folder or Spotlight search.
2. Type in diskutil list. This will show you a list of all the volumes and partitions on your Mac.

Look for drive with Boot Recovery HD in its name because that's your recovery partition. If you see it on the list but can't boot into it for some reason, then the drive could be corrupted. If it's not on the list, then the drive could have been deleted or you never had it in the first place.

Let's look at some of the things you can do when Mac Recovery Mode is not working on MacBook.

Method 1: Use Internet Recovery to Reinstall macOS

If you have a corrupted or missing recovery partition, you can still reinstall your macOS or OS X via the Utilities tool. This feature is available for newer Macs, and it allows you to boot directly from an internet connection even without a recovery partition.

To use macOS Internet Recovery:

1. Shut down your Mac by clicking the Apple logo > Shut Down.
2. Hold down the Command + Option/Alt-R keys, then press the Power button.
3. Let go of the keys when you see the spinning globe and the message 'Starting Internet Recovery. This may take a while.'
4. A progress bar will appear after this message. Wait for it to complete and for the macOS Utilities window to appear.
5. Click Reinstall macOS from the options that appear and follow the on-screen instructions.

Take note that Internet Recovery only works with networks using WEP and WPA security. If your network is using a different protocol, we suggest you connect to one that is compatible with the Internet Recovery feature because this method, by far, is the easiest way to reinstall your macOS.

Method 2: Create a USB macOS Bootable Installer

Command-K - Connect To Server Not Working…

If you have no access to Internet Recovery, you can try creating a bootable macOS installer using a flash drive. You need one with at least 12GB in storage. If you're using an existing flash drive, make sure to back up all the files in it because this process completely erases all the content of the USB.

The easiest way to create a USB macOS installer is via Terminal. But first, you need to locate the Install files for the macOS version you want to install. Go to your Applications folder and look for the installer files, or you can get them from your Mac App Store under the Purchased tab.

Once you have downloaded the installer, follow these steps to create your bootable drive:

1. Connect your flash drive to your computer.
2. Launch Disk Utility and select your flash drive. This should be listed under External in the sidebar .
3. Click Erase.
4. Once the drive has been erased, you'll see that the name of the drive has been changed to Untitled.
5. Launch Terminal and copy the following command, depending on the version you want to reinstall:
   • Mojave: sudo /Applications/Install macOS Mojave Beta.app/Contents/Resources/createinstallmedia –volume /Volumes/USB –nointeraction –downloadassets
   • High Sierra: sudo /Applications/Install macOS High Sierra.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install macOS High Sierra.app
   • Sierra: sudo /Applications/Install macOS Sierra.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install macOS Sierra.app
   • El Capitan: sudo /Applications/Install OS X El Capitan.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X El Capitan.app
   • Yosemite: sudo /Applications/Install OS X Yosemite.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X Yosemite.app
   • Mavericks: sudo /Applications/Install OS X Mavericks.app/Contents/Resources/createinstallmedia –volume /Volumes/MyVolume –applicationpath /Applications/Install OS X Mavericks.app
6. Type in your admin password. Next, type in Y and hit Return .

This will erase your hard drive first, and then convert your USB into a bootable installer. Wait for the process to finish, and then use your new bootable installer to reinstall your macOS using the steps below:

1. Shut down your Mac while your USB installer is connected.
2. Hold down the Option/Alt keys, then press the Power key.
3. You'll see your startup device list with the USB drive highlighted in yellow.
4. Choose your bootable drive and hit Return.
5. Choose Disk Utility and select your main hard drive.
6. Click Erase, then give your drive a name.
7. Select Mac OS Extended (Journaled) under Format and GUID Partition Map under Scheme.
8. Click Erase > Done.
9. Go to Disk Utility > Quit Disk Utility.
10. Hit the Install macOS button, then click Continue.
11. Follow the installation instructions.

The whole installation process can take around 30 minutes to one hour , so make sure that you have enough battery or your Mac is plugged in to avoid interruptions.

Summary

You can use any of the above methods to reinstall your macOS even without a Recovery partition. Vpn access macbook. However, if your computer is running Snow Leopard or older, you need to install the operating system using the original discs that shipped with your Mac (if you still have them), or purchase them from Apple for $19.99.