How to Manage Mobile Devices and Swap Space on Linux Systems

Managing USB and External Storage Devices

When a USB flash drive or external hard drive is connected to a Linux system, it appears as a block device such as /dev/sdX. The device must be mounted before use and unmounted before removal to avoid data loss.

Verify detection with lsusb or by monitoring system logs ( tail -f /var/log/syslog on Ubuntu, tail -f /var/log/messages on CentOS). If the device uses the NTFS filesystem, install the ntfs-3g package ( apt install ntfs-3g on Ubuntu, yum install ntfs-3g on CentOS) to enable read/write support.

Swap Space Overview

Swap is a special filesystem that moves inactive memory pages to disk, freeing RAM. It is slower than RAM, so it is optional on systems with sufficient memory. The kernel parameter /proc/sys/vm/swappiness controls swap aggressiveness; the default value 60 starts swapping when memory usage reaches roughly 40%.

Swappiness 0 – use swap only when memory is almost full.

Swappiness 100 – aggressively use swap.

Creating Swap Using a Dedicated Partition

Create a new partition with fdisk or gdisk.

Format the partition as swap: sudo mkswap /dev/sdb1.

Activate the swap partition: sudo swapon /dev/sdb1.

Verify activation: swapon -s.

Add a persistent entry to /etc/fstab:

/dev/sdb1  none  swap  sw  0  0

Creating Swap Using a Swap File

Create a zero‑filled file of the desired size: dd if=/dev/zero of=swapfile bs=1G count=1 Restrict permissions: chmod 600 swapfile.

Initialize the file as swap: sudo mkswap swapfile.

Enable the swap file: sudo swapon swapfile and verify with swapon -s.

Persist across reboots by adding to /etc/fstab: /home/ehigh/swapfile none swap sw 0 0 Swap files work because the OS treats any properly marked disk area as swap, regardless of whether it is a partition or a regular file. Using /dev/zero ensures the file is contiguous and contains no residual data.

Disabling Swap

To deactivate all swap devices, run swapoff -a.