According to http://expressionengine.com/user_guide/installation/installation.html, it says:

For most Unix hosts the following is typical, but you may check with your host to see if more restrictive permissions can be used to allow PHP to write to files (666) and folders (777). On Windows servers the following will not apply, but you will need to ensure that the files and folders are writable by ExpressionEngine. You may need to contact your host for this.

Not sure what this means. I can change the specific files and folders to 666 and 777 respectively where I am the chown'er, but the above sounds like I need to allow PHP to do this too?


I need to ensure that PHP can write to specific files (666) and folders (777).

How do I do this?

  • 2
    I am not sure what problem you are trying to solve? If you can access the directory where file is located and have execute permission in it you can write to files and directories with those permissions.
    – Karlson
    Apr 4, 2012 at 15:19
  • Added further details above. Apr 4, 2012 at 15:31
  • 1
    For most Unix hosts the following is typical, but you may check with your host to see if more restrictive permissions can be used to allow PHP to write to files (666) and folders (777) -- Is there a coma missing? otherwise this phrase doesn't make any sense. Unless higher level directory is restricted you have no issue writing to world writable files or directories.
    – Karlson
    Apr 4, 2012 at 15:39
  • I just did a copy and paste from the documentation. Plus, it's the reason why I posted the question as I don't understand what that quote means... Apr 4, 2012 at 15:55
  • 1
    If you see documentation suggesting that you use 666 or 777 in relation to web files, you should probably ignore it unless there is a good reason explained. It's usually something written by someone who couldn't figure out how to set up the right permissions, and gave up and gave everyone read or write access to the files.
    – jsbillings
    Apr 4, 2012 at 19:44

3 Answers 3


I will complete rahmu's and MV's answers with a technical solution. Everything that follows is valid for UNIX-like systems only.

Scroll past the chmod/chown section for an example using ACLs - a more powerful tool than UNIX file modes.

Finding your web server username

First, you will need to know the username under which your web server runs. If you are using Apache, it can be apache or httpd, www-data, etc. On most Debian-like systems, Apache is www-data. For nginx, generally, it is also www-data.

To check it out, try:

ps aux | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' | grep -v root | head -1 | cut -d\  -f1

Ensure that the username this command returns is coherent (for example, I use nginx 99% of time, but this command returns tomcat7, a Java web server I installed once).

Giving permissions to the web server: using chmod and chown

Doing a chmod of 666 or 777 (the go-to solution for that kind of problems in bad documentations/tutorials) can magically make things work, but is insecure. Giving 666 or 777 permissions will give access to "others". So not just Apache, but also grandmother and nsa (provided that those user accounts exist on your machine - but no really, please avoid doing this unless it's just for testing/troubleshooting).

It is better to be more specific and give permissions to just you and Apache. Change the group of your files to give the full control on your files to the web server. To do this, change the owner recursively:

chown -R www-data:www-data your/folder/

But most likely, you may want to keep full access on your files by changing the group only:

chown -R yourusername:www-data your/folder/

Then, do the appropriate chmod to give the group www-data the same permissions as you. For example, if the current mode is 640 (6 for you, 4 for www-data, 0 for others, translating to -rw-r-----), set it to 660 (6 for you, 6 for www-data, 0 for others, translating to -rw-rw----). See rahmu's answer to learn more about file modes, it's an old, however elegant mechanism.

To avoid manipulating arcane numbers with chmod, you can also use this syntax:

chmod -R g+rw your/folder/

It means "to the group (g), add (+) read and write (rw) permissions on folder your/folder/, recursively (-R)".

In 90% of cases, this should be enough.

My preferred method: using ACLs (Access Control List)

Sometimes the first solution is not sufficient. I will take the example of Symfony Framework that logs and caches a lot of data. So it needs write access to the appropriate folder.

And the chmod/chown method may not be sufficient, when you are using in parallel the Symfony Console in CLI (under my user account) and the Web (web server user). This causes a lot of problems because Symfony is constantly modifying permissions.

In this case, we will use the ACL (Access Control List), which is a more advanced way to manage permissions on many UNIX systems.

