winnielinnie
MVP
- Joined
- Oct 22, 2019
- Messages
- 3,641
And wonderful people deserve to know about the wonderful, lesser-known tricks of ZFS. 
(My clickbait game is strong. No one does it better than me. Your criticisms of my superficial methods only make me stronger.)
Organize and label your snapshots with helpful notes!
This is possible thanks to a useful, yet often overlooked feature called "User Properties". As long as you follow the base:name format, you can tag any snapshot with a custom property. I use this to mark important milestones or notes on particular snapshots like so:
Some real-world examples would be to "mark" certain milestones or reminders.
Milestones can be used to "bookend" a sequential batch of snapshots that you don't want to destroy today, but have confirmed that they are low priority and nothing depends on them. These can be the "first to go" in situations where you need to quickly reclaim space on your pool.
You could do something like this:
If you need to reclaim a bunch of space on your pool, you'll know that you can issue a batch deletion between the aforementioned snapshots above.
For a quick review of all snapshots with custom notes, you can use
You can also narrow it down to only a specific pool or dataset, without searching recursively:
You will see output that appears like this:
The other real-world example could be used to mark certain reminders, such as searching through snapshots for a deleted file that you believe existed in January 2021. Maybe you don't remember the filename, but have an idea of where to look.
So you do this:
Then as you confidently finish thoroughly checking each one, you can update the note:
And thus, your "report" will look something like this:
Final thoughts and caveats.
Keep in mind that these "User Properties" (i.e, "custom notes") are always visible. Not even ZFS encryption will hide them. Try to avoid using sensitive or identifiable words. (Perhaps use "coded" language or abbreviations that only you will understand?)
To "remove" a note outright, you need to "inherit" the "User Property". This will essentially "inherit" the dataset's property (which doesn't exist), and thus the snapshot will no longer have this property either.
For the reason above, it's best practice to avoid setting custom notes on datasets. Only use them for snapshots. Otherwise, every snapshot by default will "inherit" the custom note. And if you try to "remove" a note from a snapshot, it will simply re-inherit the dataset's note.
Sadly, you cannot add "User Properties" (and hence "notes") to bookmarks. I'm not really sure why. Perhaps it's a worthwhile feature request for the OpenZFS GitHub?
(My clickbait game is strong. No one does it better than me. Your criticisms of my superficial methods only make me stronger.)
Organize and label your snapshots with helpful notes!
This is possible thanks to a useful, yet often overlooked feature called "User Properties". As long as you follow the base:name format, you can tag any snapshot with a custom property. I use this to mark important milestones or notes on particular snapshots like so:
Code:
zfs set custom:note="Write your note here" mypool/dataset@snapshot
Some real-world examples would be to "mark" certain milestones or reminders.
Milestones can be used to "bookend" a sequential batch of snapshots that you don't want to destroy today, but have confirmed that they are low priority and nothing depends on them. These can be the "first to go" in situations where you need to quickly reclaim space on your pool.
You could do something like this:
Code:
zfs set custom:note="Safe to destroy from here until 2022-06-01 to save space" tank/downloads@manual_2020-01-31 zfs set custom:note="Safe to destroy from 2020-01-31 until here to save space" tank/downloads@manual_2022-06-01
If you need to reclaim a bunch of space on your pool, you'll know that you can issue a batch deletion between the aforementioned snapshots above.
For a quick review of all snapshots with custom notes, you can use
zfs get to list them:Code:
zfs get -t snap -r -s local custom:note
You can also narrow it down to only a specific pool or dataset, without searching recursively:
Code:
zfs get -t snap -s local custom:note tank/downloads
You will see output that appears like this:
Code:
tank/downloads@manual_2020-01-31 custom:note Safe to destroy from here until 2022-06-01 to save space local tank/downloads@manual_2022-06-01 custom:note Safe to destroy from 2020-01-31 until here to save space local
The other real-world example could be used to mark certain reminders, such as searching through snapshots for a deleted file that you believe existed in January 2021. Maybe you don't remember the filename, but have an idea of where to look.
So you do this:
Code:
zfs set custom:note="DID NOT CHECK HERE YET" tank/archives@auto_2021-01-01 zfs set custom:note="DID NOT CHECK HERE YET" tank/archives@auto_2021-01-07 zfs set custom:note="DID NOT CHECK HERE YET" tank/archives@auto_2021-01-14 zfs set custom:note="DID NOT CHECK HERE YET" tank/archives@auto_2021-01-21 zfs set custom:note="DID NOT CHECK HERE YET" tank/archives@auto_2021-01-28
Then as you confidently finish thoroughly checking each one, you can update the note:
Code:
zfs set custom:note="Nothing found" tank/archives@auto_2021-01-01 zfs set custom:note="Nothing found" tank/archives@auto_2021-01-07
And thus, your "report" will look something like this:
Code:
zfs get -t snap -s local custom:note tank/archives tank/archives@auto_2021-01-01 custom:note Nothing found local tank/archives@auto_2021-01-07 custom:note Nothing found local tank/archives@auto_2021-01-14 custom:note DID NOT CHECK HERE YET local tank/archives@auto_2021-01-21 custom:note DID NOT CHECK HERE YET local tank/archives@auto_2021-01-28 custom:note DID NOT CHECK HERE YET local
Final thoughts and caveats.
Keep in mind that these "User Properties" (i.e, "custom notes") are always visible. Not even ZFS encryption will hide them. Try to avoid using sensitive or identifiable words. (Perhaps use "coded" language or abbreviations that only you will understand?)
To "remove" a note outright, you need to "inherit" the "User Property". This will essentially "inherit" the dataset's property (which doesn't exist), and thus the snapshot will no longer have this property either.
Code:
zfs inherit custom:note tank/archives@auto_2021-01-01
For the reason above, it's best practice to avoid setting custom notes on datasets. Only use them for snapshots. Otherwise, every snapshot by default will "inherit" the custom note. And if you try to "remove" a note from a snapshot, it will simply re-inherit the dataset's note.
Sadly, you cannot add "User Properties" (and hence "notes") to bookmarks. I'm not really sure why. Perhaps it's a worthwhile feature request for the OpenZFS GitHub?
Last edited:
