When securing Memcache for your Drupal installation, the first challenge is locating the correct configuration file. The file location varies significantly between Linux distributions:

# Debian/Ubuntu: 
/etc/memcached.conf

# RHEL/CentOS: 
/etc/sysconfig/memcached

# Arch Linux: 
/etc/conf.d/memcached

# Custom installations may use: 
/usr/local/etc/memcached.conf

Try these commands to locate your active configuration:

# Check running process arguments
ps aux | grep memcached

# Search common locations
sudo find / -name "*memcache*" -type f

If no configuration exists, you can safely create one. Here's a secure baseline configuration for Drupal:

# /etc/memcached.conf
# Listen only on localhost by default
-l 127.0.0.1

# Memory allocation (adjust for your server)
-m 64

# Maximum connections
-c 1024

# Disable UDP protocol (security best practice)
-U 0

# Verbose logging for troubleshooting
-vv

When Drupal and Memcache run on separate servers, bind to a specific interface:

# Replace with your internal network IP
-l 192.168.1.100

# Then restrict access with iptables:
sudo iptables -A INPUT -p tcp --dport 11211 -s 192.168.1.0/24 -j ACCEPT
sudo iptables -A INPUT -p tcp --dport 11211 -j DROP

After modifying the configuration, restart Memcache and verify:

# Ubuntu/Debian
sudo systemctl restart memcached

# Check listening ports
netstat -tulnp | grep memcached

# Test connectivity
telnet 127.0.0.1 11211
stats

In your Drupal settings.php, add these security-conscious configurations:

$conf['memcache_servers'] = ['127.0.0.1:11211' => 'default'];
$conf['memcache_key_prefix'] = 'your_unique_prefix_'; 
$conf['memcache_options'] = [
  Memcached::OPT_BINARY_PROTOCOL => TRUE,
  Memcached::OPT_TCP_NODELAY => TRUE,
  Memcached::OPT_RETRY_TIMEOUT => 2,
];

Implement these security monitoring practices:

# Regular log checks
grep -i "error\|warning\|failed" /var/log/memcached.log

# Automated monitoring script example:
#!/bin/bash
if ! nc -z 127.0.0.1 11211; then
  echo "Memcache down!" | mail -s "Alert" admin@example.com
fi

For connection problems, check these diagnostic commands:

# Check if Memcache is running
sudo systemctl status memcached

# Check port accessibility
telnet your_server_ip 11211

# Verify Drupal can connect
drush eval "print_r(drupal_map_assoc(memcache_get_stats()));"

When securing Memcache for Drupal implementations, the configuration file location varies significantly between Linux distributions:

# For RHEL/CentOS systems:
/etc/sysconfig/memcached

# For Debian/Ubuntu systems:
/etc/memcached.conf

# For custom compiled installations:
/usr/local/etc/memcached.conf

If the configuration file doesn't exist in standard locations, you can safely create it. Here's a basic template for Debian-based systems:

# Example /etc/memcached.conf
# Listen on localhost only (recommended for security)
-l 127.0.0.1
# Standard Memcache port
-p 11211
# Memory allocation (adjust based on your needs)
-m 64
# Maximum number of simultaneous connections
-c 1024

If you're unsure where Memcache is loading its configuration from, try these diagnostic commands:

# Check running process parameters
ps aux | grep memcached

# For systemd services:
systemctl status memcached
journalctl -u memcached

# Check which configuration file was loaded (if any)
memcached -h | grep "config file"

For Drupal implementations, consider these additional security measures:

# In settings.php for Drupal
$settings['memcache']['servers'] = ['127.0.0.1:11211' => 'default'];
$settings['memcache']['key_prefix'] = 'your_unique_prefix_';
$settings['memcache']['stampede_protection'] = TRUE;

After making changes, verify your Memcache binding:

# Check listening ports
netstat -tulnp | grep memcached
# Should show: tcp 0 0 127.0.0.1:11211 0.0.0.0:* LISTEN

# Test connectivity
telnet 127.0.0.1 11211
stats

Beyond security, consider these performance tweaks for Drupal:

# In /etc/memcached.conf
# Adjust slab sizes based on your content
-I 1m
# Enable large memory pages
-L
# Increase item size limit
-P

For comprehensive documentation, refer to the official Memcached Wiki and Drupal Memcache documentation.