Learn Alpine Linux - Basic Networking & Filesystem

#Introduction

Networking and the filesystem are the operational foundation of every server. Episode 7 explains how Alpine manages both the OpenRC way: network configuration in /etc/network/interfaces, the DNS resolver, the compact filesystem layout, and mount management via /etc/fstab.

Most server troubleshooting starts in these two areas — an IP that won't come up, DNS that won't resolve, or a full disk. After this episode, you'll have the tools to solve them systematically.

#Network Configuration

#/etc/network/interfaces

Alpine uses ifupdown with a format similar to Debian. The /etc/network/interfaces file defines the interfaces and how to bring them up:

auto lo
iface lo inet loopback
 
auto eth0
iface eth0 inet dhcp

The auto line marks interfaces that come up at boot, and iface eth0 inet dhcp uses DHCP. For a static IP:

auto eth0
iface eth0 inet static
    address 192.168.1.10/24
    gateway 192.168.1.1

Edit the file then apply it without rebooting:

ifup eth0
ifdown eth0

ifup eth0 and ifdown eth0 bring the interface up and down based on the definitions above.

#The ip Command and Interface Handling

For everyday network operations, use the modern ip tool:

ip addr show
ip link show
ip route show
ip addr add 192.168.1.20/24 dev eth0
ip link set eth0 up

ip link set eth0 up brings an interface up manually — equivalent to ifconfig eth0 up, but with modern syntax. Manual changes don't survive a reboot; for persistence always write them in /etc/network/interfaces.

#DNS: /etc/resolv.conf

#Configuring the Resolver

Alpine uses musl, so /etc/resolv.conf is managed directly:

nameserver 8.8.8.8
nameserver 1.1.1.1
options timeout:2 attempts:3

Each nameserver line adds a resolver. Test DNS resolution:

nslookup alpinelinux.org
getent hosts alpinelinux.org

getent hosts alpinelinux.org uses musl's getent to resolve names — using the same sources as other applications. If nslookup succeeds but an application fails, check whether resolv.conf is being read correctly.

#The Alpine Filesystem Layout

#Directory Structure

Alpine's layout follows the Filesystem Hierarchy Standard, with some quirks because it uses BusyBox and OpenRC:

/bin, /sbin      - binary inti dan applet BusyBox
/etc/apk         - konfigurasi package manager
/etc/network     - konfigurasi jaringan
/etc/init.d      - script service OpenRC
/etc/conf.d      - variabel konfigurasi service
/var/log         - log sistem
/mnt, /media     - titik mount

Because the system is small, the hierarchy isn't as dense as other distros, but all the standard directories are present. The kernel and modules live in /boot and /lib/modules.

#/etc/fstab and Mounting

#Managing Filesystems

The /etc/fstab file determines which filesystems are mounted at boot:

/dev/vda1  /      ext4  defaults,noatime 0 1
/dev/vda2  swap   swap  defaults          0 0

The format is: device, mount point, filesystem type, options, dump flag, and fsck order. Manual mount operations:

mount /dev/sdb1 /mnt/data
umount /mnt/data
df -h
blkid

df -h shows the disk usage of all mount points, while blkid shows device UUIDs — useful for writing fstab entries with UUIDs so they don't shift when disks are added.

#Filesystem Support

Alpine supports ext4, btrfs, and xfs:

apk add e2fsprogs
mkfs.ext4 /dev/sdb1
mount /dev/sdb1 /mnt/data

Install the btrfs or xfs utilities if you use those filesystems:

apk add btrfs-progs xfsprogs

apk add btrfs-progs xfsprogs provides mkfs, fsck, and maintenance tools for both filesystems.

#Basic Troubleshooting Tips

#A Quick Check Routine

When a server has issues, follow this order:

ip addr show
ip route show
getent hosts alpinelinux.org
df -h

• ip addr show confirms the interface is up and has an IP.
• ip route show confirms the default route exists.
• getent hosts confirms DNS is working.
• df -h confirms the disk isn't full.

These four commands answer the majority of connectivity and storage issues in Alpine.

#Closing

Episode 7 explained Alpine's basic networking and filesystem: the /etc/network/interfaces configuration with ifup and ifdown, the modern ip tool, the resolver in /etc/resolv.conf, the filesystem layout, /etc/fstab and mounting, and support for ext4, btrfs, and xfs.

Key takeaways:

• /etc/network/interfaces defines interfaces ifupdown-style.
• ifup and ifdown apply configuration without a reboot.
• ip addr and ip route are the main network inspection tools.
• /etc/resolv.conf determines the DNS resolver.
• /etc/fstab controls boot-time mounts with its five-column format.
• ext4, btrfs, and xfs are all supported by Alpine.

In the next episode, episode 8, we'll cover diskless, data, and USB installation modes — booting Alpine entirely from RAM with an initramfs, persisting configuration with lbu, and live system scenarios on USB media.