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      How to Fix the Error Establishing a Database Connection in WordPress


      Few things are as frustrating as finding that your website is down — particularly if you rely on it for business. The Error Establishing a Database Connection message represents a serious issue and prevents all access to your site, so fixing it is a top priority. However, if you’re not familiar with how WordPress works, it can be a confusing problem.

      Don’t fret. Although this error is serious, it’s also highly fixable. With a few troubleshooting steps, you can have your site back online in no time. Here’s what we’ll cover:

      Let’s get started!

      Got a WordPress Error? No Problem

      You can skip troubleshooting if you sign up for DreamPress hosting. Our friendly WordPress experts are always standing by to solve your website problems — big or small.

      Understanding the Error Establishing a Database Connection in WordPress

      Before we dig too much into this particular error message, let’s have a brief lesson on how WordPress sites work. Nearly all website information — including post data, plugin settings, login credentials, and more — is stored and organized in a MySQL database.

      When a visitor comes to your site, WordPress uses PHP to query the database and pull the correct information, which is then displayed as the complete page.

      If, for whatever reason, WordPress can’t access your site’s database or it isn’t working properly, the result is an Error Establishing a Database Connection message.

      The Error Establishing a Database Connection message on a WordPress site.

      This error prevents the entire page from loading. In fact, you won’t even be able to access the WordPress dashboard (your site’s back end).

      If your site uses caching, visitors may still see stored copies of your pages. Therefore, if you catch the error early and resolve the problem before your site’s cache refreshes, you can avoid too many interruptions to your site and business.

      Fortunately, as WordPress errors go, a database connection error is usually pretty simple to resolve. The most common cause, by far, is just a mismatch of login credentials for the database.

      Common Causes of the Error Establishing a Database Connection

      There are four typical causes of the database connection error:

      • Incorrect database login credentials. Possibly the most common cause of the Error Establishing a Database Connection is simply that WordPress has incorrect login credentials for your database. This could be either the database name, username, or password. Remember, these login details are different from the ones you use to access your site.
      • Database corruption. A WordPress MySQL database contains a lot of information. If any part is deleted or corrupted, the result can be the error in question. Corruption can result from manually tinkering with the database, but it can also just happen as a consequence of normal use. Although MySQL is quite robust, nothing is perfect, and errors do occur.
      • WordPress core file corruption. Similarly, corruption can occur in the core WordPress files that make up your site. Even though these files are outside the database, they may sometimes result in the same error.
      • Problems with the web server or hosting provider. If problems arise with your host or server (if you’re self-hosting) and WordPress can’t reach it to query the database, it will throw this error. These problems can include outages, data loss, and hardware failures.

      As we said, incorrect credentials are the most common cause of the error, but any of these could be the culprit. For that reason, fixing the error can involve some troubleshooting.

      How to Fix the Error Establishing a Database Connection in WordPress (In 4 Steps)

      Although this is a serious error, it’s fortunately fairly easy to resolve. Below, you’ll find step-by-step instructions for troubleshooting and fixing the problem. Note that you should try each step in order, only moving to the next if one doesn’t work.

      Step 1: Check Your WordPress Database Credentials

      Since this is the most likely cause of the error, it should also be the first step in your troubleshooting. The first thing you’ll need to do is locate the credentials WordPress is currently using to access your database.

      This information is stored in your site’s wp-config.php file. You can use a Secure File Transfer Protocol (SFTP) client to access it.

      Alternatively, if your site is hosted with DreamHost, you can access the file system from the DreamHost Control Panel. To do so, sign in to your control panel and navigate to Domains > Websites. Hover the mouse over the domain you’d like to fix, then click ‘manage’ to see the folder icon. Then click on the file folder symbol next to the site that’s experiencing the error.

      Inside the file browser, select the folder named after your website, then open wp-config.php. Here, look for three pieces of information — the database name, username, and password. They should be near the top of the file.

      The database login credentials in the wp-config.php file.

      With this information in hand, head to your DreamHost Panel and navigate to More > MySQL Databases. Look for the hostname that corresponds to your website’s name. It will be formatted as mysql.yoursitename.com, with “yoursitename” being the name of your website.

      If the hostname isn’t on this page, skip down to Step 2 and come back here when you’re done adding it.

      In the section called Database(s) on this server, make sure the database name matches the one you pulled from wp-config.php earlier. If it does, this isn’t the problem, and you can move on to the next step.

      If it doesn’t match, go back to wp-config.php and update it with the correct database name.

      Next, you can find the usernames that have access to each database beside their names on the MySQL Databases page.

      The usernames that have access to the database listed in the DreamHost Control Panel.

      To view the password, click on the username. On the page that opens, scroll down to the Current Password field and click on Show.

      The password options for a database user in the DreamHost Control Panel.

      If the username or password doesn’t match your wp-config.php file, update it with the correct details. Alternatively, if the username matches but the password doesn’t, you could update the database password on the User Details screen.

      Step 2: Check Your Database Host Information

      If you’ve checked the database login credentials and fixed any errors, but you’re still getting the Error Establishing a Database Connection message, the next thing you should check is your database host information.

      The hostname for your database can be found in wp-config.php, right alongside the database name and login credentials.

