My website is about copying files. Instead of copy the files to avoid to much time and server lagging, I decided to use overlayfs. The code mount the folder to the location specified in the terminal using the PHP interpreter. But, when I run the php script from Apache the script does not mount the overlay. And the worst is that there is no error output so I can debug what's wrong. I checked the php error log, no output about what happened.
The destination i'm mounting the overlayfs is to another user. For that I need root to execute the mount command. To be able to run the code without using root nor sudo, I took a look at this question. I created the c code, compile it and set the proper permissions (root.root, rwsr,sr...). I ran the code in a php file:
<?php
// filename over.php
print shell_exec("whoami")."\n";
print shell_exec('/var/www/vhosts/user/deployment/exec "sudo mount -t overlay overlay -o lowerdir=/var/www/vhosts/user/deployment/template5_dev,upperdir=/var/www/vhosts/user.deve/httpdocs,workdir=/var/www/vhosts/user/deployment/overlay-work /var/www/vhosts/user.deve/httpdocs"');
What the code does is print the actual user name (to make sure I have an output, to see if the code executed) then merge the folders. The file /var/www/vhosts/user/deployment/exec is the c program then I pass the code to execute as argument.
In the terminal I run: php -f "/var/www/vhosts/user/httpdocs/over.php". I check the merged folder I can see it works. And the output is user.
Then I unmount the overlay sudo umount /var/www/vhosts/user.deve/httpdocs.
I access the php script via the browser, I got the output user but the folder does not merge. I ctrl-f5 multiple times but nothing, no error, no error in log nothing.
I changed the command to shell_exec('/var/www/vhosts/user/deployment/exec "sudo mkdir /var/www/vhosts/user.deve/httpdocs/nouvo"');, the sudo created the folder from the browser.
I noticed that only the mount command does not run properly.
What could be the reason the sudo mount command does not run by apache, and even if there was an error, doesn't it print out the error?
I just take a look at /var/log/kern.log. I can see the mount command got executed from the web-browser. But the log is different from the one the ones executed in the terminal.
From the web-browser:
kernel: [ 149.465459] overlayfs: filesystem on '/var/www/vhosts/user.deve/httpdocs' not supported as upperdir
kernel: [ 151.629192] overlayfs: filesystem on '/var/www/vhosts/user.deve/httpdocs' not supported as upperdir
kernel: [ 153.453612] overlayfs: filesystem on '/var/www/vhosts/user.deve/httpdocs' not supported as upperdir
From the terminal after executing from the browser:
kernel: [ 312.858797] overlayfs: upperdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
kernel: [ 312.858804] overlayfs: workdir is in-use as upperdir/workdir of another mount, accessing files from both mounts will result in undefined behavior.
I just don't get the log from the browser since the script is same.
