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References to Unix-like (*nix) commands in documentation or forum posts can be intimidating if you're not used to them, but sometimes "command line" is necessary for administering your system or fixing a problem.
Learning some of these *nix commands can help you be more productive, as well as give you insight into what your hosting control panel or GUI FTP client does.
There are a number of situations that might result in visitors accessing a Drupal site via a caching web proxy. Even though such caches are typically a good thing for sites, sometimes these caching schemes can have undesirable side effects and you may find that instructing proxy servers not to cache pages is the only solution to some problems. (You can learn more about web caches and how they work.)
Some problems that caches may cause with Drupal sites include:
A change that a user made to a page may not be reflected immediately, forcing the user to wait some time to see content they contributed (such as a comment) appear on the site.
User identities become confused. A user may login under their username but when they access another page, the proxy server sends the cached page from another user's session, effectively switching the identities of the user.
If you attempt to load admin/build/modules and get a blank page, a message that says "The requested page could not be found" or a server error, this is most likely a memory issue.
When viewing this page, modules are (since Drupal 5.x) only loaded if they are enabled (previously, even disabled modules were loaded). Even so, a fair amount of ancillary processing takes place on this page and can cause PHP to run out of available memory. Note that all modules' .info files are loaded whether or not the modules are enabled.
There are two fixes:
Increase PHP's memory limit, e.g. to set it to 16MB try one of these:
memory_limit = 16M to your system's main php.ini file (recommended, if you have access. In case you don't, you can try to upload your own php.ini file in the root folder of your Drupal installation, but bear in mind that this will only have an effect if PHP is running as CGI)
ini_set('memory_limit', '16M'); in your sites/default/settings.php file (this doesn't work on all servers)
php_value memory_limit 16M in your .htaccess file in the Drupal root (this only works if PHP is running as an Apache module)
With book.module default, "previous/up/next navigation" is displayed only at the bottom.
Is it possible to add "previous/up/next navigation" at the top, too?
I would like to make it selectable;
- bottom only (current default)
- top only
- both (bottm & top)