beforeYouPostHereDidYouTry - Magento 1.x

This is a list of points you should check before posting your issue online. We've run into these issues before and know what the standard issues might be so please take the time to work them through

Basic debugging steps
Emails not sending
Product images not displaying
Cronjob not running

Basic checks when running into any issue

Thanks to an excellent answer by Ben Lessani (http://magento.stackexchange.com/a/429/50 < go upvote it) we have a basic checklist for any bug you run into.

###Logging Always check the Magento logs in var/log/..., also make sure it's turned on under System > Configuration > Developer > Log Settings and check the PHP and other related logs which are probably either located in your webshops root folder or in the /var/logs/ folder on the server.

Also check your developer console for any error logging on the frontend. It might be a javascript issue.

###Enable PHP Errors

This is key to most issues. For security or other reasons, PHP error display could likely be disabled by default by your PHP configuration.

You can enable errors with a more permanent solution, or merely something more temporary.

####Permanent solution

For Apache/mod_php users

In your document root's .htaccess file - just drop this at the top.

php_flag display_startup_errors on
php_flag display_errors on
php_flag html_errors on
php_flag  log_errors on
php_value error_log  /home/path/public_html/var/log/system.log

For Nginx/FastCGI users

In your Nginx virtualhost configuration, in either the final location .php { directive, or in the fastcgi_params file (if you have one specified)

fastcgi_param PHP_VALUE  display_startup_errors=on;
fastcgi_param PHP_VALUE  display_errors=on;
fastcgi_param PHP_VALUE  html_errors=on;
fastcgi_param PHP_VALUE  log_errors=on;
fastcgi_param PHP_VALUE  error_log=/home/path/public_html/var/log/system.log;

####Temporary/Universal solution

For any platform

Edit the Magento bootstrap index.php in your document root and uncomment the following line:

###ini_set('display_errors', 1);

###Enable Developer Mode

When you've had an error and suddenly hit the "Error Report" page, and been given a seemingly useless error string like 1184257287824 - you've got a few options.

####Permanent solution

For Apache/mod_php users

In your document root .htaccess file - just drop this at the top.

SetEnv MAGE_IS_DEVELOPER_MODE true

For Nginx/fastcgi users

In your Nginx virtualhost configuration, in either the final location .php { directive, or in the fastcgi_params file (if you have one specified)

fastcgi_param MAGE_IS_DEVELOPER_MODE true;

####Temporary/Universal solution

Edit the Magento bootstrap index.php in your document root and either make the if statement always true, or enabled for your specific IP.

if (isset($_SERVER['MAGE_IS_DEVELOPER_MODE']) || true) {
  Mage::setIsDeveloperMode(true);
}

if (isset($_SERVER['MAGE_IS_DEVELOPER_MODE']) || $_SERVER['REMOTE_ADDR'] == 'my.ip.add.ress') {
  Mage::setIsDeveloperMode(true);
}

###Check your permissions

Incorrect permissions will cause a wealth of problems, a lot of which are not that easy to find at first glance.

For example.
If PHP cannot write to the ./media directory and you have JS combine enabled - Magento is unable to generate the combined file and associated unique URI for the media. So instead, what you'll find in your browser source code is a full server path to the media file /home/path/public_html/media/xxx

Otherwise, the site can appear to be functioning as normal - with no critical errors actually visible.

Please bear in mind, this practice is secure for dedicated hosting but may present security issues with shared hosting if the Apache process isn’t chroot’ed per user.

In our example, the SSH/FTP user is sonassi, the Apache user is apache and the group is apache

#####Add the FTP/SSH user to the Apache group

Most importantly, we need to make sure that the FTP/SSH user is part of the Apache group, in our example, its apache (but is also commonly www-data)

usermod -a -G apache sonassi

Keep adding as many users to the group as you have for FTP/SSH.

#####Reset original permissions

So before we start, lets make sure all the permissions are correct.

chown -R sonassi:apache /home/path/public_html/
find /home/path/public_html/ -type d -exec chmod 750 {} \;
find /home/path/public_html/ -type f -exec chmod 640 {} \;
chmod -R g+w /home/path/public_html/{includes,media,var}

####Making the changes permanent #####ACLs and Sticky Bits

ACLs in Linux allow us to define specific rules, in our case, what permissions files should inherit upon creation. A sticky bit (mentioned later) takes care of group inheritance, but does not help with the permissions, which is why we use ACLs.

Start by enabling ACL support on the active partition, please ensure your Kernel was compiled with ACL support.

Your partition may be /, /home, /var or something else, replace as appropriate.

mount -o remount,acl /home

Now ACLs are enabled, we can set the ACL rules and group sticky bits:

setfacl -R -d -m u::rwX,g::rwX,o::rX /home/path/public_html/
chmod g+s /home/path/public_html/

#####But I don’t have ACL support

If your Kernel doesn’t support ACLs you can also use umask (which is a run time setting for BASH, FTP and PHP) to set the default file permissions. Magento usually sets umask(0) in index.php, however, it would be in your interests to change this.

In your index.php change the umask line to be

umask(022);

And in your BASH environment for SSH, set this in either your .bashrc or .bash_profile

umask 022

For your FTP server, you’ll need to read the documentation for it, but the principle is the same.

###Revert theme to default

Its possible that either your theme or package is responsible for this issue. Reverting back to a vanilla Magento theme is a quick way to find out.

*This comes with the caveat that some modules may be dependent on certain theme features

Rather than change anything via the admin panel, it is much simpler to merely rename the offending directories.