      The MySQL database hostname in the wp-config.php file.

      Note this information, then head back to your DreamHost Panel and navigate to More > MySQL Databases. This time, you’re looking to make sure the hostname in your wp-config.php file is listed on this page. If it’s not, you’ll need to add it.

      To add a hostname, simply click on the Add New Hostname button. On the next page, enter the hostname you want to use and select the correct website domain from the dropdown.

      When you’re finished, click on Create this MySQL hostname now! Note that it can take a few hours for this new hostname to propagate through the DNS, so feel free to take a break here. When some time has passed, come back and check if your site is working. If you’re still getting the database error message, proceed to the next step.

      Step 3: Repair Your WordPress Database

      If you’re still receiving the error message, you can try repairing the database to fix possible corruption. We recommend using the built-in WordPress database repair tool for this.

      To access it, open up your wp-config.php file and add the following code at the end:

      define('WP_ALLOW_REPAIR', true);

      Next, open a new browser tab and navigate to https://yoursitename.com/wp-admin/maint/repair.php, replacing “yoursitename” with your website’s actual domain. This will bring up the database repair tool.

      The WordPress database repair tool.

      Click on Repair Database and let it do its thing. You can choose Repair and Optimize Database if you like, but it takes considerably longer. Either way, when the tool is finished, load your website again and check for the error. If it’s gone, then you’ll know a corrupted database was the cause.

      However, if you’re still seeing the error message, head to the next step. Before you do, make sure to head back into wp-config.php and delete the code you added to turn on the tool. If you leave it there, someone with ill intentions could gain access to your site easily.

      Step 4: Check if Your Database Server Is Down

      If all the above steps have failed, one final possibility is that your database server has gone down. At this point, it’s a good idea to verify with your hosting provider that everything is working correctly.

      There are a number of reasons why your database host or server might be experiencing issues:

      • Too many simultaneous connections to the database. Some providers have limits on how many connections a server can have at one time.
      • Problems with another site on your shared hosting server. If you’re on a shared hosting plan, you’re splitting resources with other sites. If one of them has problems, it can spill over to your site. This is one of the reasons dedicated or managed WordPress hosting plans can be beneficial.
      • Hardware troubles. Hardware eventually fails, and it’s possible that the server your database is stored on has done just that. Ideally, your host will have redundancies in place so that if one server goes down, there’s another copy of your data available, but this isn’t always the case — especially if you’re hosting your own database on a home or office server.

      Your best bet here is to reach out to your web host and inquire about outages or other known issues. If there are none, you can report your problem and ask the support staff to look into it for you.

      At DreamHost, you can always find your support options by clicking on the Support button in the top right corner of your control panel:

      Support options in the DreamHost Control Panel.

      DreamHost offers 24/7 support, so you can get help any time you need it.

      Additional Tips and Solutions That Have Worked for Other Users

      If you’ve tried all of the above tips and you’re still having trouble with the Error Establishing a Database Connection, there are a couple of other options that have worked for some users. You can try these either before or after going through the troubleshooting steps above:

      • Update your WordPress site URL. If you’ve recently moved your WordPress installation for any reason (such as moving to a new domain name or migrating to HTTPS), you may need to update your site URL in the database. You can find full instructions for doing so in our knowledge base.
      • Reboot your web server. This one might seem a little basic, but sometimes the simplest solutions are the most effective. If you host your database on your own server, try turning it off and back on. Computers are complex, and a simple reboot can fix all manner of odd problems you may be experiencing.
      • Ask for help. If you’re not comfortable doing your own troubleshooting, or you’ve tried everything and still can’t get rid of the Error Establishing a Database Connection message, there’s no shame in reaching out for help. You can get in touch with DreamHost support 24/7 by clicking the Support button in your DreamHost panel. You can also try searching on help forums such as Stack Exchange or Quora. Your question may have already been answered on one of these sites. If not, you can always ask.

      At this point, you’ve hopefully resolved the issue and gotten your site back up and running.

      Take Your WordPress Website to the Next Level

      Whether you need help navigating the WordPress dashboard, fixing incorrect database credentials, or finding the plugins folder, we can help! Subscribe to our monthly digest so you never miss an article.

      Further Reading

      Want to learn more about fixing common WordPress errors? We’ve got you covered!

      Ready to Fix a Database Connection Issue?

      If you’ve gone to check on your website and found yourself greeted by the Error Establishing a Database Connection message, you’re not alone. It’s a common error with relatively simple fixes, so getting your site up and running again shouldn’t be too difficult.

      You should follow these steps to troubleshoot a database connection error:

      1. Check your WordPress database credentials.
      2. Check your database host information.
      3. Repair your WordPress database.
      4. Check if your database server is down.

      If you’d rather not have to deal with these types of problems in the future, consider upgrading to DreamPress, our managed WordPress hosting service. Then you can leave the troubleshooting to us!



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      How to Fix the 500 Internal Server Error in WordPress (10 Tips)


      Seeing a 500 internal server error where your website should be is enough to throw anyone into a panic. When your website goes down, you lose out on potential traffic and sales. If it’s offline for a while, it can also negatively impact your Search Engine Optimization (SEO) efforts.

