Filesystems

Alpine Linux supports a number of filesystems.

Filesystem Tools

Alpine has multiple storage media formatting packages available. Different packages/programs are used to format different types of filesystems.

Tool	Filesystem	Brief Notes
btrfs-progs	Btrfs
dosfstools	FAT12/FAT16/FAT32
e2fsprogs	ext2/ext3/ext4	ext4 is current default
f2fs-tools	F2FS
hfsprogs	XFS HFS/HFS+	Apple/Mac products
jfsutils	JFS
ntfs-3g	NTFS	Microsoft/Windows FUSE driver
xfsprogs	XFS

Formatting Partitions

Whenever a partition is created, the partition must be formatted first before using it. Depending on the filesystem to be used, the necessary formatting tool for the filesystem must be installed first. The various formatting tools like mkfs.ext4, mkfs.vfat, mkfs.btrfs are part of file system tools dosfstools, e2fsprogs, btrfs-progs. Install the filesystem tools first, if not done already.

The following examples show how to use the formatting tools for different filesystems:

Warning: The /dev/sdXY is only an example. Make sure you choose the right partition to format! If you choose the wrong partition, your will lose your data. Make a backup first and do not proceed, if you are unsure.

e2fsprogs

ext4 is the default filesystem in Alpine Linux.

# mkfs.ext4 /dev/sdaXY

btrfs-progs

# mkfs.btrfs /dev/sdaXY

dosfstools

# mkfs.vfat /dev/sdaXY

f2fs-tools

# mkfs.f2fs /dev/sdaXY

Swap Partition

Swap space is used for two purposes

Extend the virtual memory beyond the installed physical memory (RAM) to avoid Out of memory condition
Suspend-to-disk or Hibernation support

Below Instructions explain how to use a seperate partition for swap:

The following commands prepares the unmounted partition (/dev/sda2) for swap space, activates the prepared swap space and starts the swap service to manage swap space immediately:

# mkswap /dev/sda2
# swapon /dev/sda2 
# rc-service swap start

The command free -m will show how much swap space is available (in MB).

To make the swap persistent across reboots, enable automatic start of swap:

# echo -e "/dev/sda2 none swap sw 0 0" >> /mnt/etc/fstab
# rc-update add swap

If you prefer maximum speed, you don't need configure any raid devices for swap. Just add 2 swap partitions on different disks and linux will stripe them automatically. The downside is that the moment one disk fails, the system will go down. For better reliability, put swap on RAID1.

Tip: Instead of using a separate partition for swap, zram based swap file can be used.

Encrypted swap

The below steps explains the steps to enable crypt-swap or Encrypted swap parition.

Edit the file /etc/conf.d/dmcrypt to enable crypt-swap. Ensure that source device name is correct. :

Contents of /etc/conf.d/dmcrypt

swap=crypt-swap
source='/dev/nvme0nXXX'

To use dmcrypt, start dmcrypt service and enable swap immediately:

# /etc/init.d/dmcrypt start
# swapon /dev/mapper/crypt-swap

To make the encrypted swap persistent across reboots, enable automatic start of encryption & swap:

# rc-update add dmcrypt
# rc-update add swap

To enable automatic swapon, add the relevant entry to /etc/fstab

# echo /dev/mapper/crypt-swap swap swap defaults 0 0 >> /etc/fstab

Note: The above instructions will reset/re-encrypt swap on every boot and thus no suspend to disk works with it.