How to Manage USB Devices and Configure Swap Space on Linux

Mobile Device Management

Removable storage (USB flash drives, external hard disks) must be mounted before use and unmounted before removal to avoid data loss.

Detecting a USB storage device

When a USB device is plugged in, the kernel creates a SCSI device node under /dev, typically named /dev/sdX. Verify the detection with:

lsusb

Viewing kernel logs

Real‑time kernel messages show the device discovery process. Use the appropriate log file for your distribution:

# Ubuntu
 tail -f /var/log/syslog

# CentOS
 tail -f /var/log/messages

NTFS file‑system support

Linux cannot write to NTFS partitions without the ntfs-3g driver. Install it from the package manager:

# Ubuntu
 apt install ntfs-3g

# CentOS
 yum install ntfs-3g

Swap Space Management

Swap is a special area on disk used to store pages that are not actively used in RAM. The kernel parameter /proc/sys/vm/swappiness controls how aggressively the system uses swap.

Default swappiness = 60 (swap starts when RAM usage reaches ~40%).

Swappiness = 0 – swap is used only when RAM is almost exhausted.

Swappiness = 100 – the kernel uses swap aggressively.

Creating a swap partition

Create a new partition with fdisk or gdisk (e.g., /dev/sdb1).

Mark the partition type as Linux swap (type 82) and write the table.

Initialize the partition as swap: sudo mkswap /dev/sdb1 Activate the swap partition immediately: sudo swapon /dev/sdb1 Verify activation: swapon -s Add a persistent entry to /etc/fstab so the swap is enabled at boot:

/dev/sdb1 none swap sw 0 0

Creating a swap file

If there is no free partition space, a swap file can be created on an existing filesystem.

Create a file of the desired size (example: 1 GiB): dd if=/dev/zero of=/swapfile bs=1G count=1 Restrict permissions so only root can read/write: sudo chmod 600 /swapfile Mark the file as swap space: sudo mkswap /swapfile Enable the swap file immediately: sudo swapon /swapfile Verify that it is active: swapon -s Persist the swap file across reboots by adding to /etc/fstab:

/swapfile none swap sw 0 0

Disabling swap

To turn off all swap devices and files (useful for testing or when swap is no longer needed):

swapoff -a