I can access network, but not internet.

From the menu bar, please select

 ▹ System Preferences... ▹ Network ▹ Advanced ▹ TCP/IP

What values are shown for the following?

Configure IPv4

IPv4 Address

Subnet Mask

Router

Please read this whole message before doing anything.

This procedure is a diagnostic test. It’s unlikely to solve your problem. Don’t be disappointed when you find that nothing has changed after you complete it.

The purpose of the test is to determine whether the problem is caused by third-party software that loads automatically at startup or login, by a peripheral device, by a font conflict, or by corruption of the file system or of certain system caches.

Disconnect all wired peripherals except those needed for the test, and remove all aftermarket expansion cards, if applicable. Start up in safe mode and log in to the account with the problem.

Note: If FileVault is enabled in OS X 10.9 or earlier, or if a firmware password is set, or if the startup volume is a software RAID, you can’t do this. Ask for further instructions.

Safe mode is much slower to start up and run than normal, with limited graphics performance, and some things won’t work at all, including sound output and Wi-Fi on certain models. The next normal startup may also be somewhat slow.

The login screen appears even if you usually login automatically. You must know your login password in order to log in. If you’ve forgotten the password, you will need to reset it before you begin.

Test while in safe mode. Same problem?

After testing, restart as usual (not in safe mode) and verify that you still have the problem. Post the results of the test.

Make sure that you have only one network adapter connected... WiFi OR wired, not both.

1. This procedure is a diagnostic test. It changes nothing, for better or worse, and therefore will not, in itself, solve the problem. But with the aid of the test results, the solution may take a few minutes, instead of hours or days.

The test works on OS X 10.8 ("Mountain Lion") and later. I don't recommend running it on older versions of OS X. It will do no harm, but it won't do much good either.

Don't be put off by the complexity of these instructions. The process is much less complicated than the description. You do harder tasks with the computer all the time.

2. If you don't already have a current backup, please back up all data before doing anything else. The backup is necessary on general principle, not because of anything in the test procedure. Backup is always a must, and when you're having any kind of trouble with the computer, you may be at higher than usual risk of losing data, whether you follow these instructions or not.

There are ways to back up a computer that isn't fully functional. Ask if you need guidance.

3. Below are instructions to run a UNIX shell script, a type of program. As I wrote above, it changes nothing. It doesn't send or receive any data on the network. All it does is to generate a human-readable report on the state of the computer. That report goes nowhere unless you choose to share it. If you prefer, you can act on it yourself without disclosing the contents to me or anyone else.

You should be wondering whether you can believe me, and whether it's safe to run a program at the behest of a stranger. In general, no, it's not safe and I don't encourage it.

In this case, however, there are ways for you to decide whether the program is safe without having to trust me. First, you can read it. Unlike an application that you download and click to run, it's transparent, so anyone who understands the code can verify what it does.

You may not be able to understand the script yourself. But variations of it have been posted on this website many times over a period of years. Any one of the millions of registered users could have read the script and raised the alarm if it was harmful. Then I would not be here now and you would not be reading this message. See, for example, this discussion.

Nevertheless, if you can't satisfy yourself that these instructions are safe, don't follow them. Ask for other options.

4. Here's a general summary of what you need to do, if you choose to proceed:

☞ Copy the text of a particular web page (not this one) to the Clipboard.

☞ Paste into the window of another application.

☞ Wait for the test to run. It usually takes a few minutes.

☞ Paste the results, which will have been copied automatically, back into a reply on this page.

These are not specific instructions; just an overview. The details are in parts 7 and 8 of this comment. The sequence is: copy, paste, wait, paste again. You don't need to copy a second time.

5. Try to test under conditions that reproduce the problem, as far as possible. For example, if the computer is intermittently slow, run the test during a slowdown.

You may have started up in safe mode. If the system is now in safe mode and works well enough in normal mode to run the test, restart as usual before running it. If you can only test in safe mode, do that.

6. If you have more than one user, and only one user is affected by the problem,, and the affected user is not an administrator, then please run the test twice: once while logged in as the affected user, and once as an administrator. The results may be different. The user that is created automatically on a new computer when you start it for the first time is an administrator. If you can't log in as an administrator, test as the affected user. Most personal Macs have only one user, and in that case this section doesn’t apply. Don't log in as root.

7. Load this linked web page (on the website "Pastebin.") Press the key combination command-A to select all the text, then copy it to the Clipboard by pressing command-C.

