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Mohit-Chachada merged 2 commits into from
Mar 18, 2026
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System Options: indicate options that are available only on Ubuntu Core #195

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System Options: indicate options that are available only on Ubuntu Core
Mohit-Chachada Mar 17, 2026
e9e237d
fix spellcheck error from main
Mohit-Chachada Mar 17, 2026
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2 changes: 1 addition & 1 deletion docs/explanation/how-snaps-work/snap-performance.md
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Expand Up @@ -225,7 +225,7 @@ The above example shows execution times related to snapd’s interface manager,

[SquashFS](https://www.kernel.org/doc/Documentation/filesystems/squashfs.txt) is a standard Linux file system that encases an operational directory structure within a single compressed file. It’s commonly used to provide bootable live Linux environments on USB storage, but it’s also used to package a snap.

A snap is a SquashFS file that contains the library and binary environment for the snap, alongside the metadata to describe its access and capabilities. The SquashFS file is either mounted by _systemd_ when the snap is first installed, or during the early phases of the bootup for a system, such as Ubuntu Core, that already has snaps installed.
A snap is a SquashFS file that contains the library and binary environment for the snap, alongside the metadata to describe its access and capabilities. The SquashFS file is either mounted by _systemd_ when the snap is first installed, or during the early phases of the boot up for a system, such as Ubuntu Core, that already has snaps installed.

SquashFS decompression occurs when a snap is first run on a system and its performance has been closely monitored. In particular, decompression performance may differ according to the compression algorithm used, the size of the SquashFS archive, the number of files it contains, whether it’s being accessed for the first time (cold-cache) or whether it’s being accessed again (warm-cache).

Expand Down
41 changes: 35 additions & 6 deletions docs/reference/administration/system-options.md
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Expand Up @@ -38,6 +38,8 @@ On a Raspberry Pi, the following options set corresponding values in the _config

Further details on the above, see the [official Raspberry Pi documentation](https://www.raspberrypi.com/documentation/computers/config_txt.html).

> ⓘ Available only on Ubuntu Core.

## system journal.persistent

Enables or disables journal persistence. Can be `true` or `false`. If persistent journals were previously enabled by this setting, changing the value to `false` will **delete all saved logs**.
Expand All @@ -47,6 +49,8 @@ Example to enable the journal:
snap set system journal.persistent=true
```

> ⓘ Available only on Ubuntu Core.

## system proxy.{http,https,ftp}

These options may be set to change the proxies to be used by the system when communicating with external sites that speak the respective protocols:
Expand All @@ -56,6 +60,8 @@ snap set system proxy.http="http://<proxy_addr>:<proxy_port>"
snap set system proxy.https="http://<proxy_addr>:<proxy_port>"
```

> ⓘ Available only on Ubuntu Core.

## system refresh

There are four system-wide options that are used to manage how updates are handed:
Expand Down Expand Up @@ -83,8 +89,7 @@ snap set system homedirs=<destination-directory>

See {ref}`Home directories outside of ‘/home’ <interfaces-home-outside-home>` for further details.

Available since snapd 2.59.

> ⓘ Available since snapd _2.59_.

## system resilience.vitality-hint

Expand Down Expand Up @@ -114,6 +119,8 @@ snap set system service.console-conf.disable=true

This option is defined in the {ref}`gadget snap <reference-development-yaml-schemas-the-gadget-snap>` and cannot be changed at runtime.

> ⓘ Available only on Ubuntu Core.

## system service.ssh.disable

Can be set to _true_ to disable the SSH service at startup.
Expand All @@ -122,6 +129,8 @@ Can be set to _true_ to disable the SSH service at startup.
snap set system service.ssh.disable=true
```

> ⓘ Available only on Ubuntu Core.

## system service.ssh.listen-address

Specifies the local address that the SSH daemon should listen on.
Expand All @@ -136,7 +145,7 @@ snap set system service.ssh.listen-address=myhost
snap set system service.ssh.listen-address=192.168.1.2,myhost,foo:8022
```

Available since snapd _2.59_, and only on Ubuntu Core 20 or later.
> ⓘ Available since snapd _2.59_ and only on Ubuntu Core 20 or later.

## system snapshots.automatic.retention

Expand All @@ -153,7 +162,7 @@ snap set system snapshots.automatic.retention=no

> ⓘ Disabling automatic snapshots will *not* affect preexisting, automatically generated snapshots, but only those generated by subsequent snap removals.