      Fortunately, there are plenty of ways to go about fixing this error. Many of these solutions are fairly straightforward, and you don’t need a lot of technical know-how to start troubleshooting.

      In this guide, we’ll cover what the 500 internal server error in WordPress is and discuss some potential causes. Then we’ll give you 10 tips to help you get your website back in working order.

      1. Back up your website.
      2. Try reloading the page.
      3. Clear your browser cache.
      4. Access your error logs.
      5. Check for the “Error Establishing a Database Connection.”
      6. Look for permission errors.
      7. Increase your PHP memory limit.
      8. Check for problems with your .htaccess file.
      9. Look for coding or syntax errors in your CGI/Perl script.
      10. Ask your web host about potential server issues.

      Let’s get started!

      Dealing with the WordPress Internal Server Error?

      Avoid troubleshooting when you sign up for DreamPress. Our friendly WordPress experts are available 24/7 to help solve website problems — big or small.

      What Is the 500 Internal Server Error?

      The 500 internal server error is frustratingly nonspecific. When the error occurs, you usually don’t get many details about it. In fact, you might not receive any information at all.

      An example of a 500 internal server error screen.

      The 500 error is a generic issue that isn’t specific to WordPress. Chances are you’ve seen it before during your internet explorations. Despite the name, it doesn’t necessarily mean that something is wrong with your server. It could be an issue with your website or browser.

      If you do see this error on your site, you’ll want to get it fixed as quickly as possible. A 500 error can impact your SEO if allowed to linger. If your site is crawled while it’s offline, there’s a chance that Google may interpret the error as an issue with your website.

      This error can also hurt your User Experience (UX) and give visitors the impression that you’re unprofessional. Not only can a poor UX affect the way Google ranks your site, but it can cause you to lose customers as well. After all, you can’t do business if your site isn’t accessible.

      A wide variety of situations can result in the 500 error, making it a bit of a chore to sort out. Potential causes of the 500 internal server error in WordPress include:

      • Plugin compatibility issues
      • Exhausted PHP memory limit
      • Corrupted files
      • Coding or syntax errors

      The fact that the error message itself tends to be vague doesn’t help. Fortunately, you can solve many of these issues on your own with a bit of know-how.

      Variations on the 500 Internal Server Error

      Depending on your operating system, browser, and the cause of the error, there are variations in how it will appear. For example, if a database connection can’t be established, you might see something like this:

      An error establishing a database connection message.

      A plain white screen, sometimes referred to as the White Screen of Death (WSoD), can indicate a 500 internal server error.

      A blank browser window due to a 500 error.

      Also, many site owners have the option to customize their 500 error messages. So you might see this error in many different forms.

      How to Fix the 500 Internal Server Error in WordPress (10 Tips)

      Now that you’ve had an introduction to the 500 internal server error, it’s time to discuss how to resolve it. Let’s take a look at ten tips you can use to fix this issue in WordPress.

      1. Back up your website.

      Before tinkering under the hood, it’s always smart to make a backup of your website. If DreamHost hosts your site, you can take advantage of our one-click backup feature. You can also create a manual backup if you prefer.

      To make a complete backup, you’ll need to save copies of your WordPress files as well as your databases. You can back up your site’s files using a Secure File Transfer Protocol (SFTP) client such as FileZilla.

      Once you’re connected to your server, navigate to the WordPress files you want to save. These files include the WordPress core installation, plugins, themes, images, and more. To save the files, simply right-click on them and select Download.

      How to download WordPress files via SFTP.

      Now you’ll need to back up your database, which you can do by logging into phpMyAdmin. Select the database you want to download from the left-hand panel, and then click on the Export tab.

      You’ll then need to choose between a “Quick” or a “Custom” export. The Quick export will likely work just fine unless you need to manage more advanced options.

      Options for downloading a WordPress database using phpMyAdmin.

      Click on the Go button, and your download should start. Once your website is safely backed up, you can get to work on fixing that 500 error.

      2. Try reloading the page.

      Let’s start with the best-case scenario. Some situations that cause a 500 internal error clear up on their own within a few minutes. For example, if you’ve just made changes to a plugin or theme, or if your host is experiencing unusually heavy traffic, you may see a server error. If this is true in your case, you’re in luck, as a simple page reload should get things back to normal.

      Therefore, the first thing to try is simply waiting a minute or two, during which the error will hopefully resolve itself. Then you can try reloading the page by pressing F5 or (command + R if you’re using a Mac).

      3. Clear your browser cache.

      Another potential server error fix that’s quick and easy is clearing your browser cache. It’s possible the cache became corrupted, which would cause problems when attempting to access websites.

      First, you might check Down For Everyone Or Just Me. This will determine whether there’s a widespread problem or you’re the only one experiencing difficulties.

      Amazon.com’s status on Down for Everyone or Just Me.

      If you’re alone in your 500 error frustration, the problem may be your browser. Try accessing your site from a different browser. If an alternative works, it’s a sign that the issue is with your cache.

      In Google Chrome, you can clear your cache by pressing Ctrl + Shift + Delete. Alternatively, you can click on the three vertical dots in the top-right corner, followed by More tools > Clear browsing data.

