OverlayFS - Revision history

Macmpi: /* Immutable root with tmpfs overlay */ rephrase tip

2025-10-13T09:48:40Z

Immutable root with tmpfs overlay: rephrase tip

← Older revision		Revision as of 09:48, 13 October 2025
Line 60:		Line 60:
	root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms.		root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms.

	{{Tip\| By default rootfs is allocated 50% of available RAM (without swap): this may be temporarily adjusted to arbitrary value (like <code>300MB</code>) at runtime by issuing <code>mount -o remount,size{{=}}300M /</code>. ~~Optional~~ flags ~~(like <code>size{{=}}</code>) to set allocated RAM for rootfs~~ may ~~also~~ be added as ~~comma-separated list within~~ <code>overlaytmpfsflags{{=}}~~</code> parameter (defaults are: <code>mode~~{{=}}~~0755,rw~~</code>). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).}}		{{Tip\| By default rootfs is allocated 50% of available RAM (without swap): this may be temporarily adjusted to arbitrary value (like <code>300MB</code>) at runtime by issuing <code>mount -o remount,size{{=}}300M /</code>. For permanent change, optional kernel parameters flags may be added as <code>overlaytmpfsflags{{=}}size{{=}}300M</code>. [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).}}

Macmpi: tmpfs allocation as tip

2025-09-25T16:02:49Z

tmpfs allocation as tip

← Older revision		Revision as of 16:02, 25 September 2025
Line 60:		Line 60:
	root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms.		root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms.

	By default rootfs is allocated 50% of available RAM (without swap): this may be temporarily adjusted to arbitrary value (like ''300MB'') at runtime by issuing <code>mount -o remount,size=300M /</code>. Optional flags (like <code>size=</code> to set allocated RAM for rootfs) may also be added as comma-separated list within ~~{{ic\|~~overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).		{{Tip\| By default rootfs is allocated 50% of available RAM (without swap): this may be temporarily adjusted to arbitrary value (like <code>300MB</code>) at runtime by issuing <code>mount -o remount,size{{=}}300M /</code>. Optional flags (like <code>size{{=}}</code>) to set allocated RAM for rootfs may also be added as comma-separated list within <code>overlaytmpfsflags{{=}}</code> parameter (defaults are: <code>mode{{=}}0755,rw</code>). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).}}

Macmpi: /* Immutable root with tmpfs overlay */ clarify allocated RAM options

2025-04-20T06:19:42Z

Immutable root with tmpfs overlay: clarify allocated RAM options

← Older revision		Revision as of 06:19, 20 April 2025
Line 58:		Line 58:
	{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}		{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}

	root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms. Optional flags (like size= to ~~limit~~ allocated RAM) may also be added as comma-separated list in {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).		root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms.

			By default rootfs is allocated 50% of available RAM (without swap): this may be temporarily adjusted to arbitrary value (like ''300MB'') at runtime by issuing <code>mount -o remount,size=300M /</code>. Optional flags (like <code>size=</code> to set allocated RAM for rootfs) may also be added as comma-separated list within {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).

Macmpi at 14:37, 4 April 2025

2025-04-04T14:37:46Z

← Older revision		Revision as of 14:37, 4 April 2025
Line 9:		Line 9:
	This may be accomplished by overlaying disk-backed loopback filesystem into RAM-based diskless filesystem.		This may be accomplished by overlaying disk-backed loopback filesystem into RAM-based diskless filesystem.

	{{Note\| '''such construct is a diversion from standard diskless mode''' and may compromise some of this mode core-benefits (potentially slower since disk access is involved, disk/SD wear if such loopback storage is made rw, etc...): user might want to reconsider (better) relevance of other supported install modes (disk, data).}}		{{Note\| '''such construct is a diversion from standard diskless mode''' and may compromise some of this mode core-benefits (potentially slower since disk access is involved, disk/SD wear if such loopback storage is made rw, etc...): user might want to reconsider (better) relevance of other supported install modes (system disk, data disk).}}

	The example below illustrates a usecase on Pi (add extra packages that may not fit in RAM, with a loop-back disk-image), but can be derived for different purposes, on different platforms.		The example below illustrates a usecase on Pi (add extra packages that may not fit in RAM, with a loop-back disk-image), but can be derived for different purposes, on different platforms.