8. Launch the built-in Terminal application in any one of the following ways:

☞ Enter the first few letters of its name ("Terminal") into a Spotlight search. Select it in the results (it should be at the top.)

☞ In the Finder, select Go ▹ Utilities from the menu bar, or press the key combination shift-command-U. The application is in the folder that opens.

☞ Open LaunchPad and start typing the name.

Click anywhere in the Terminal window to activate it. Paste from the Clipboard into the window by pressing command-V, then press return. The text you pasted should vanish immediately.

9. If you're logged in as an administrator, you'll be prompted for your login password. Nothing will be displayed when you type it. You will not see the usual dots in place of typed characters. Make sure caps lock is off. Type carefully and then press return. You may get a one-time warning to be careful. If you make three failed attempts to enter the password, the test will run anyway, but it will produce less information. If you don't know the password, or if you prefer not to enter it, just press return three times at the password prompt. Again, the script will still run.

If the test is taking much longer than usual to run because the computer is very slow, you might be prompted for your password a second time. The authorization that you grant by entering it expires automatically after five minutes.

If you're not logged in as an administrator, you won't be prompted for a password. The test will still run. It just won't do anything that requires administrator privileges.

10. The test may take a few minutes to run, depending on how many files you have and the speed of the computer. A computer that's abnormally slow may take longer to run the test. While it's running, a series of lines will appear in the Terminal window like this:

Test started

Part 1 of 4 done at: … sec
…
Part 4 of 4 done at: … sec

The test results are on the Clipboard.

Please close this window.

The intervals between parts won't be exactly equal, but they give a rough indication of progress.

Wait for the final message "Please close this window" to appear—again, usually within a few minutes. If you don't see that message within about 30 minutes, the test probably won't complete in a reasonable time. In that case, press the key combination control-C or command-period to stop it. Then go to the next step. You'll have incomplete results, but still something.

In order to get results, the test must either be allowed to complete or else manually stopped as above. If you close the Terminal window while the test is still running, the partial results won't be saved.

11. When the test is complete, or if you stopped it manually, quit Terminal. The results will have been saved to the Clipboard automatically. They are not shown in the Terminal window. Please don't copy anything from there. All you have to do is start a reply to this comment and then paste by pressing command-V again.

At the top of the results, there will be a line that begins with the words "Start time." If you don't see that, but instead see a mass of gibberish, you didn't wait for the "close this window" message. Please wait for it and try again.

If any private information, such as your name or email address, appears in the results, anonymize it before posting. Usually that won't be necessary.

12. When you post the results, you might see an error message on the web page: "You have included content in your post that is not permitted," or "The message contains invalid characters." That's a bug in the software that runs this website. Please post the test results on Pastebin, then post a link here to the page you created.

If you have an account on Pastebin, please don't select Private from the Paste Exposure menu on the page, because then no one but you will be able to see it.

13. When you're done with the test, it's gone. There is nothing to uninstall or clean up.

14. This is a public forum, and others may give you advice based on the results of the test. They speak for themselves, not for me. The test itself is harmless, but whatever else you do may not be. For others who choose to run it, I don't recommend that you post the test results on this website unless I asked you to.

15. The linked UNIX shell script bears a notice of copyright. Readers of ASC may copy it for their own personal use. Neither the whole nor any part may be redistributed.

TeamViewer, Evernote, Parallels, LogMeIn... Do you actually use all of this stuff? TeamViewer and LogMeIn are two things I will never have on any of my systems because of the risk of being hacked.

A

The backup drive is malfunctioning and must be replaced immediately, before you do anything else.

B

You're on an unsecured Wi-Fi network. If it's your network, that's very dangerous. Change your router's settings so that it uses WPA 2 Personal encryption. If it doesn't support that standard, it should be replaced. I can't give you specific instructions for changing the setting, because all routers are different. Refer to the manufacturer's documentation.

C

If your router is also your broadband device, and if it's operating in bridge mode, then only one device on the network will be able to connect to the Internet at a time. A virtual machine counts as a device.

D

Some OS X files (Installer package receipts) are missing or invalid. Other OS files may also be missing or invalid.

If you don't already have a current backup, please back up all data, then reinstall the OS.* You don't need to erase the startup volume, and you won't need the backup unless something goes wrong. If the system was upgraded from an older version of OS X, you may need the Apple ID and password you used.

There are ways to back up a computer that isn't fully functional. Ask if you need guidance.

If you installed the Java runtime distributed by Apple and still need it, you'll have to reinstall it. The same goes for Xcode. All other data will be preserved.

