swap

Wrappers around Linux swap tooling:

• mkswap — initialize a swap area
• swapon — enable swap
• swapoff — disable swap

This module constructs ward.process.cmd(...) invocations; it does not parse output. consumers can use wardlib.tools.out (or their own parsing) on the :output() result.

Most swap operations require elevated privileges. Prefer using wardlib.tools.with with the sudo/doas middleware.

Import

local Swap = require("wardlib.app.swap").Swap

API

Swap.mkswap(target, opts)

Builds: mkswap <opts...> <target>

Swap.swapon(targets, opts)

Builds: swapon <opts...> [targets...]

• If targets is nil, runs swapon with only modeled options (useful for --show).
• If targets is a string array, all targets are appended.

Swap.swapoff(targets, opts)

Builds: swapoff <opts...> [targets...]

• If targets is nil, runs swapoff with only modeled options (useful for -a).

Swap.status(opts)

Convenience: swapon --show.

Swap.disable_all(opts)

Convenience: swapoff -a.

Options

MkswapOpts

• label: string? — -L <label>
• uuid: string? — -U <uuid>
• pagesize: number? — --pagesize <size>
• force: boolean? — -f
• check: boolean? — -c (check bad blocks)
• extra: string[]? — extra argv appended after modeled options

SwaponOpts

• all: boolean? — -a
• discard: string? — --discard[=<policy>]
  • pass "" (empty string) to emit bare --discard
• fixpgsz: boolean? — --fixpgsz
• priority: number? — -p <prio>

Formatting for --show:

• show: boolean? — --show
• noheadings: boolean? — --noheadings
• raw: boolean? — --raw
• bytes: boolean? — --bytes
• output: string|string[]? — --output <cols> (array is joined by ,)

Escape hatch:

• extra: string[]? — extra argv appended after modeled options

SwapoffOpts

• all: boolean? — -a
• verbose: boolean? — -v
• extra: string[]? — extra argv appended after modeled options

Examples

Create swap on a file (mkswap + swapon)

This example shows the command construction only. File allocation (fallocate/dd) is handled elsewhere.

local Swap = require("wardlib.app.swap").Swap
local w = require("wardlib.tools.with")

w.with(w.middleware.sudo(), function()
  -- mkswap -f -L swap0 /swapfile
  Swap.mkswap("/swapfile", { force = true, label = "swap0" }):run()

  -- swapon /swapfile
  Swap.swapon("/swapfile"):run()
end)

Disable a specific swap and remove it from service

local Swap = require("wardlib.app.swap").Swap
local w = require("wardlib.tools.with")

w.with(w.middleware.sudo(), function()
  -- swapoff /swapfile
  Swap.swapoff("/swapfile"):run()
end)

Show active swaps

local Swap = require("wardlib.app.swap").Swap

-- swapon --show --noheadings --output NAME,SIZE,USED,PRIO
local cmd = Swap.status({
  noheadings = true,
  output = { "NAME", "SIZE", "USED", "PRIO" },
})

-- cmd:output().stdout contains the table. Use wardlib.tools.out if you need parsing.

Enable all swaps from /etc/fstab

local Swap = require("wardlib.app.swap").Swap
local w = require("wardlib.tools.with")

w.with(w.middleware.sudo(), Swap.swapon(nil, { all = true }))
  :run()

Disable all swaps

local Swap = require("wardlib.app.swap").Swap
local w = require("wardlib.tools.with")

w.with(w.middleware.sudo(), Swap.disable_all())
  :run()