Via SSH

mv ./app/design/frontend/myBrokenTheme{,.tmp}
mv ./skin/frontend/myBrokenTheme{,.tmp}

Or via your FTP client, traverse and rename your package to something else. eg. myBrokenTheme.tmp

####If this resolves your issue

Then you need to dig a bit deeper as to what part of the template is problematic. So restore your package and attempt the following, testing between each.

Essentially, the process is to gradually enable directories as you traverse down the file tree - until you can find the offending file.

Rename the layout directory to .tmp
Rename the template directory to .tmp

Then if either yields a fix, rename all files within the layout directory to .tmp - (for the SSH users ls | xargs -I {} mv {} {}.tmp or rename 's/^/.tmp/' *)

Then gradually enable each file 1 by 1 until resolved.

####If this doesn't resolve your issue

There is potential that your base/default or enterprise/default directories have become contaminated - and are best replaced with a known clean version.

You can do this by downloading a clean build of Magento and replacing your directories as necessary. Via SSH you can do this:

cd /home/path/public_html/
mkdir clean_mage
cd clean_mage
MAGENTO_VERSION=1.7.0.0
wget -O magento.tgz  http://www.magentocommerce.com/downloads/assets/$MAGENTO_VERSION/magento-$MAGENTO_VERSION.tar.gz
tar xvfz magento.tgz
cd /home/path/public_html/app/design/frontend
mv base{,.tmp}
cp -par /home/path/public_html/clean_mage/magento/app/design/frontend/base .
cd /home/path/public_html/skin/frontend
mv base{,.tmp}
cp -par /home/path/public_html/clean_mage/magento/skin/frontend/base .

You can also take the opportunity to diff the two directories if you want to verify any changes.

diff -r base base.tmp

NB. This method will cause more errors during the process, as module dependency dictates the existence of specific files. Unfortunately, its par for the course.

###Disable local modules

By default, Magento defines the PHP include path to load classes in the following order

Local > Community > Core

If a file is in Local - load it and do no more.
If a file is in community - load it and do no more.
If a file can't be found anywhere else - load it from the core.

Again, rather than disable modules via the Magento admin panel, it is more practical to do this at a file level.

Typically, to disable a module the "proper" way, you would edit the respective ./app/etc/modules/MyModule.xml file and set <active>false</active> - however, this doesn't actually prevent a class from loading.

If another class extends a given class in a module (ignoring any Magento dependency declarations), it will still be loaded - regardless of whether the extension is disabled or not.

So again, the best means to disable an extension is to rename the directory.

#####Begin by disabling local

Just rename the directory via FTP, or use the following SSH command

mv ./app/code/local{,.tmp}

#####Then disable community

mv ./app/code/community{,.tmp}

####If the issue is resolved from either

Then it is a case of understanding which module in particular the error stemmed from. As with the example given above for the package diagnosis, the same process applies.

So restore the X directory and attempt the following, testing between each.

Essentially, the process is to gradually enable directories (modules) one-by-one until the error re-occurs

Rename all the modules in the directory to .tmp (for the SSH users ls | xargs -I {} mv {} {}.tmp or rename 's/^/.tmp/' *)
Gradually enable each module one-by-one, by removing .tmp from the file name

####If the issue is not resolved

Then it is possible the core itself is contaminated. The main Magento PHP core consists of

./app/code/core
./lib

So again, rename these directories and copy in a clean variant. Assuming you already downloaded a clean version of Magento as above, via SSH, you can do this:

cd /home/path/public_html/app/code
mv core{,.tmp}
cp -par /home/path/public_html/clean_mage/magento/app/code/core .

Then if the issue still isn't resolved, replace the lib directory too

cd /home/path/public_html
mv lib{,.tmp}
cp -par /home/path/public_html/clean_mage/magento/lib .

At this point, your Magento store will be nothing more than a vanilla installation with a modified database.

Some models are actually still stored in the database (Eg. order increment) - so at this point, it becomes a case of manually making those edits. So far, all the steps above have been reversible with no lasting damage. But if we were in import a clean Magento database too - it could prove irreversible (short of restoring a backup).

The guide above serves to get you on your way to identifying an error; not to fixing the resultant error.

^{Content willingly sourced from www.sonassi.com/knowledge-base/magento-debug-process and www.sonassi.com/knowledge-base/stop-magento-permissions-errors-permanently}

Issue-specific solutions

Emails not sending

My (transactional) emails are not being sent

Are there any emails sent or just not the ones from the queue
Did you check the queue table if the e-mails are added to the queue correctly?
Do you use an module for sending emails?
Are you sending email via SMTP or Sendgrid etc and if so, is the SMTP or service working properly?
Did you check if contact form email is sending, is it just the transactional emails?
If sending via localhost, try to create a test script with the following code <?php mail('your@email.com', 'Test email', 'Test email'); ?> in your magento root and execute it from browser.
Did you check the mail log created by your server? Are the emails in there?
Check "Spam" folder in your email account.

Product images not displaying

Product images are not displaying on the front end

Check file permissions on media folder (775 for directory and 664 for files)
Check if the file owner is correct (could be root:root)
Flush first image cache and then regular cache

Cronjob not running

One or more, or all cronjobs in Magento fail to run

Install Aoe Scheduler to an overview of tasks
Empty the cron_schedule table and ensure Magento rebuilds it
Check config XMLs for syntax errors, a syntax error might cause cronjobs not to be picked up
Check logs and Aoe Scheduler for errors thrown in cronjobs. If one fails, the ones afterwards will too.
Call the cronjob method directly from a script ([Namespace]_[Module]_Model_Cron::theMethod()). Does it execute like expected?
Check if the cronjob in Linux has any issues using this answer http://stackoverflow.com/a/2264897/387136
For magento 1.8+ check if PHP function shell_exec is not disabled in php.ini