PHP文件上传报错UPLOAD_ERR_NO_TMP_DIR（错误码6）求助

Hey there, let's troubleshoot this upload error step by step. Since you haven't changed any configs and sys_get_temp_dir() correctly returns /tmp, the issue is almost certainly related to filesystem permissions, resource limits, or security restrictions—here's what to check:

1. Verify /tmp Directory Permissions & Ownership #

PHP needs write access to the temp directory to store uploaded files temporarily.

• Log into your server and run this command to check /tmp's status:

  ls -ld /tmp
  

  The output should show permissions drwxrwxrwt (the t is the sticky bit, which is critical for secure temp directory behavior) and owner/group as root:root.
• If permissions are incorrect, fix them with:

  chmod 1777 /tmp
  

  This sets the standard, secure permissions that allow all users to write to /tmp while preventing unintended file deletion by non-owners.

2. Check if /tmp is Full or Out of Inodes #

Even with correct permissions, a full filesystem or exhausted inodes will block new file creation:

• Check disk space usage for /tmp:

  df -h /tmp
  

• Check inode usage (each file/directory uses one inode):

  df -i /tmp
  

• If either is full, clean up old files in /tmp. For example, delete files older than 7 days to free up space:

  find /tmp -type f -mtime +7 -delete
  

3. Check PHP's open_basedir Restriction #

The open_basedir setting can limit which directories PHP can access, even if sys_get_temp_dir() returns /tmp:

• Open your php.ini file (location varies by server—common paths are /etc/php/<version>/fpm/php.ini or /etc/php/<version>/apache2/php.ini).
• Look for the open_basedir line. If it's set, make sure /tmp is included in the list of allowed directories (e.g., open_basedir = /var/www/html/:/tmp/).
• Save the file and restart your PHP service (e.g., systemctl restart php8.2-fpm) or web server to apply changes.

4. Check SELinux Policies (For Linux Servers With SELinux Enabled) #

SELinux can block web server processes from writing to /tmp even with correct filesystem permissions:

• Temporarily disable SELinux to test if it's the cause:

  setenforce 0
  

• Try uploading a file again. If it works, adjust SELinux policies instead of leaving it disabled:
  • For Apache:

    setsebool -P httpd_unified 1
    

  • For Nginx:

    setsebool -P nginx_unified 1
    

  The -P flag makes the change persistent across server reboots.

5. Quick Check: File Size Limits (Just to Rule Out) #

While your 91kb file is way below typical limits, it's worth confirming these php.ini settings are set appropriately:

• upload_max_filesize = 2M (more than enough for your file)
• post_max_size = 8M (should be larger than upload_max_filesize)
• Restart PHP/web server after any changes.

After trying these steps, test your file upload again—this should resolve the UPLOAD_ERR_NO_TMP_DIR issue.

内容的提问来源于stack exchange，提问作者Mark