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Difference between revisions of "Btrfs"
Subvolume
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If you do use more then one device, please also read the section about RAID. You are able to add/remove devices at any time to increase/decrease the size of the volume. With adding/removing devices it is also possible to move a volume from one device to another (without changing the UUID). | If you do use more then one device, please also read the section about RAID. You are able to add/remove devices at any time to increase/decrease the size of the volume. With adding/removing devices it is also possible to move a volume from one device to another (without changing the UUID). | ||
Usually you do not mount the Btrfs volume itself, but you mount subvolumes. There may be times when it is practical to mount the Btrfs volume itself. Then you are able to change the volume layout. All (writeable) subvolumes inside a volume are movable inside the volume with mv. Moving subvolumes will not touch the data, but change the volume layout in an instant. | Usually you do not mount the Btrfs volume itself, but you mount subvolumes. There may be times when it is practical to mount the Btrfs volume-root itself. Then you are able to change the volume layout. All (writeable) subvolumes inside a volume are movable inside the volume with mv. Moving subvolumes will not touch the data, but change the volume layout in an instant. | ||
When not otherwise specified, additional devices are handled as '''J'''ust a '''B'''unch '''o'''f '''D'''isks (JBOD) | When not otherwise specified, additional devices are handled as '''J'''ust a '''B'''unch '''o'''f '''D'''isks (JBOD) | ||
{{BoxInfo|Tip|In most cases it is advisable to use '''only one volume'''}} | {{BoxInfo|Tip|In most cases it is advisable to use '''only one volume'''}} | ||
=== move a volume to another disk === | === move a volume to another disk === | ||
There are a lot of ways you can move a "normal" filesystem from one disk to another. But there are dangers with moving btrfs volumes that do not exist with other filesystems! '''Don´t ever move a btrfs volume with a tool that does not say it is 100% btrfs-proof.''' | There are a lot of ways you can move a "normal" filesystem from one disk to another. But there are dangers with moving btrfs volumes that do not exist with other filesystems! '''Don´t ever move a btrfs volume with a tool that does not say it is 100% btrfs-proof.''' | ||
When at any time there are 2 partitions in one computer that have the same filesystem UUID, one ore both filesystems '''may be destroyed'''. Under the topic '''tips''' you will find an easy way to do | When at any time there are 2 partitions in one computer that have the same filesystem UUID, one ore both filesystems '''may be destroyed'''. Under the topic '''tips''' you will find an easy way to do move a volume without any danger | ||
{{BoxDanger|Do NOT| | {{BoxDanger|Do NOT| | ||
* make a block-level copy of a Btrfs filesystem to another block device | * make a block-level copy of a Btrfs filesystem to another block device | ||
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== subvolume == | == subvolume == | ||
A Btrfs subvolume is an independently mountable POSIX file-tree and '''not a block device'''. It is the part of a volume that will be '''mounted writeable''' into your Linux system. By convention the names of subvolumes start with '''@ (@, @home, @snapshots''' ...). | |||
All subvolumes share the space of the Btrfs volume. You may create subvolumes at will. (You may think of subvolumes as sort of "dynamic partitions" inside a Btrfs volume) | |||
== snapshot == | == snapshot == | ||