What is kldloadOS

kldload is the builder and installer. kldloadOS is what you’re running afterward — an opinionated OS layer on top of CentOS, Debian, or RHEL that gives you ZFS on root, universal CLI tools, boot environments, offline package mirrors, and a consistent experience across distro families.

This page covers what kldloadOS gives you that a stock Linux install doesn’t.

Just want ZFS on root with no extras? Choose the Core profile during install. You get ZFS on root, ZFSBootMenu, and a stock distro — nothing else. See Editions.

Nothing removed, everything optional

kldloadOS does not modify, patch, replace, or remove anything from the base distro. apt, dnf, zfs, zpool, systemctl — they all work exactly as they do on a stock install. The underlying OS is completely standard.

What kldloadOS adds is a set of optional k* convenience commands that automate common tasks and provide a consistent interface across distro families. You can use them, or ignore them entirely and operate the system with native tools. Both approaches are fully supported.

One optional command set across Debian and CentOS/RHEL

Every kldload system ships the same k* CLI tools regardless of distro. If you don’t want to remember whether it’s apt or dnf, dpkg -l or rpm -qa, the k* tools abstract away the differences:

And every kpkg install, remove, and upgrade takes an automatic ZFS snapshot first. If a package breaks something, roll back in seconds.

This is significant: you can write scripts, documentation, and automation that work on both distro families with zero conditional logic. kpkg install htop tmux nginx works everywhere.

Automatic safety net for every operation

kldload tools create ZFS snapshots before destructive operations:

Plus sanoid runs automatic hourly/daily/weekly/monthly snapshots in the background.

The result: you can’t permanently break your system with a package operation. Every change is reversible.

Boot environments

Stock Linux doesn’t have boot environments. If a kernel update breaks your system, you’re in recovery mode or reinstalling.

kldload gives you ZFSBootMenu + boot environments:

kbe create before-risky-change    # checkpoint
kupgrade                          # upgrade the system
# Broken? Reboot, pick the old BE from the menu
# Or: kbe activate before-risky-change && reboot

Every upgrade, every kernel change, every DKMS rebuild — you can always go back to the last working state in one command.

ZFS on root (not bolted on)

Stock CentOS and Debian don’t support ZFS on root out of the box. Getting ZFS on root working manually requires:

1. Custom partitioning (EFI + ZFS partition)
2. Pool creation with the right properties (ashift, compression, acltype, xattr, relatime)
3. Dataset hierarchy (separate /home, /var/log, /var/cache, /srv)
4. DKMS module build for the running kernel
5. Initramfs with ZFS support
6. Bootloader that understands ZFS (ZFSBootMenu or GRUB with ZFS patches)
7. Hostid configuration (zgenhostid)
8. Proper fstab/mount ordering

kldload does all of this automatically during install. The dataset hierarchy is deterministic:

rpool
├── ROOT/default      /                (the OS)
├── home              /home            (user data, separate snapshots)
├── root              /root
├── srv               /srv             (application data)
└── var
    ├── log           /var/log         (logs, separate snapshots)
    ├── cache         /var/cache       (no auto-snapshot, cache is disposable)
    └── tmp           /var/tmp         (no auto-snapshot)

Each path is an independent ZFS dataset with its own: - Snapshot schedule - Compression settings - Quotas - Send/receive replication

Offline installation

Both RPM and APT package mirrors are baked into the ISO:

• ~900 RPMs for CentOS/RHEL installs
• ~2,700 .debs for Debian installs

No internet required. Boot from USB, pick your distro, install. This matters for: - Air-gapped environments - Unreliable network connections - Consistent, reproducible installs (same packages every time) - Fast deployment (no downloading 2GB+ of packages per machine)

Instant CoW cloning

kclone creates copy-on-write clones of any directory:

kclone /srv/production /srv/staging

The clone is instant (takes milliseconds) and starts at near-zero disk space. Only divergent blocks consume space. Use cases:

• Clone a production database for testing
• Create a staging environment from live data
• Duplicate a project directory without doubling disk usage

Multi-distro from one ISO

One ISO installs: - CentOS Stream 9 - Debian Trixie - RHEL 9 - Rocky Linux 9

The same USB stick works for all four. Same installer, same ZFS layout, same tools, same boot environments. The native package manager is still there — dnf on CentOS/RHEL, apt on Debian — fully functional. kpkg is an optional wrapper if you want one command for both.

Export to any hypervisor

kexport converts a running system to portable disk images:

kexport qcow2   # KVM / Proxmox / OpenStack
kexport vhd     # Azure / Hyper-V
kexport vmdk    # VMware ESXi / vSphere
kexport ova     # VMware / VirtualBox
kexport raw     # dd-ready image

Build one system, deploy it everywhere.

Health dashboard in one command

kst

Instantly shows pool health, disk usage, compression ratios, snapshot counts, boot environments, memory, CPU, uptime, and service status. No setup, no agents, no configuration.

What’s not changed

kldloadOS is deliberately non-invasive. The base distro is stock:

• Kernel — unmodified distro kernel. ZFS is built via DKMS, not a custom kernel.
• Package managers — apt and dnf are untouched. kpkg wraps them optionally; it does not replace, intercept, or modify them.
• Init system — stock systemd. No custom init, no wrapper services around systemd.
• Filesystem tools — zfs, zpool, zdb are standard OpenZFS. The k* tools call them underneath.
• Network stack — standard NetworkManager. WireGuard is the stock kernel module.
• No proprietary components — everything is open source (BSD 3-Clause).
• No lock-in — exports to any format, runs on any hardware. kexport uses qemu-img, not a custom tool.

If you uninstalled every k* tool, you’d have a standard CentOS or Debian system with ZFS on root. The k* tools are additions, not modifications.