*The linked support article refers to OS X 10.11 ("El Capitan"), but the procedure is the same for OS X 10.7 ("Lion") and later.

E

Some of your user files (not system files) have incorrect permissions or are locked. This procedure will unlock those files and reset their ownership, permissions, and access controls to the default. If you've intentionally set special values for those attributes, they will be reverted. In that case, either stop here, or be prepared to recreate the settings if necessary. Do so only after verifying that those settings didn't cause the problem. If none of this is meaningful to you, you don't need to worry about it, but you do need to follow the instructions below.

Please back up all data before proceeding.

Step 1

If you have more than one user, and the one in question is not an administrator, then go to Step 2.

Enter the following command in the Terminal window in the same way as before (triple-click, copy, and paste):

sudo find ~ $TMPDIR.. -exec chflags -h nosappnd,noschg,nosunlnk,nouappnd,nouchg {} + -exec chown -h $UID {} + -exec chmod +rw {} + -exec chmod -h -N {} + -type d -exec chmod -h +x {} + 2>&-

You'll be prompted for your login password, which won't be displayed when you type it. Type carefully and then press return. You may get a one-time warning to be careful. If you don’t have a login password, you’ll need to set one before you can run the command. If you see a message that your username "is not in the sudoers file," then you're not logged in as an administrator.

The command may take several minutes to run, depending on how many files you have. Wait for a new line ending in a dollar sign ($) to appear, then quit Terminal.

Step 2 (optional)

Take this step only if you have trouble with Step 1, if you prefer not to take it, or if it doesn't solve the problem.

Start up in Recovery mode. You may be prompted to select a language, then the OS X Utilities screen will appear.

If you use FileVault 2, select Disk Utility, then select the icon of the FileVault startup volume ("Macintosh HD," unless you gave it a different name.) It will be nested below another drive icon. Click the Unlock button in the toolbar and enter your login password when prompted. Then quit Disk Utility to be returned to the main screen.

Select

Utilities ▹ Terminal

from the menu bar. A Terminal window will open. In that window, type this:

resetp

Press the tab key. The partial command you typed will automatically be completed to this:

resetpassword

Press return. A Reset Password window will open. You’re not going to reset a password.

Select your startup volume ("Macintosh HD," unless you gave it a different name) if not already selected.

Select your username from the menu labeled Select the user account if not already selected.

Under Reset Home Directory Permissions and ACLs, click the Reset button.

Select

 ▹ Restart

from the menu bar.

F

Back up all data.

Run the following command in the same way as before. It moves to the Trash "semaphore" files that have not been cleaned up by the system and may be interfering with normal operation. The files are empty; they contain no data. There will be no output this time.

find L*/{Con*/*/Data/L*/,}Pref* -type f -size 0c -name *.plist.??????? -exec mv {} .Trash/ \; 2>&-

Log out or restart the computer and empty the Trash.

G

I suggest that you remove "Cocktail," which, like all other so-called "utilities," is at best useless.

Any third-party software that doesn't install from the App Store or by drag-and-drop into the Applications folder, and uninstall by drag-and-drop to the Trash, is a system modification.

Whenever you remove system modifications, they must be removed completely, and the only way to do that is to use the uninstallation tool, if any, provided by the developers, or to follow their instructions. If the software has been incompletely removed, you may have to re-download or even reinstall it in order to finish the job.

I never install system modifications myself, and except as stated in this comment, I don't know how to uninstall them. You'll have to do your own research to find that information.

Here are some general guidelines to get you started. Suppose you want to remove something called “BrickMyMac” (a hypothetical example.) First, consult the product's Help menu, if there is one, for instructions. Finding none there, look on the developer's website, say www.brickmymac.com. (That may not be the actual name of the site; if necessary, search the Web for the product name.) If you don’t find anything on the website or in your search, contact the developer. While you're waiting for a response, download BrickMyMac.dmg and open it. There may be an application in there such as “Uninstall BrickMyMac.” If not, open “BrickMyMac.pkg” and look for an Uninstall button. The uninstaller might also be accessed by clicking the Customize button, if there is one.

Back up all data before making any changes.

You will generally have to restart the computer in order to complete an uninstallation. Until you do that, there may be no effect, or unpredictable effects.

If you can’t remove software in any other way, you’ll have to erase and install OS X. Never install any third-party software unless you're sure you know how to uninstall it; otherwise you may create problems that are very hard to solve.

Trying to remove complex system modifications by hunting for files by name often will not work and may make the problem worse. The same goes for "utilities" such as "AppCleaner" and the like that purport to remove software.