      Options for clearing the browser cache in Chrome.

      Be sure to check the Cached images and files box. Then click on the Clear data button.

      In Firefox, you can clear the cache using the Ctrl + Shift + Delete keyboard shortcut. This will open the Clear Recent History window. In the Time range to clear drop-down menu, select Everything. Check the Cache box, and then click on OK.

      Options for clearing browser data in Firefox.

      In Safari, you can navigate to the History menu item and choose Clear History. Keep in mind that this will delete everything, including cookies and visited pages.

      How to clear the browser cache in Safari.

      Once you’ve cleared your browser cache, you can attempt to access your website again. If you’re still seeing the 500 internal server error, it’s time to move on to more involved fixes.

      4. Access your error logs.

      Your site’s error logs may provide insight into what’s causing the 500 error. Depending on your host, these logs may be cycled quite often, so you’ll want to take a look as soon as possible.

      You can check your error logs by accessing your site’s files via SFTP and looking for the /logs directory. Next, select the site that’s experiencing the error. You may see several directories at this point. You’ll want to check the one with the most recent date.

      Error and access log files accessed via FileZilla.

      You can view the log by downloading it and opening it with your preferred text editor. Hopefully, your error logs will provide you with some additional context for the 500 error.

      Another option is to enable the WordPress debug log. You can do this by connecting to your site via SFTP and opening your wp-config.php file. Within it, look for the following line:

      define('WP_DEBUG', false);

      Once you find it, replace it with the following:

      define( 'WP_DEBUG', true );
      
      define( 'WP_DEBUG_DISPLAY', false );
      
      define( 'WP_DEBUG_LOG', true );

      This will create a debug.log file, which you can find under the /wp-content/ directory. Just be sure to change the WP_DEBUG value back to “false” when you’re done troubleshooting.

      5. Check for the ‘Error Establishing a Database Connection.’

      If there’s been a problem establishing a database connection, not only will your site be offline for visitors, but you won’t be able to access the WordPress admin dashboard either. There are a few possible causes of this:

      • Incorrect database login credentials
      • A corrupted WordPress database
      • A corrupted WordPress installation file

      Let’s start with incorrect login credentials, as this is a common cause of the database connection error. If you’re a DreamHost user, you can find your database credentials in your panel. However, if you use a different host, you’ll likely follow a similar procedure.

      Navigate to MySQL Databases and find the one that corresponds to your website under the Database(s) on this server section. Here, you’ll find your database name under the Database heading. The username is listed under the Users Access column.

      Alt-text: Where to find your MySQL username in DreamPanel.

      To find the password, click on the username. On the next screen, scroll down and click on the Show button next to the password field.

      How to find your database password in DreamPanel.

      Next, you’ll compare these credentials to those in your wp-config.php file. You can access this file in your site’s main directory via SFTP. Once you have the file downloaded, open it and verify that the information under MySQL Settings matches what you found in your panel.

      Checking MySQL settings in the wpconfig.php file.

      Next, if your database is corrupted, you can quickly repair it through phpMyAdmin. Log in and click on your database in the left panel. Select all of the tables in the database, and then choose the Repair table option from the drop-down menu.

      Repairing a database in phpMyAdmin.

      Finally, let’s look at how to handle a corrupted WordPress installation file. Start by downloading a new copy of WordPress and unzipping the file. You’ll need to delete the wp-content folder and the wp-config-sample.php file.

      Deleting files from a new WordPress installation.

      Upload the rest of the files to your site via SFTP, overwriting any existing ones. You now have a brand new, uncorrupted WordPress installation. You’ll also want to clear your browser cache before checking your website again.

      6. Look for permission errors.

      If any of your files have permissions set incorrectly, you may see the 500 internal server error as a result. Again, you can check and change these permissions using SFTP.

      Right-click on any file and select File permissions to open a new dialogue window. In this window, you can check and, if necessary, set new permissions for the file.

      Checking and updating file permissions using FileZilla.

      Typically, you’ll want to set files to “644” and directories and executables to “755”. However, you may want to check with your host if you’re unsure about the correct values.

      7. Increase your PHP memory limit.

      Another reason you might see the 500 internal server error is if you’ve exceeded your server’s PHP memory limit. There are several ways to increase your limit, and they all involve using SFTP.

      Before you try increasing your memory limit, you may want to start by seeing what it’s currently set to. You can do this through the WordPress admin dashboard. Keep in mind that, with some variations of the 500 error, you won’t be able to access the dashboard. If that’s the case, you may have to skip this step.

      From your WordPress dashboard, navigate to Tools > Site Health. Click on Info at the top of the screen, and scroll down to the Server section. You should see your PHP memory limit there.

      How to check your WordPress site’s PHP memory limit.

      To increase the PHP memory limit, there are a few files you can edit. One is your .htaccess file, typically located in your site’s root directory. Open the file and add the following code:

      php_value memory_limit xxxM

      You can replace the “xxx” with your desired amount of memory. Usually, 256M is plenty.