Macmpi: /* Immutable root with tmpfs overlay */ wordsmithing

2025-04-02T11:31:40Z

Immutable root with tmpfs overlay: wordsmithing

← Older revision		Revision as of 11:31, 2 April 2025
Line 54:		Line 54:
	Alpine initramfs features an option to run '''system disk install''' with ''tmpfs'' overlay on root filesystem: root filesystem is then mounted read-only (original system install is run unmodified across reboots), with all runtime files to be updated in RAM only (hence discarded at shutdown).		Alpine initramfs features an option to run '''system disk install''' with ''tmpfs'' overlay on root filesystem: root filesystem is then mounted read-only (original system install is run unmodified across reboots), with all runtime files to be updated in RAM only (hence discarded at shutdown).

	This option can provide an interesting alternative scenario to ''diskless'' install on systems with very limited RAM (full system is run from disk rather than copied into RAM), and prevents rw stress on ~~disk/SD~~ (dynamic files are stored in RAM).		This option can provide an interesting alternative scenario to ''diskless'' install on systems with very limited RAM (full system is run from disk rather than copied into RAM), and prevents rw I/O stress & wear on media (dynamic files are stored in RAM).

	{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}		{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}

Macmpi: /* Loopback image with overlayfs */ typo

2025-04-02T11:17:50Z

Loopback image with overlayfs: typo

← Older revision		Revision as of 11:17, 2 April 2025
Line 9:		Line 9:
	This may be accomplished by overlaying disk-backed loopback filesystem into RAM-based diskless filesystem.		This may be accomplished by overlaying disk-backed loopback filesystem into RAM-based diskless filesystem.

	{{Note\| '''such construct is a diversion from standard diskless mode''' and may compromise some of this mode core-benefits (potentially slower since disk access is involved, disk/SD ~~swear~~ if such loopback storage is made rw, etc...): user might want to reconsider (better) relevance of other supported install modes (disk, data).}}		{{Note\| '''such construct is a diversion from standard diskless mode''' and may compromise some of this mode core-benefits (potentially slower since disk access is involved, disk/SD wear if such loopback storage is made rw, etc...): user might want to reconsider (better) relevance of other supported install modes (disk, data).}}

	The example below illustrates a usecase on Pi (add extra packages that may not fit in RAM, with a loop-back disk-image), but can be derived for different purposes, on different platforms.		The example below illustrates a usecase on Pi (add extra packages that may not fit in RAM, with a loop-back disk-image), but can be derived for different purposes, on different platforms.

Macmpi: /* Immutable root with tmpfs overlay */

2025-04-02T11:11:25Z

Immutable root with tmpfs overlay

← Older revision		Revision as of 11:11, 2 April 2025
Line 84:		Line 84:
	Removing and adding back the <code>overlaytmpfs=yes</code> option in the {{path\|/boot/cmdline.txt}} file using a toggle script will allow easy maintenance on the pi and any software/configuration can be easily added/removed.		Removing and adding back the <code>overlaytmpfs=yes</code> option in the {{path\|/boot/cmdline.txt}} file using a toggle script will allow easy maintenance on the pi and any software/configuration can be easily added/removed.

	Another [[Immutable root with atomic upgrades]] configuration is also possible.		Another [[Immutable root with atomic upgrades]] advanced configuration is also possible.

	== See also ==		== See also ==

Macmpi: /* Root filesystem tmpfs overlay */ use immutable root naming

2025-04-02T10:58:47Z

Root filesystem tmpfs overlay: use immutable root naming

← Older revision		Revision as of 10:58, 2 April 2025
Line 50:		Line 50:
	If it is something a bit bigger, then you can use <code>apk add</code> but then not commit it. It will be persistent (in <code>/usr</code>), but be sure to check everything you need is in that directory and not in folders you have not made persistent.		If it is something a bit bigger, then you can use <code>apk add</code> but then not commit it. It will be persistent (in <code>/usr</code>), but be sure to check everything you need is in that directory and not in folders you have not made persistent.

