The initial display shows the physical (red) and logical (blue) views of the last volume group listed. If you click on a logical volume in the Logical View, the corresponding areas in the physical view are highlighted, as shown in Figure 6-2 .
Figure 6-2. Viewing the location of LV data within PVs
6.1.1.1.1. Growing a logical volume
Figure 6-3. LVM properties dialog
Change the unit control from Extents to Gigabytes or Megabytes so that the LV size is displayed in meaningful units; then click on the horizontal slider and drag it to the desired size (or type the size into the "LV size" field or click "Use Remaining").
Click OK. The LV will be resized, then the filesystem will be resized, and then the LVM information will be reloaded to update the display. On most systems, this will take just a few seconds.
If the resize fails with the message "No space left on device," you may have attempted to resize the filesystem past the maximum that can be done while the filesystem is mounted (in use). You can attempt to unmount the filesystem by deselecting the checkbox labeled Mount and then retry the operation (this will always fail for the root filesystem and will usually fail for filesystems containing /var and /home , in which case you may need to use single-user mode).
6.1.1.2. Shrinking a logical volume
The catch is that logical volumes containing ext3 filesystems can be reduced in size only when they are unmounted, so you
will be asked if the filesystem may be unmounted during the resize operation. Click Yes.
Whenever the system is booted normally, the root ( / ) and /var filesystems will be in use, so you will not be able to unmount them, and therefore the resize will fail. You'll need to use a special procedure (detailed shortly) to shrink those filesystems.
The /home filesystem is a different story; if you log in as root instead of using a normal user account, the /home filesystem will not be in use, and you can successfully shrink /home . If any non- root users have logged in since the system was booted, they may have left processes running, such as the esound daemon (esd). These can be terminated with the fuser command:
# fuser -k /home/*
/home/chris: 13464c
The output shows that the directory /home/chris was in use as the current directory ( c ) of process 13464 . That process is killed, as specified by the -k option. Once this has been done, you can resize the /home directory.
6.1.1.2.1. Creating a new logical volume
Select the volume group's Logical View element in the lefthand panel, then click Create New Logical Volume at the bottom of the center panel. The dialog shown in Figure 6-4 will appear.
Figure 6-4. Create New Logical Volume dialog
Enter an LV name consisting of letters, digits, and underscores. Change the LV size unit from Extents to Gigabytes (or Megabytes) and enter the desired LV size directly or by using the slider (click the "Use remaining" button to use all of the free space in the PV).
To create a filesystem in this LV, change the Filesystem type control (near the bottom of the dialog) from None to ext3, and select the checkboxes for Mount and "Mount when rebooted." In the "Mount point" field, type the name of the directory where you wish the new filesystem to appear.
For example, to create a 10 GB partition for music and video files, you could enter an LV name of multimedia , set the size to 10 GB, and create an ext3 filesystem with a mount point of /media .
Click OK. The LV and filesystem will be created and mounted, and you can start using the filesystem immediately.
6.1.1.2.2. Creating a snapshot
snapshotSnapshots enable you to make a self-consistent backup of a filesystem to media such as tape. If you don't use snapshots and you back up an active filesystem containing a database to tape, the database tables would get copied at different times; if the database contained e-commerce data, perhaps the customer table would get copied before the order table. If an order was received from a new customer while the backup was in progress, it is possible that the order table on the tape will include the order but the customer table may not include the new customer. This could lead to severe problems when trying to use the data at a later time. On the other hand, if you take a snapshot and then back that up, the various files will all be in the same state on tape.
In addition, snapshots are useful for self-administered document recovery: if you take a snapshot of your users' files each night and make that snapshot available to them, they can recover from their own mistakes if they mess up a spreadsheet or delete an important document. For example, if you take a snapshot of /home and make it available as /yesterday/home , the deleted document /home/jamie/budget.ods can be recovered as /yesterday/home/jamie/budget.ods .
Snapshots are also used to test software or procedures without affecting live data. For example, if you take a snapshot of the logical volume containing the /home filesystem, and then unmount the original filesystem and mount the snapshot in its place, you can