Automatic snapshots require snap version _2.39+_.
> ⓘ Automatic snapshots require snap version _2.39+_.

## system store.access

Expand All @@ -171,7 +180,7 @@ Unsetting the parameter restores the default access to the store.
snap unset system store.access
```

Available since snapd 2.61
> ⓘ Available since snapd _2.61_ and only on Ubuntu Core.

## system store-certs

Expand Down Expand Up @@ -208,6 +217,8 @@ defaults:
size: 200M
```

> ⓘ Available only on Ubuntu Core.

## system system.disable-backlight-service

May be set to _true_ to disable the backlight service:
Expand All @@ -216,6 +227,8 @@ May be set to _true_ to disable the backlight service:
snap set core system.disable-backlight-service=true
```

> ⓘ Available only on Ubuntu Core.

## system system.kernel.cmdline-append

Dynamically add permitted kernel boot parameters to the default kernel command line on devices using the GRUB bootloader and with [Ubuntu Core 20/22](https://ubuntu.com/core/docs/uc20/inside) or later.
Expand Down Expand Up @@ -258,6 +271,8 @@ $ cat /etc/sysctl.d/99-snapd.conf
kernel.printk = 1 4 1 7
```

> ⓘ Available only on Ubuntu Core.

## system system.motd

Ubuntu Core systems come with a default message of the day. From Ubuntu Core 24 onwards, the message of the day can be customized from the defaults configuration section in the {ref}`gadget.yaml <reference-development-yaml-schemas-the-gadget-snap>` file to set a custom message available since first boot:
Expand Down Expand Up @@ -291,6 +306,8 @@ The custom message can be removed with _unset_ which will reset to the default m
snap unset system system.motd
```

> ⓘ Available only on Ubuntu Core.

## system system.network.netplan

On systems that support [Netplan](https://netplan.io/), such as Ubuntu Core 20 and 22, snapd can both query and configure the Netplan key and value notation through its _get_ and _set_ system options commands:
Expand Down Expand Up @@ -348,7 +365,7 @@ snap set system system.network.netplan.network.ethernets.enp0s2.gateway4=10.0.2.

See [Netplan reference](https://netplan.io/reference) for details on the key and value pairs used for network configuration.

Available since snapd 2.55.4
> ⓘ Available since snapd _2.55.4_ and only on Ubuntu Core.

## system system.power-key-action

Expand All @@ -372,6 +389,8 @@ To set the system power button behaviour to _hibernate_, for example, enter the
snap set system system.power-key-action=hibernate
```

> ⓘ Available only on Ubuntu Core.

## system system.timezone

May be used to set a time zone value, as typically found in `/usr/share/zoneinfo`, such as `America/Chicago`.
Expand Down Expand Up @@ -402,6 +421,8 @@ $ snap get -d system
}
```

> ⓘ Available only on Ubuntu Core.

## system tmp.size

Configures the default size for the `/tmp` mount point on Ubuntu Core devices:
Expand Down Expand Up @@ -431,6 +452,8 @@ snap unset system tmp.size
```
By default, `/tmp` is set to use 50% of physical RAM.

> ⓘ Available only on Ubuntu Core.

## system users.create.automatic

When _true_, permits the system to create users automatically from a valid [system-user assertion](https://ubuntu.com/core/docs/reference/assertions/system-user), such as an assertion stored on external storage (see [System user](https://ubuntu.com/core/docs/system-user) for more details). When _false_, users can only created manually with _create user_ API calls:
Expand All @@ -447,6 +470,8 @@ When set to `True`, Ubuntu Core user accounts will be locked for 900 seconds aft

Can be either `True` or `False`.

> ⓘ Available only on Ubuntu Core.

## system watchdog.runtime-timeout

Configures the system's hardware watchdog _runtime_ timeout.
Expand All @@ -466,6 +491,8 @@ snap set system watchdog.runtime-timeout=1m
The Raspberry Pi hardware watchdog timer is limited to a maximum timeout of 15 seconds.
```

> ⓘ Available only on Ubuntu Core.

## system watchdog.shutdown-timeout

Configures the system's hardware watchdog _shutdown_ timeout.
Expand All @@ -482,3 +509,5 @@ The following example will set the timeout to 500 seconds:
snap set system watchdog.shutdown-timeout=500
```

> ⓘ Available only on Ubuntu Core.

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