      You can also increase your memory limit by editing your php.ini file. You should be able to find this file in your root directory. If not, you can go ahead and create one. Add or update its code to the following:

      memory_limit = xxxM

      Another option is to add in the following code at the top of your wp-config.php file:

      define('WP_MEMORY_LIMIT', 'xxxM');

      If this resolves the 500 error, your next task will be to figure out what is causing the memory limit exhaustion. It could be a problematic plugin or theme. You might consider reaching out to your host for help on finding the exact server diagnostics.

      8. Check for problems with your .htaccess file.

      Your .htaccess file is one of the core WordPress files. It contains rules for your server, so it could contribute to a 500 internal server error.

      If your .htaccess file has become corrupted, you’ll want to go ahead and create a fresh one. Start by logging into your site via SFTP and finding your .htaccess file. Rename the file to .htaccess_old.

      Renaming a file in FileZilla.

      Now, create a new .htaccess file in your text editor and paste in the following:

      # BEGIN WordPress
      
      RewriteEngine On
      
      RewriteRule .* - [E=HTTP_AUTHORIZATION:%{HTTP:Authorization}]
      
      RewriteBase /
      
      RewriteRule ^index.php$ - [L]
      
      RewriteCond %{REQUEST_FILENAME} !-f
      
      RewriteCond %{REQUEST_FILENAME} !-d
      
      RewriteRule . /index.php [L]
      
      # END WordPress

      Go ahead and upload your newly created .htaccess file. Then refresh your site in your browser, and check to see whether the error message is showing.

      9. Look for coding or syntax errors in your CGI/Perl script.

      If you’re running Common Gateway Interface (CGI) scripts, any coding errors you’ve made could result in a 500 error. To unearth potential issues with your CGI scripts, log into your site using Secure Shell Access (SSH).

      Once you’ve logged in, you can troubleshoot your CGI with this command:

      [server]$ ./cgi_name.cgi

      The terminal should return a general error message and the line number the culprit is located on. From there, you can work your coding magic!

      When working with CGI, there are a few best practices to keep in mind to avoid problems. First, it’s wise to use a plain text editor to ensure that you maintain ASCII format. When you upload scripts, you should also be able to select ASCII mode in your FTP client.

      Changing the transfer type option in FileZilla.

      Finally, if necessary, upload to the cgi-bin directory on your server. Then you can double-check your files’ permissions once you have them uploaded.

      10. Ask your web host about potential server issues.

      If all else fails, there may be a server issue, which only your host can confirm. Unfortunately, if your host’s server is experiencing a problem, you may have to wait out some website downtime.

      If you’re a DreamHost client, you can check the DreamHost Status page. This resource provides you with information on all of our services.

      The DreamHost status page.

      If you run into any problems while trying to repair the 500 internal server error, you can always reach out to our tech support team. They’re ready and waiting to lend you a hand! If you’ve followed the tips in this guide, you’ll have plenty of valuable information for the technician.

      Ready to Dive into Your Error Log?

      Whether you need help with file permission, identifying a hidden file, or dealing with a faulty plugin, we can help! Subscribe to our monthly digest so you never miss an article.

      Let’s Get Your WordPress Website Back on Track

      While having to sort out a 500 internal server error isn’t exactly fun, it’s also not as painful as you might imagine. With a little patience and the tips we’ve provided, you should be able to make some progress on getting your website back online.

      You can start small by refreshing your page and clearing your browser cache. Then you might want to move onto more involved fixes, such as increasing your PHP memory limit. If you’re not able to resolve the error on your own, DreamHost’s award-winning tech support is just a click away.

      When you do run into errors, it’s easier to get back up and running when you have a reliable hosting provider. DreamPress is fast, secure WordPress hosting with powerful features to help make your site a success!



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      HAProxy Network Error: cannot bind socket



      Part of the Series:
      Common HAProxy Errors

      This tutorial series explains how to troubleshoot and fix some of the most common errors that you may encounter when using the HAProxy TCP and HTTP proxy server.

      Each tutorial in this series includes descriptions of common HAProxy configuration, network, filesystem, or permission errors. The series begins with an overview of the commands and log files that you can use to troubleshoot HAProxy. Subsequent tutorials examine specific errors in detail.

      Introduction

      An HAProxy cannot bind socket error message is generated when there is another process listening on the same interface and TCP port combination that HAProxy is configured to use, or when HAProxy attempts to use an IP address that is not assigned to a network interface. Both error conditions derive from the underlying operating system’s network stack.

      In the first case, when there is another process that is already using an interface and port that HAProxy is attempting to bind to, the underlying error on Linux is EADDRINUSE. The issue is that only a single process can be bound to an IP address and port combination at any given time.

      In the second case, when HAProxy is attempting to use an IP address that is not assigned to an interface on the system, the underlying error on Linux is EADDRNOTAVAIL. The issue here is that an IP socket cannot be created using an address that is not available to the operating system.

      However, both underlying errors generate the same HAProxy error message, so troubleshooting a cannot bind socket error requires examining the list of currently used sockets and IP addresses on a Linx system.

      To detect a cannot bind socket error message, you will need to examine systemctl and journalctl output to determine the IP address and port combination that are causing the error. Then you can inspect other running processes and network interfaces and decide how to resolve the issue, whether it is by switching servers, changing the IP address or port that HAProxy uses, or any combination of these options.

