Tyler Chris - Fedora Linux стр 74.

sh-3.1# umount /home

sh-3.1# fsck -f /dev/main/home

e2fsck 1.38 (30-Jun-2005)

Pass 1: Checking inodes, blocks, and sizes

Pass 2: Checking directory structure

Pass 3: Checking directory connectivity

Pass 4: Checking reference counts

Pass 5: Checking group summary information

/dev/main/home: 121/256000 files (2.5% non-contiguous), 12704/262144 blocks

sh-3.1# resize2fs /dev/main/home900M

resize2fs 1.38 (30-Jun-2005)

Resizing the filesystem on /dev/main/home to 230400 (4k) blocks.

The filesystem on /dev/main/home is now 229376 blocks long.

sh-3.1# lvreduce /dev/main/home --size 950M

Rounding up size to full physical extent 952.00 MB

WARNING: Reducing active logical volume to 952.00 MB

THIS MAY DESTROY YOUR DATA (filesystem etc.)

Do you really want to reduce home? [y/n]: y

Reducing logical volume home to 952.00 MB

Logical volume home successfully resized

sh-3.1# resize2fs/dev/main/home

resize2fs 1.38 (30-Jun-2005)

Resizing the filesystem on /dev/main/home to 243712 (4k) blocks.

The filesystem on /dev/main/home is now 243712 blocks long.

The warning message displayed by lvreduce is accurate: if you set the logical volume size smaller than the filesystem size, you will lose data! Be extremely careful when resizing volumes; it's a good idea to back up your data first.

If your system has the default Volume Group and Logical Volume names, substitute the correct name (such as /dev/VolGroup00/LogVol00 ) for /dev/main/home . The problem is that it's hard to keep the logical volume names straightwhich is why I recommend using more meaningful names.

When you're done, type reboot

or press Ctrl-Alt-Delete to restart the system.

6.1.1.5. Managing LVM in rescue mode

After prompting you for the language ( Figure 1-5 ) and keyboard type ( Figure 1-6 ) the same way it does for a network installation (use the arrow keys and Enter to select the correct value for each), the system will ask if you wish to start the network interfaces, as shown in Figure 6-6 . Select No by pressing Tab and then Enter.

Figure 6-6. Rescue mode network interface dialog

The next screen, shown in Figure 6-7 , enables you to select filesystem mounting; select Skip by pressing Tab twice and then pressing Enter.

Figure 6-7. Rescue mode filesystem mounting dialog

You will then be presented with a shell prompt ( sh-3.1# ). The LVM device nodes will not be present until you scan for them and activate them:

sh-3.1# lvm vgscan

Reading all physical volumes. This may take a while...

Found volume group "main" using metadata type lvm2

sh-3.1# lvm vgchange -ay

3 logical volume(s) in volume group "main" now active

The LVM device nodes will be created in /dev/mapper/<vg-lv> and /dev/<vg>/<lv> . The /dev/dm-<N> nodes are not created.

sh-3.1# fsck -f/dev/main/root

WARNING: couldn't open /etc/fstab: No such file or directory

e2fsck 1.38 (30-Jun-2005)

Pass 1: Checking inodes, blocks, and sizes

Pass 2: Checking directory structure

Pass 3: Checking directory connectivity

Pass 4: Checking reference counts

Pass 5: Checking group summary information

/dev/main/root: 134009/1532576 files (0.5% non-contiguous), 793321/1531904 blocks

sh-3.1# resize2fs/dev/main/root 5600M

resize2fs 1.38 (30-Jun-2005)

Resizing the filesystem on /dev/main/root to 1433600 (4k) blocks.

The filesystem on /dev/main/root is now 1433600 blocks long.

sh-3.1# lvreduce/dev/main/root--size5650M

Rounding up size to full physical extent 5.53 GB

WARNING: Reducing active logical volume to 5.53 GB

THIS MAY DESTROY YOUR DATA (filesystem etc.)

Do you really want to reduce root? [y/n]: y

Reducing logical volume root to 5.53 GB

Logical volume root successfully resized

sh-3.1# resize2fs/dev/main/root

resize2fs 1.38 (30-Jun-2005)

Resizing the filesystem on /dev/main/root to 1449984 (4k) blocks.

The filesystem on /dev/main/root is now 1449984 blocks long.

Type exit or press Ctrl-D to exit from the rescue-mode shell. The system will then reboot; don't forget to remove the installation media.

6.1.2. How Does It Work?

Obviously, each LE exists as a PE somewhere in the LVM system. A kernel facility called the device mapper converts between LE and PE extent numbers. When the physical extents are changedas the result of a pvmove , for examplethe logical extent numbers remain the same, providing continuity for the filesystem.

Extents tend to be fairly largeanywhere from

8 KB to 16 GB in size, but typically in the 1 to 128 MB range (32 MB is the default extent size used during installation). Larger extent sizes cause a reduction in the LVM overhead because the extent tables are smaller and need to be consulted less often. However, LVs and PVs must be a multiple of the extent size, so a large size limits granularity. The extent size can be configured when the VG is created, either at boot time or by using the --physicalextentsize argument to vgcreate .

A large, efficient extent size is usually too big for effective copy-on-write operation during snapshots, so a smaller chunk size is used for copy-on-write management. This can be configured using the --chunksize option to lvcreate .