Class: LVM::LogicalVolume

Inherits:
Object
  • Object
show all
Defined in:
lib/lvm/logical_volume.rb

Overview

This class represents an LVM logical volume, in all its glory. You can perform various operations on it.

Instance Method Summary collapse

Constructor Details

#initialize(path_or_vg_name, lv_name = nil) ⇒ LogicalVolume

Create a new instance of LVM::LogicalVolume.

New instances can be created in one of two ways:

* Pass a single argument, containing any path which LVM can resolve to
  a logical volume.  Typically, this will either be `/dev/<vg>/<lv>`
  or `/dev/mapper/<vg>-<lv>`, but we don't try to parse it ourselves,
  relying instead on `lvs` to do the heavy lifting.

* Pass two arguments, which are the volume group name and logical
  volume name, respectively.

This method will raise ‘RuntimeError` if the path specified can’t be resolved to an LV, or if the specified VG name or LV name don’t resolve to an active logical volume.



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# File 'lib/lvm/logical_volume.rb', line 22

def initialize(path_or_vg_name, lv_name=nil)
  if lv_name.nil?
    path = path_or_vg_name
    @vg_name, @lv_name = `lvs --noheadings -o vg_name,lv_name #{path} 2>/dev/null`.strip.split(/\s+/, 2)
    if $?.exitstatus != 0
      raise RuntimeError,
            "Failed to interrogate LVM about '#{path}'.  Perhaps you misspelt it?"
    end
  else
    @vg_name = path_or_vg_name
    @lv_name = lv_name
  end

  @vgcfg = LVM::VGConfig.new(@vg_name)
  @lvcfg = @vgcfg.logical_volumes[@lv_name]

  if @lvcfg.nil?
    raise RuntimeError,
          "Logical volume #{@lv_name} does not exist in volume group #{@vg_name}"
  end
end

Instance Method Details

#changes ⇒ Object

Return an array of ranges, each of which represents an inclusive range of bytes which are different between this logical volume and its origin.

If this LV is not a snapshot, this method returns an empty array.



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# File 'lib/lvm/logical_volume.rb', line 74

def changes
  return [] unless snapshot?

  if @lvcfg.thin?
    LVM::ThinSnapshot.new(@vg_name, @lv_name)
  else
    LVM::Snapshot.new(@vg_name, @lv_name)
  end.differences
end

#origin ⇒ Object

Return an LVM::LogicalVolume object which is the origin volume of this one (if this LV is a snapshot), or ‘nil` otherwise.



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# File 'lib/lvm/logical_volume.rb', line 57

def origin
  return nil unless snapshot?

  if @lvcfg.origin
    LVM::LogicalVolume.new(@vg_name, @lvcfg.origin)
  else
    origin_lv_name = @vgcfg.logical_volumes.values.find { |lv| lv.cow_store == @lv_name }.origin
    LVM::LogicalVolume.new(@vg_name, origin_lv_name)
  end
end

#path ⇒ Object

Return a string containing a canonical path to the block device representing this LV.



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# File 'lib/lvm/logical_volume.rb', line 46

def path
  "/dev/mapper/#{@vg_name.gsub('-', '--')}-#{@lv_name.gsub('-', '--')}"
end

#snapshot? ⇒ Boolean

Is this LV a snapshot?

Returns:

  • (Boolean) 


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# File 'lib/lvm/logical_volume.rb', line 51

def snapshot?
  @lvcfg.snapshot?
end