Increase NFS Client Mount Point Security For a Web-Server noexec, nosuid, nodev Options


am using NFS server version 4.x on a CentOS/RHEL based system. I’m mounting my shared /var/www/ directory on five Apache based nodes using the following syntax:

mount -t nfs4 -o rw,intr,hard,proto=tcp rocknas02:/httproot/www /var/www/

I noticed that due to bug in my app user can sometime upload executable or other device files to get out of chrooted Apache server. How can I prevent such security issues on a CentOS or RHEL based NFS client and sever setup?


First, you need to fix your application. Next, you can pass the following three options to mount command to increase overall security on Apache/Nginx/Lighttpd nfs based client:

noexec – Prevents execution of binaries on mounted file systems. This prevents remote users from executing unwanted binaries on your system.

nosuid – Disables set-user-identifier or set-group-identifier bits. This prevents remote users from gaining higher privileges by running a setuid program.

nodev – Prevents character and block special devices from being defined, or if they exist, from being used as character and block special devices. This prevents remote users from getting out of chrooted server jails.

Modify your mount command as follows:

# mount -t nfs4 -o rw,intr,hard,proto=tcp,nodev,noexec,nosuid rocknas02:/httproot/www /var/www/


OR attempt to remount an already-mounted nfsv4.0 filesystem:

# mount -t nfs4 -o remount,rw,intr,hard,proto=tcp,nodev,noexec,nosuid rocknas02:/httproot/www /var/www/

Test it

To verify new settings, enter:

# mount

# mount | grep rocknas02


Sample outputs:

rocknas02:/httproot/www on /var/www type nfs4 (rw,noexec,nosuid,nodev,sync,intr,hard,proto=tcp,addr=,clientaddr=

Copy /bin/ls to rocknas02:/httproot/www i.e. type the following on your nfsv4.0 server called rocknas02

# cp /bin/ls /httproot/www


On client, type:

cd /var/www


run /bin/ls

ls -l


# Run uploaded ls


Sample outputs:

Fig. 01: Running ls command on nfs client


Updating /etc/fstab is left as an exercise for the reader.

Mount the filesystem read-only

If possible mount the filesystem in read-only mode. Modify your mount command as follows:

# mount -t nfs4 -o ro,intr,hard,proto=tcp,nodev,noexec,nosuid rocknas02:/httproot/www /var/www/


OR attempt to remount an already-mounted nfsv4.0 filesystem:

# mount -t nfs4 -o remount,ro,intr,hard,proto=tcp,nodev,noexec,nosuid rocknas02:/httproot/www /var/www/

Recommend file/directory permission for Apache

I suggest the following schema:

Run Apache as apache user and group

You must run httpd as root initially and it will switch to apache user and group:

# egrep -i  ^(User|Group)  /etc/httpd/conf/httpd.conf


Sample outputs:

User apache

Group apache

NFS server file/directory permission for /var/www/

Create a user called www-files using useradd command:

# useradd -d /var/www -M -s /sbin/nologin www-files


Make sure you lock www-files account using passwd command:

# passwd -l www-files


Change file owner and group to www-files for /var/www directory use the following passwd command:

# chown -R www-files:www-files /var/www/


Finally changes the file mode bits of each given file and directory according to mode:

By default all files & dirs permissions are set to read-only ###

chmod -R 0444 /var/www


Allow, apache/nginx/lighttpd to serve files from directory by settings others to x bit ###

find /var/www -type d -print0 | xargs -0 -I {} chmod 0445  {}


Optional certain directory may need additional permissions such as /var/www/uploads ###

#chmod  0777 -R /var/www/uploads

Use ls -l command to verify file permissions:

# cd /var/www

# ls -l


Sample outputs:

total 32

-r–r–r–. 1 www-files www-files  606 Dec 21  2011 best_resources.php

-r–r–r–. 1 www-files www-files 1068 Sep  4  2011 cdn_info_linux_unix_setup.php

dr–r–r-x. 2 www-files www-files 4096 Aug  5  2012 data


-r–r–r–. 1 www-files www-files 1550 Jun 22  2012 service-per-vm-guide.php

See also

How to configure php to deny file uploads.

This entry is 15 of 15 in the Linux / UNIX NFS File Server Tutorial series. Keep reading the rest of the series:

CentOS / Redhat: Setup NFS v4.0 File Server

Debian / Ubuntu Linux: Setup NFSv4 File Server

Mac Os X: Mount NFS Share / Set an NFS Client

RHEL: How Do I Start and Stop NFS Service?

How To Restart Linux NFS Server Properly When Network Become Unavailable

Linux Iptables Allow NFS Clients to Access the NFS Server

Debian / Ubuntu Linux Disable / Remove All NFS Services

Linux: Tune NFS Performance

Mount NFS file system over a slow and busy network

Linux Track NFS Directory / Disk I/O Stats

Linux Disable / Remove All NFS Services

Linux: NFS4 mount Error reason given by server: No such file or directory

Linux NFS Mount: wrong fs type, bad option, bad superblock on fs2:/data3 Error And Solution

CentOS / RHEL CacheFS: Speed Up Network File System (NFS) File Access

Increase NFS Client Mount Point Security



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