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Disks

File: src/topics/disk.j. Path: /disk (DISK_PATH).

Background

RouterOS v7 manages attached storage - USB sticks, NVMe, SATA - under /disk. It matters more than it used to: container filesystems, configuration backups, downloaded files, and disk logging all land on a disk. This topic lists the devices, reports usage, formats, and ejects. Empty on routers with no storage.

Struct

jennifer
mt.Disk { id, name, model, kind, fs, sizeBytes, freeBytes, slot }

sizeBytes/freeBytes are ints (bytes); fs is "" on an unformatted disk.

name is what the lookups take. RouterOS 7 leaves its own name property empty on plain USB storage and puts the label everything else calls the disk - usb1, usb1-part1 - in slot instead, so name falls back to slot, and diskByName / formatDisk / ejectDisk match either. Whatever disks(c) prints will find the disk again.

Functions

FunctionPurpose
disks(c) → list of Diskattached storage (empty if none)
diskByName(c, name) → Diskone device
formatDisk(c, name, filesystem, label)erase + format (destructive)
ejectDisk(c, name)safe-remove a hot-pluggable disk

Examples

Inventory and free space:

jennifer
def ds as list of mt.Disk init mt.disks($c);
for (def d in $ds) {
    io.printf("%s (%s) %s: %d of %d bytes free\n",
        $d.name, $d.model, $d.fs, $d.freeBytes, $d.sizeBytes);
}

Prepare a fresh disk for containers (ext4 is the router-native choice):

jennifer
mt.formatDisk($c, "usb1", "ext4", "container-storage");

The device (usb1) and its partition (usb1-part1) are separate entries; a container root-dir lives on the partition.

Then eject before unplugging:

jennifer
mt.ejectDisk($c, "usb1");

Pitfalls

  • formatDisk erases everything, with no undo and no prompt. It is as destructive as it sounds - verify the device name against disks(c) first, and never run it on a disk with data you have not copied elsewhere. Treat it like reboot/shutdown: a deliberate, double-checked action.
  • Filesystem choice: ext4 for a router-only disk (containers, logs - POSIX permissions, robust); exfat/fat32 if you also read the disk on a PC (but no permissions, and fat32 caps files at 4 GB).
  • Flash wear: cheap USB sticks die under the constant small writes of disk logging or a busy container - use decent media, or NVMe where the board supports it.
  • name vs. slot. If a lookup ever surprises you, print the raw rows: on RouterOS 7.21.5 a USB stick reports name= (empty) and slot=usb1. This topic papers over that in both directions, but the generic verbs (mt.findByName($c, "/disk", "usb1")) filter on name server-side and will find nothing.
  • The format command was renamed. RouterOS ≤ 7.20 took /disk/format-drive; 7.21 takes /disk/format and answers the old spelling with !trap: no such command. formatDisk tries the current name and falls back to the old one, so it works on both - a direct raw.run does not.
  • Ejecting a disk in use (a running container's root-dir, active disk logging) can fail or corrupt - stop the user first.