Mount Setting (option)

In many experimental setups, tasks are often distributed across multiple servers, such as:

• DAQ Server: Handles the DAQ process.
• File Server: Stores experimental data.
• Analysis Server: Performs data analysis.

To simplify workflows, NFS (Network File System) can be used to allow the analysis server to access data directly from the file server without duplicating files. Additionally, external storage devices can be mounted for offline analysis to store data or generated ROOT files.

Configuring the File Server for NFS

Step 1: Install NFS Server Utilities

sudo apt update
sudo apt install nfs-kernel-server

Step 2: Configure Shared Directories in /etc/exports

1. Edit the /etc/exports file:

   sudo vi /etc/exports
   

2. Add an entry for the directory to share:

   /path/to/shared/data <client_ip>(ro,sync,subtree_check)
   

   • Replace /path/to/shared/data with the directory you want to share.
   • Replace <client_ip> with the IP address or subnet (e.g., 192.168.1.*).

3. Common options in /etc/exports

   Option	Description
   rw	Allows read and write access.
   ro (default)	Allows read-only access.
   sync (default)	Commits changes to disk before notifying the client. This ensures data integrity but may slightly reduce speed.
   async	Allows the server to reply to requests before changes are committed to disk. This improves speed but risks data corruption in case of failure.
   subtree_check (default)	Ensures proper permissions for subdirectories but may reduce performance.
   no_subtree_check	Disables subtree checks for better performance but reduces strict access control.
   wdelay (default)	Delays disk writes to combine operations for better performance. Improves performance but increases the risk of data loss during failures.
   no_wdelay	Disables delays for immediate write operations, reducing risk of data loss but potentially decreasing performance.
   hide	Prevents overlapping mounts from being visible to clients. Enhances security by hiding overlapping mounts.
   nohide	Allows visibility of overlapping mounts. Useful for nested exports but can lead to confusion.
   root_squash (default)	Maps the root user of the client to a non-privileged user on the server. Improves security by preventing root-level changes.
   no_root_squash	Allows the root user of the client to have root-level access on the server. This is not recommended unless absolutely necessary.
   all_squash	Maps all client users to a single anonymous user on the server. Useful for shared directories with limited permissions.

4. Save and exit the editor.

Step 3: Apply Changes and Start NFS Server

sudo exportfs -a
sudo systemctl enable nfs-server
sudo systemctl start nfs-server

Configuring the Analysis Server for Mounting

1. Mounting a Shared Directory via NFS

Step 1: Install NFS Utilities:

sudo apt update
sudo apt install nfs-common

Step 2: Create a Mount Point:

sudo mkdir -p /mnt/data

Step 3: Configure Persistent Mounting:

sudo vi /etc/fstab

Add:

<file_server_ip>:/path/to/shared/data /mnt/data nfs defaults 0 0

Step 4: Apply and Verify:

sudo mount -a
df -h

2. Mounting External Storage (e.g., USB or HDD)

Step 1: Identify the Device:

lsblk

• Look for the device name (e.g., /dev/sdb1) in the output.

Step 2: Create a Mount Point:

sudo mkdir -p /mnt/external

Step 3: Configure Persistent Mounting:

sudo vi /etc/fstab

Add:

/dev/sdb1 /mnt/external ext4 defaults 0 0

• Replace /dev/sdb1 with the actual device name.
• Replace ext4 with the correct filesystem type (e.g., ext4, xfs, vfat).

Step 4: Apply and Verify:

sudo mount -a
df -h

Troubleshooting

• File Server Issues:

  • Ensure the NFS service is running on the file server:

  sudo systemctl status nfs-server
  

  • Verify the export list:

  showmount -e
  

• Analysis Server Issues:

  • Check the NFS mount status:

  sudo mount -v /mnt/data
  

  • Verify network connectivity between the analysis server and file server.

• External Storage Issues:

  • Unmount safety:

  sudo umount /mnt/external
  

  • Formatting uninitialized Storage:

  sudo mkfs.ext4 /dev/sdb1
  

  • Use UUIDs for reliable mounting to avoid issues with device naming (e.g., /dev/sdb1):

  sudo blkid /dev/sdb1
  

  Add to /etc/fstab:

  UUID=your-uuid-here /mnt/external ext4 defaults 0 0
  

Example Configuration

File Server (/etc/exports)

/data/shared 192.168.1.101(rw,sync,no_subtree_check)
/data/backup 192.168.1.102(ro,async,hide)

Analysis Server (/etc/fstab)

192.168.1.100:/data/shared /mnt/data nfs defaults 0 0
UUID=abc123-4567-89def /mnt/external ext4 defaults 0 0