Here the commands given by the official Symfony documentation (please change app/cache and app/logs to your needs):

On a system that supports chmod +a (ie. not Debian/Ubuntu)

sudo chmod +a "www-data allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs
sudo chmod +a "`whoami` allow delete,write,append,file_inherit,directory_inherit" app/cache app/logs

On a system that does not support chmod +a (most common)

You will need the setfacl tool; maybe it is installed on your system by default, so try setfacl -v to see if the command is available.

If the command is not available, and you are using Ubuntu 14.04+, you'll just have to install the tool:

sudo apt install acl

Otherwise, follow your OS documentation, because you may need to change how your partition is mounted (Ubuntu documentation here).

And there we are:

sudo setfacl  -R -m u:"www-data":rwX -m u:`whoami`:rwX app/cache app/logs
sudo setfacl -dR -m u:"www-data":rwX -m u:`whoami`:rwX app/cache app/logs

I never had any problems with this method, satisfied or your money back.

  • 1
    +1 for 'ps aux | grep -E '[a]pache|[h]ttpd|[_]www|[w]ww-data|[n]ginx' | grep -v root | head -1 | cut -d\ -f1 ' May 26, 2016 at 12:39
  • 1
    i just added a added bounty, will award it to tis answer in 24 hours. UPVOTED, excellent answer, clearest on this subject that i have read to date. deserves bounty!
    – tony gil
    Oct 22, 2020 at 13:27
  • 1
    Thanks a lot @tonygil! Oct 26, 2020 at 10:35
  • thank you @MorganTouvereyQuilling - saved me in 2022 - excellent answer! Jun 17, 2022 at 6:09
  • @arbitrarily you're welcome! System administration matters like this don't age so fast, I expect this will stay the go-to answer for many more years! Jun 17, 2022 at 19:04

No matter who's the owner of the files, 666 permissions and 777 would be enough: the last digit makes sure that every user on the system has access. While this is the easiest way to do it, it is definitely not the safest for that exact reason.

A better way to do it

The first thing you need to understand is how Unix permissions work. In the interest of understanding the answer I gave at this link, please note that permissions can be translated to numbers:

  • 0: ---
  • 1: --x
  • 2: -w-
  • 3: -wx
  • 4: r--
  • 5: r-x
  • 6: rw-
  • 7: rwx

A chmod 666 is then equivalent to changing permissions to rw-rw-rw.

Next you have to figure out which is the user that is executing the PHP script. Normally that would be the user running your web server. Here's an example of how to do this (you can replace Apache with the name of your web server).

Once you know which is the user executing the scripts, and which's the owner of the files you mention, it is up to you to set appropriate permissions. Keep in mind that giving write access (even read) to every user on your system can be potentially disastrous.

  • It's good to note that the numerical representation of the rights comes from the binary numeral system where you use only 0 and 1. Each bit has a corresponding value in decimal, which can be calculated easily starting from the rightmost bit, by using "2 to the power of" 0, 1, 2 and so on going to the left. So, a binary number 101 will be decimal 5. So, we see that eXecute is the rightmost bit and hence has a value of 1. The Write is the second bit with a value of 2 and Read has a value of 4. When you combine Read and Write you get 4+2+0 = 6. Then user, group and for others are combined. Feb 25, 2021 at 9:45

Expression Engine is just like many other PHP web applications which need read+write access to some files and directories. For example, EE requires write access to its config.php and database.php files, and write access to its file upload directories.

What the documentation is stating is that, as most servers run PHP as mod_php (and so run with the permissions of the web server), and as you probably will upload your files with FTP (or similar) using your own user, those files and directories will need to be given permissions 666 (everybody can read and write) and 777 (everybody can read, write and browse).

That is not the safest way, but certainly is the easiest, specially if your are using a hosting service.

However, as the EE instructions state, ask your hosting provider, because some don't use mod_php but a fastcgi, suphp or different version. Those servers run PHP as your own user, so all files you upload are already readable and writable by PHP and by any file created by the EE scripts. In that case files and directories accessed by PHP would need to be given 600 and 700 access. Other files to be accessed directly by the web server (not the PHP runtime) would still need 666 and 777 access).

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