Managing Storage on Flatcar Container Linux on Flatcar Container Linux

Adding disk space to your Flatcar Container Linux machine

Mon, 01 Jan 0001 00:00:00 +0000

On a Flatcar Container Linux machine, the operating system itself is mounted as a read-only partition at /usr. The root partition provides read-write storage by default and on a fresh install is mostly blank. The default size of this partition depends on the platform but it is usually between 3GB and 16GB. If more space is required simply extend the virtual machine’s disk image and Flatcar Container Linux will fix the partition table and resize the root partition to fill the disk on the next boot.

Configuring RAID on Flatcar Container Linux

Mon, 01 Jan 0001 00:00:00 +0000

Flatcar Container Linux supports composite disk devices such as RAID arrays. If the root filesystem is placed on a composite device, special care must be taken to ensure Flatcar Container Linux can find and mount the filesystem early in the boot process. GPT partition entries have a partition type GUID that specifies what type of partition it is (e.g. Linux filesystem); Flatcar Container Linux uses special type GUIDs to indicate that a partition is a component of a composite device containing the root filesystem.

Mounting storage

Mon, 01 Jan 0001 00:00:00 +0000

Butane Configs can be used to format and attach additional filesystems to Flatcar Container Linux nodes, whether such storage is provided by an underlying cloud platform, physical disk, SAN, or NAS system. This is done by specifying how partitions should be mounted in the config, and then using a systemd mount unit to mount the partition. By systemd convention , mount unit names derive from the target mount point, with interior slashes replaced by dashes, and the .mount extension appended. A unit mounting onto /var/www is thus named var-www.mount.

Configuring iSCSI on Flatcar Container Linux

Mon, 01 Jan 0001 00:00:00 +0000

iSCSI is a protocol which provides block-level access to storage devices over IP. This allows applications to treat remote storage devices as if they were local disks. iSCSI handles taking requests from clients and carrying them out on the remote SCSI devices.

Flatcar Container Linux has integrated support for mounting devices. This guide covers iSCSI configuration manually or automatically with Butane Configs .

Manual iSCSI configuration

Set the Flatcar Container Linux iSCSI initiator name

iSCSI clients each have a unique initiator name. Flatcar Container Linux generates a unique initiator name on each install and stores it in /etc/iscsi/initiatorname.iscsi. This may be replaced if necessary.

Use LVM on Flatcar Container Linux

Mon, 01 Jan 0001 00:00:00 +0000

LVM - Logical Volume Management - allows you to create logical volumes, for example to use multiple physical disks as one volume. This allows you to make the full use of all attached disks.

Flatcar Linux has built-in support for LVM. This guide covers creation of logical volumes using LVM and how to use them.

Creating LVM

There are two main ways to do this: create everything manually or use an Ignition config. We will first cover the manual way to get a better grip of what is happening, then we will cover the Ignition way.

Managing swap space Flatcar Container Linux

Mon, 01 Jan 0001 00:00:00 +0000

Swap is the process of moving pages of memory to a designated part of the hard disk, freeing up space when needed. Swap can be used to alleviate problems with low-memory environments. A modern alternative to slow swap partitions is to use RAM compression with zram.

By default Flatcar Container Linux does not include a partition for swap nor a zram configuration, however one can configure their system to have swap, either by including a dedicated partition for it, creating a swapfile, or setting up zram.

ZFS Extension for Flatcar Container Linux

Mon, 01 Jan 0001 00:00:00 +0000

The Flatcar ZFS extension was the first Flatcar extension published, introduced with Flatcar version 3913.0.0 in the Alpha channel. It provides the ZFS Linux kernel modules and the ZFS CLI tools. Support for ZFS is experimental because the ZFS kernel module lives out-of-tree which means it is not part of the upstream Linux kernel and any delay in fixing incompatibilities in the ZFS code could mean that we would have to release a Flatcar version without the ZFS extension, meaning that ZFS users won’t be able update until a follow-up Flatcar release brings ZFS support back.