Storage mangment API: disks infos

[christophehenry]

The problem

Rel: YunoHost/issues#1823.
Add API for getting infos on hard drives.

[christophehenry]

Ok I think this is a good first step. Here is an exemple of the result this produces:

{
    "sda": {
        "devname": "/dev/sda",
        "model": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
        "serial": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
        "size": xxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
        "links": [
            "/dev/disk/by-diskseq/1",
            "/dev/disk/by-id/ata-xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
            "/dev/disk/by-id/wwn-xxxxxxxxxxxxxxxxxxxxxxxx",
            "/dev/disk/by-path/pci-0000:01:00.1-ata-1",
            "/dev/disk/by-path/pci-0000:01:00.1-ata-1.0"
        ],
        "partitions": {
            "sda1": {
                "devname": "/dev/sda",
                "filesystem": "btrfs",
                "encrypted": true,
                "mountpoint": "/home"
            }
        }
    },
    "sdb": {
        "devname": "/dev/sdb",
        "model": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
        "serial": "xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
        "size": xxxxxxxxxxxxxxxxxxxxxxxxxxxxx,
        "links": [
            "/dev/disk/by-diskseq/2",
            "/dev/disk/by-id/ata-xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
            "/dev/disk/by-id/wwn-xxxxxxxxxxxxxxxxxxxxxxxxxxxxx",
            "/dev/disk/by-path/pci-0000:0a:00.0-ata-6",
            "/dev/disk/by-path/pci-0000:0a:00.0-ata-6.0"
        ],
        "partitions": {
            "sdb1": {
                "devname": "/dev/sdb",
                "filesystem": "vfat",
                "encrypted": false,
                "mountpoint": "/boot/efi"
            },
            "sdb2": {
                "devname": "/dev/sdb",
                "filesystem": "ext4",
                "encrypted": false,
                "mountpoint": "/boot"
            },
            "sdb3": {
                "devname": "/dev/sdb",
                "filesystem": "btrfs",
                "encrypted": true,
                "mountpoint": "/"
            }
        }
    }
}

In a future PR, I'd like to add the device type (HDD, SSD, …) and RPM for HDDs. I don't really know how to do that. TrueNAS does it by using its own library. In the meantime, this is ready for review.

[christophehenry]

A few notes here: I rewrote this PR to use the udisks2 API which provides much more details about disks and is easier to use that udev + other sources of infos.

But as a pure dbus API, the code is less self-explanatory. It's mainly about parsing dictionary.

Maybe I can make use of something like dbus-fast, IDK.

Tell me if it's OK to add the udisk daemon to Ynh. I'm not aware of everything it entails.

[alexAubin]

Naively udisk sounds fine to me 👍

[zamentur]

Yes i think udisk is a good idea, also because it could help to automount external usb or disk...

[zamentur]

In a future PR, I'd like to add the device type (HDD, SSD, …) and RPM for HDDs. I don't really know how to do that. TrueNAS does it by using its own library. In the meantime, this is ready for review.

You can know if it's a HDD or SSD by checking directly the info inside /sys...

cat /sys/block/sda/queue/rotational

0 -> SSD
1 -> HDD

/sys/block/sda/queue/removable to know if it's an usb removable disk i guess

We could also imagine check for ssd how many written is made, in order to compute an end of life percentage.

[christophehenry]

You can know if it's a HDD or SSD by checking directly the info inside /sys...

udisks2 provides the information so I don't need a solution anymore. Thanks.

[christophehenry]

Does someone knows a more efficient way to interact with dbus than just list all the objects managed by Udisks2 here?

[christophehenry]

Should it be file-scoped? I don't know how it is efficient to create a bus at each call.

[zamentur]

I guess you could use this kind of info:

/sys/block/sda/size -> Size in Byte
/sys/block/sda/removable -> USB or not
/sys/block/sda/queue/rotational -> HDD or not
/sys/block/sda/ro -> read only mode
/sys/block/sda/stat -> https://www.kernel.org/doc/Documentation/ABI/testing/sysfs-block
/sys/block/sda/sdaX -> partition name and info

[zamentur]

but maybe dbus is ok... (i am not a dbus expert)

[christophehenry]

I don't believe it is useful to test this. We'd basically be testing the udisks2 library which is never a good idea.