Apple was the first computer company to facilitate network file sharing. Decades after this feature was introduced on the Mac, it’s less important in the age of cloud storage. Unless you’re on a corporate network, and often even so, it’s easiest to transfer files to a central repository by copying them to a folder or volume on your desktop that syncs. Cloud storage also bypasses network configuration issues, such as the dreaded “double NAT,” which can prevent Internet file exchange connections from being established.
However, it’s often useful to allow files stored on your Mac to be accessed by other computers on a local network. Let’s look at what is needed to set it up.
Enable file sharing
start with System Preferences > Share. This one stop shop for all network services macOS includes a checkbox for file sharing. Enabling File Sharing allows you or anyone with an account on this Mac to access the computer’s file server using account credentials and without requiring additional configuration. Anyone with an account with Admin under their account name in Users and Groups can access files on startup and all mounted volumes. People with regular user accounts can access their home directory and the Shared folder in the Home folder by default.
Apple has abandoned its original file sharing software, AFP (Apple Filing Protocol), in favor of SMB (Server Message Block) launched by Microsoft. This allows a wide range of devices to connect to a Mac that has file sharing enabled. You can view Apple’s support history by selecting File Sharing in the sharing preferences pane and clicking Options. For the latest versions of macOS, only the “Share files and folders using SMB” checkbox appears, an odd choice. But for several years, AFP and SMB were selectable separately before AFP disappeared.
However, this is also where you can enable backward compatibility for Windows systems that use an older version of SMB.
Configure file sharing
You have several options for what you might share and with whom:
Limit sharing to you and others with regular and administrator accounts on the Mac. This is the default and requires no additional work.
Create shared folders that people with regular Mac accounts can access to create pooled local storage or a write-only dropbox. (That’s the tiny “drop box”: a place to drop things off.)
Create sharing-only users, who cannot connect to a Mac or connect to it through a Terminal session; they can only access shared folders. (See “How to create a share-only user in macOS to limit access.”)
Add shared folders by clicking the + (plus) at the bottom of the shared folders list. You can select any volume or folder. Delete a folder or volume by selecting it and clicking – (minus).
Assign users and permissions to shared folders by selecting the folder in the Shared Folders list, then editing existing permissions in the Users list. You can add user groups by clicking +. (You can also remove certain users and groups by selecting one and clicking “-“.)
The permissions next to each user or group entry are the same as those found in the Finder:
Read and write: all access, including deleting and adding items.
Read-only: Get everything in the folder, including nested items.
Write Only (Dropbox): Allows a user to copy a file to the destination but not view it or any other contents of the folder.
No Access: Available only to Everyone to disable access to all other users and guest logins.
If the guest user in System Preferences > Users & Groups has checked “Allow guest users to connect to shared folders”, guest users can access any shared folder that has Everyone set to a value other than No access. However, you can also explicitly disable guest access by Ctrl-clicking a shared folder, choosing Advanced Options, and unchecking “Allow guest users”.
You can also use advanced options to enable networked Time Machine backups to a particular folder on a volume. I explain this process in “How to set your Mac as a shared backup destination for Time Machine”.
A quick warning! With file sharing active, it’s conceivable that anyone, anywhere in the world can access your Mac and act as a guest user or try to log in. On most home networks, the configuration of the ISP and router makes this nearly or completely impossible. Still, I suggest disabling or restricting guest access to avoid sharing anything you didn’t intend to share with the world.
Connect to a Mac’s file server
From macOS, you can connect to a file server in Finder. Open any Finder and look under the list of locations. Macs with file sharing or screen sharing enabled appear there. (If you don’t see them, go to Finder > Preferences > Sidebar and check Bonjour computers.) Click on any server, then click Connect as, enter credentials and select an available volume.
Some servers will not appear in the Finder, depending on your local network. Click it Network link in the Finder sidebar under Locations or choose Go > Network (Command-Shift-K).
If you need to enter the address of a Mac, choose Go > Connect to Server (Command-K). You enter the address in the format smb://addressas smb://10.0.1.120, then click Connect or press Return. A Finder window appears, as if you had clicked on a server in the Finder sidebar.
For Macs that you cannot see via Bonjour or to connect to a Mac from a Windows computer or other system, you can find the Mac’s address in System Preferences > Network. Select any active interface from the list on the left, and in the main section of the pane under Connected, the IP address will appear.
Ask for Mac 911
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