	== ~~Root filesystem~~ tmpfs overlay ==		== Immutable root with tmpfs overlay ==

	Alpine initramfs features an option to run '''system disk install''' with ''tmpfs'' overlay on root filesystem: root filesystem is then mounted read-only (original system install is run unmodified across reboots), with all runtime files to be updated in RAM only (hence discarded at shutdown).		Alpine initramfs features an option to run '''system disk install''' with ''tmpfs'' overlay on root filesystem: root filesystem is then mounted read-only (original system install is run unmodified across reboots), with all runtime files to be updated in RAM only (hence discarded at shutdown).
Line 83:		Line 83:

	Removing and adding back the <code>overlaytmpfs=yes</code> option in the {{path\|/boot/cmdline.txt}} file using a toggle script will allow easy maintenance on the pi and any software/configuration can be easily added/removed.		Removing and adding back the <code>overlaytmpfs=yes</code> option in the {{path\|/boot/cmdline.txt}} file using a toggle script will allow easy maintenance on the pi and any software/configuration can be easily added/removed.

			Another [[Immutable root with atomic upgrades]] configuration is also possible.

	== See also ==		== See also ==

Macmpi: /* Root filesystem tmpfs overlay */

2025-04-02T10:45:16Z

Root filesystem tmpfs overlay

← Older revision		Revision as of 10:45, 2 April 2025
Line 56:		Line 56:
	This option can provide an interesting alternative scenario to ''diskless'' install on systems with very limited RAM (full system is run from disk rather than copied into RAM), and prevents rw stress on disk/SD (dynamic files are stored in RAM).		This option can provide an interesting alternative scenario to ''diskless'' install on systems with very limited RAM (full system is run from disk rather than copied into RAM), and prevents rw stress on disk/SD (dynamic files are stored in RAM).

	{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}		{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}

	root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms. Optional flags (like size= to limit allocated RAM) may also be added as comma-separated list in {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).		root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms. Optional flags (like size= to limit allocated RAM) may also be added as comma-separated list in {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).

Macmpi: /* Root filesystem tmpfs overlay */ add reference for dockerd limitation

2025-04-02T10:43:05Z

Root filesystem tmpfs overlay: add reference for dockerd limitation

← Older revision		Revision as of 10:43, 2 April 2025
Line 56:		Line 56:
	This option can provide an interesting alternative scenario to ''diskless'' install on systems with very limited RAM (full system is run from disk rather than copied into RAM), and prevents rw stress on disk/SD (dynamic files are stored in RAM).		This option can provide an interesting alternative scenario to ''diskless'' install on systems with very limited RAM (full system is run from disk rather than copied into RAM), and prevents rw stress on disk/SD (dynamic files are stored in RAM).

	{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option (incompatibility with docker's default ''overlay2'' storage driver: ''vfs'' storage driver may be an option but with potential performance impacts).}}		{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}

	root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms. Optional flags (like size= to limit allocated RAM) may also be added as comma-separated list in {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).		root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms. Optional flags (like size= to limit allocated RAM) may also be added as comma-separated list in {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).

← Older revision		Revision as of 06:19, 20 April 2025
Line 58:		Line 58:
	{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}		{{Note\| this option may come with some runtime limitations. For instance ''dockerd'' will not run without specific configuration under this option ([https://docs.docker.com/engine/storage/drivers/select-storage-driver/#supported-backing-filesystems incompatibility with docker's default ''overlay2'' storage driver]: ''vfs'' storage driver may be an option but with potential performance impacts).}}

	root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms. Optional flags (like size= to ~~limit~~ allocated RAM) may also be added as comma-separated list in {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).		root filesystem tmpfs overlay mode can be enabled by adding the {{ic\|overlaytmpfs{{=}}yes}} option to the Kernel command-line parameters, on '''system disk install''' configuration, on any platforms.

			By default rootfs is allocated 50% of available RAM (without swap): this may be temporarily adjusted to arbitrary value (like ''300MB'') at runtime by issuing <code>mount -o remount,size=300M /</code>. Optional flags (like <code>size=</code> to set allocated RAM for rootfs) may also be added as comma-separated list within {{ic\|overlaytmpfsflags{{=}}}} parameter (defaults are: mode=0755,rw). [https://gitlab.alpinelinux.org/alpine/mkinitfs/-/blob/b63297a201c96ded7a43192be93c2d3438e19e73/initramfs-init.in#L728 More info here]).