      Troubleshooting with systemctl

      Following the troubleshooting steps from the How to Troubleshoot Common HAProxy Errors tutorial at the beginning of this series, the first step when you are troubleshooting an cannot bind socket error message is to check HAProxy’s status with systemctl.

      The output from systemctl status will in many cases contain all the diagnostic information that you need to resolve the error. It may include the IP address that HAProxy is using, as well as the port that it is attempting to bind to. The output will also indicate how long HAProxy has been unable to start so that you can determine how long the issue has been affecting HAProxy.

      Note: If you are using Ubuntu or a Debian-derived Linux distribution, systemctl does not include output from HAProxy with a cannot bind socket error message that describes the problem. Skip to the the next section of this tutorial, Troubleshooting Using journalctl Logs to learn how to examine the systemd logs to find the conflicting IP address or port.

      On CentOS, Fedora and RedHat-derived systems, use this systemctl command to examine HAProxy’s status:

      CentOS and Fedora Systems

      • sudo systemctl status haproxy.service -l --no-pager

      The -l flag will ensure that systemctl outputs the entire contents of a line, instead of substituting in ellipses () for long lines. The --no-pager flag will output the entire log to your screen without invoking a tool like less that only shows a screen of content at a time.

      Since you are troubleshooting a cannot bind socket error message, you should receive output that is similar to the following:

      Output

      ● haproxy.service - HAProxy Load Balancer Loaded: loaded (/usr/lib/systemd/system/haproxy.service; disabled; vendor preset: disabled) Active: failed (Result: exit-code) since Wed 2020-08-19 14:57:05 UTC; 3s ago Process: 138738 ExecStart=/usr/sbin/haproxy -Ws -f $CONFIG -p $PIDFILE (code=exited, status=1/FAILURE) Process: 138736 ExecStartPre=/usr/sbin/haproxy -f $CONFIG -c -q (code=exited, status=0/SUCCESS) Main PID: 138738 (code=exited, status=1/FAILURE) Aug 19 14:57:05 92214d8ff5e2 systemd[1]: Starting HAProxy Load Balancer... Aug 19 14:57:05 92214d8ff5e2 haproxy[138738]: [ALERT] 231/145705 (138738) : Starting frontend main: cannot bind socket [0.0.0.0:80] . . . Aug 19 14:57:05 92214d8ff5e2 systemd[1]: Failed to start HAProxy Load Balancer.

      This example systemctl output includes some highlighted lines from the systemd journal that describes the error. These lines give you all the information about the error that you need to troubleshoot it further. Specifically, the line cannot bind socket [0.0.0.0:80] describes the socket that HAProxy is trying to use (0.0.0.0:80), so you can skip the following journalctl steps and instead proceed to the Troubleshooting with ss and ps Utilities section at the end of this tutorial. The other highlighted line indicates the status of the HAProxy process, which in the case of a cannot bind socket error will show Failed to start HAProxy Load Balancer.

      If your systemctl output does not give specific information about the IP address and port or ports that are causing the error (if you are using Ubuntu or Debian then this applies), then you will need to examine journalctl output from the systemd logs. The following section explains how to use journalctl to troubleshoot a cannot bind socket error.

      Troubleshooting Using journalctl Logs

      If your systemctl output does not include specifics about a cannot bind socket error, you should proceed with using the journalctl command to examine systemd logs for HAProxy.

      On Ubuntu and Debian-derived systems, run the following command:

      • sudo journalctl -u haproxy.service --since today --no-pager

      On CentOS, Fedora, and RedHat-derived systems, use this command to inspect the logs:

      • sudo journalctl -u haproxy.service --since today --no-pager

      The --since today flag will limit the output of the command to log entries beginning at 00:00:00 of the current day only. Using this option will help restrict the volume of log entries that you need to examine when checking for errors.

      If HAProxy is unable to bind to a port that is in use, search through the output for lines that are similar to the following log entries, specifically lines that contain the cannot bind socket error message as highlighted in this example:

      Output

      -- Logs begin at Wed 2020-08-19 19:38:12 UTC, end at Wed 2020-08-19 19:53:53 UTC. -- . . . Aug 19 19:39:21 92214d8ff5e2 systemd[1]: Starting HAProxy Load Balancer... Aug 19 19:39:21 92214d8ff5e2 haproxy[135]: [ALERT] 231/193921 (135) : Starting frontend main: cannot bind socket [0.0.0.0:80] Aug 19 19:39:21 92214d8ff5e2 haproxy[135]: [ALERT] 231/193921 (135) : Starting frontend main: cannot bind socket [:::80] Aug 19 19:39:21 92214d8ff5e2 systemd[1]: haproxy.service: Main process exited, code=exited, status=1/FAILURE Aug 19 19:39:21 92214d8ff5e2 systemd[1]: haproxy.service: Failed with result 'exit-code'. Aug 19 19:39:21 92214d8ff5e2 systemd[1]: Failed to start HAProxy Load Balancer. . . .

      The first highlighted line of output indicates that HAProxy cannot bind to port 80 on all available IPv4 interfaces (denoted by the 0.0.0.0 IP address). Depending on your system’s configuration, the IP addresses may be different and only show individual IPs.

      If you are using HAProxy with IPv6, then the output may also include a line like the second one that is highlighted with an IPv6 specific interface and port error, in this case :::80. The first two :: characters indicate all available IPv6 interfaces, while the trailing :80 indicates the port.

      Even though your own system may have different conflicting interfaces and ports, the errors will be similar to the output shown here. With this output from journalctl you will be able to diagnose the issue using ss, ps, and ip commands in the following section of this tutorial.

      Troubleshooting with ss and ps Utilities

      To troubleshoot a cannot bind socket error you need to determine what other process is listening on the IP address and port that HAProxy is attempting to use, or if the IP address is available to HAProxy.

      For example, if another server like Nginx is configured to listen on port 8080 on all available IPv4 network interfaces, the full socket would be 0.0.0.0:8080. If HAProxy is also configured to use 0.0.0.0:8080 then the operating system will throw an EADDRINUSE error, and HAProxy will show a cannot bind socket error message, since it cannot claim the socket for itself.

      In the previous journalctl section, something was already bound to all the available IPv4 addresses (denoted by 0.0.0.0:80). Most modern Linux distributions include a utility called ss which can be used to gather information about the state of a system’s network sockets.

      The following command will determine the name of the process that is already bound to an IPv4 interface on port 80. Ensure that you substitute the port from the error message if it is different from 80 in the following command:

      • sudo ss -4 -tlnp | grep 80

      The flags to the ss command alter its default output in the following ways:

      • -4 restricts ss to only display IPv4-related socket information.
      • -t restricts the output to tcp sockets only.
      • -l displays all listening sockets with the -4 and -t restrictions taken into account.
      • -n ensures that port numbers are displayed, as opposed to protocol names like ‘httporhttps`. This is important since HAProxy may be attempting to bind to a non-standard port and a service name can be confusing as opposed to the actual port number.
      • -p outputs information about the process that is bound to a port.
      • | grep 80 limits the output to lines that contain the characters 80 so there are fewer lines that you have to examine

      Note: in this IPv4 and the following IPv6 example, if you do not have a line in your output with a matching port, then your cannot bind socket error may be derived from an EADDRNOTAVAIL error. Skip to the next section Troubleshooting with the ip Utility to examine the available IP addresses on your system.

      With all of those flags, you should receive output like the following:

      Output

      LISTEN 0 511 0.0.0.0:80 0.0.0.0:* users:(("nginx",pid=40,fd=6))

      The first three fields are not important when troubleshooting a cannot bind socket error so they can be ignored. The important fields are the fourth (0.0.0.0:80), which matches the journalctl error that you discovered earlier, along with the last users:(("nginx",pid=40,fd=6)), specifically the pid=40 portion.

      If you have a cannot bind socket error that is related to an IPv6 interface, repeat the ss invocation, this time using the -6 flag to restrict the interfaces to the IPv6 network stack like this:

      • sudo ss -6 -tlnp |grep 80

      The -6 flag limits the ip command to IPv6 interfaces. If HAProxy is unable to bind to an IPv6 socket, you should have output like the following:

      Output

      LISTEN 0 511 [::]:80 [::]:* users:(("nginx",pid=40,fd=7))

      Again, substitute the port number in question from your journalctl output if it is different from the highlighted 80 given here.

      In both these cases of IPv4 and IPv6 errors, the ss output indicates that there is a program with process ID 40 (the pid=40 in the output) that is bound to the 0.0.0.0:80 and [::]:80 interfaces respectively. This process is preventing HAProxy from starting since it already owns the port. To determine the name of the program, use the ps utility like this, substituting the process ID from your output in place of the highlighted 40 value in this example:

      You will receive output that is similar to the following:

      Output

      PID TTY TIME CMD 40 ? 00:00:00 nginx

      The highlighted nginx in the output is the name of the process that is listening on the interfaces. Now that you have the name of the program that is preventing HAProxy from starting, you can decide how to resolve the error. You could stop the nginx process, reconfigure nginx to listen on a different interface and port, or reconfigure HAProxy to avoid the port collision.

      It is important to note that the process may be different from nginx and the port and IP addresses may not always be 0.0.0.0 or [::] if you are diagnosing a cannot bind socket error. Oftentimes, different web servers and proxies will be in use on the same server. Each may be attempting to bind to different IPv4 ports and IPv6 interfaces to handle different web traffic. For example, a server that is configured with HAProxy listening on the IPv4 loopback address (also referred to as localhost) on port 8080 will show ss output like this:

      Output

      LISTEN 0 2000 127.0.0.1:8080 0.0.0.0:* users:(("haproxy",pid=545,fd=7))

      It is important to combine systemctl output, or journalctl output that indicates specific IP addresses and ports, with diagnostic data from ss, and then ps to narrow down the process that is causing HAProxy to fail to start.

      Sometimes when you are troubleshooting a cannot bind socket error message with ss and ps there will not be any output at all, which means that the error may not be caused by a socket conflict. The next section of this tutorial explains how to troubleshoot a cannot bind socket error using the ip utility.

      Troubleshooting with the ip Utility

      The previous section explained how an EADDRINUSE operating system error could cause a cannot bind socket error message. However, if you have examined ss and ps output and there is no socket conflict on your system, the issue may be caused by an EADDRNOTAVAIL operating system error instead. In this case HAProxy may be trying to bind to a socket that is not available to your operating system.

      To determine whether a cannot bind socket error is caused by an EADDRNOTAVAIL, examine both the IPv4 and IPv6 network interfaces on your system using the ip command.

      • sudo ip -4 -c address show
      • -4 restricts ip to only display IPv4-related interface information.
      • -c adds color coding to the output so that it is easier to parse visually.
      • address show displays the IP address for an interface, with the -4 and -c flags taken into account.

      You should receive output that looks similar to the following on any Linux distribution that includes the ip tool:

      Output

      1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 qdisc noqueue state UNKNOWN group default qlen 1000 inet 127.0.0.1/8 scope host lo valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 inet 203.0.113.1/24 brd 203.0.113.255 scope global eth0 valid_lft forever preferred_lft forever inet 192.0.2.1/24 brd 192.0.2.255 scope global eth0 valid_lft forever preferred_lft forever 3: eth1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc fq_codel state UP group default qlen 1000 inet 198.51.100.1/24 brd 198.51.100.255 scope global eth1 valid_lft forever preferred_lft forever

      Make a note of your IP addresses that correspond to the highlighted examples in this output. Your IP addresses and network interfaces will be different than the examples shown here. You may have more or fewer interfaces, and each may have more or fewer addresses assigned to them. The important part is to note the IP addresses from ip.

      To examine IPv6 addresses that are assigned to your system, use the ip command with the -6 flag like this:

      • sudo ip -6 -c address show

      You should receive output like the following:

      Output

      1: lo: <LOOPBACK,UP,LOWER_UP> mtu 65536 state UNKNOWN qlen 1000 inet6 ::1/128 scope host valid_lft forever preferred_lft forever 2: eth0: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 state UP qlen 1000 inet6 2604:a880:400:d1::3d3:6001/64 scope global valid_lft forever preferred_lft forever inet6 fe80::a4ff:aaff:fec9:24f8/64 scope link valid_lft forever preferred_lft forever

      Again note the highlighted values in this example output and look for the corresponding IPv6 addresses in your output.

      Once you have a list of addresses that are assigned to your system, you can try to find a matching IP address that corresponds to the cannot bind socket [x.x.x.x:80] error. If there is no IP address that matches, then HAProxy is likely configured to use an IP address that is not available to your system and the cannot bind socket error is being caused by the operating system throwing an EADDRNOTAVAIL error.

      To resolve the error you will need to edit your /etc/haproxy/haproxy.cfg file and change the bind address or addresses to an IP address that is available to your system based on the output of the ip command.

      For example, if /etc/haproxy/haproxy.cfg contained a bind line like the following using 198.51.100.123 as the IP address, but your system has 198.51.100.1 assigned based on the example output above, you will need to edit the bind line.

      Following this hypothetical example, this haproxy.cfg snippet shows the invalid IP address:

      /etc/haproxy/haproxy.cfg

      . . .
      frontend main
              bind 198.51.100.123:80
      

      A correct bind line that matches the IP address in the example ip output would look like this:

      /etc/haproxy/haproxy.cfg

      . . .
      frontend main
              bind 198.51.100.1:80
      

      Once you have edited /etc/haproxy/haproxy.cfg with the correct IP address, restart it using the systemctl command:

      • sudo systemctl restart haproxy.service

      Now examine HAProxy’s status and make sure that the output shows an active (running) line:

      • sudo systemctl status haproxy.service

      Output

      ● haproxy.service - HAProxy Load Balancer Loaded: loaded (/lib/systemd/system/haproxy.service; enabled; vendor preset: enabled) Active: active (running) since Wed 2020-08-19 21:31:46 UTC; 17h ago Docs: man:haproxy(1) file:/usr/share/doc/haproxy/configuration.txt.gz Process: 487 ExecStartPre=/usr/sbin/haproxy -f $CONFIG -c -q $EXTRAOPTS (code=exited, status=0/SUCCESS) . . . Aug 19 21:31:46 d6cdd0c71489 systemd[1]: Started HAProxy Load Balancer.

      If you have resolved the cannot bind socket error your output should be similar to this example output. The highlighted lines that show HAProxy is active, and that the process was started successfully.

      Conclusion

      In this tutorial you learned how to troubleshoot an HAProxy cannot bind socket error message on both IPv4 and IPv6 interfaces. You learned how to use systemctl to examine the status of the HAProxy server and try to find error messages. You also learned how to use journalctl to examine the systemd logs for specific information about a cannot bind socket error.

      With the appropriate error messages from the systemd logs, you then learned about the ss utility and how to use it to examine the state of a system’s network sockets. After that you learned how to combine process ID information from ss with the ps utility to find the name of the process that is causing HAProxy to be unable to start.

      Finally, in the case of a cannot bind socket error that is related to an unavailable IPv4 or IPv6 address, you learned how to use the ip utility to examine available network interfaces on your system.



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