Name-Based VirtualHosts and SSL
As a rule, it is impossible to host more than one SSL virtual host on the same IP address and port. This is because Apache needs to know the name of the host in order to choose the correct certificate to setup the encryption layer. But the name of the host being requested is contained only in the HTTP request headers, which are part of the encrypted content. It is therefore not available until after the encryption is already negotiated. This means that the correct certificate cannot be selected, and clients will receive certificate mismatch warnings and be vulnerable to man-in-the-middle attacks.
In reality, Apache will allow you to configure name-based SSL virtual hosts, but it will always use the configuration from the first-listed virtual host (on the selected IP address and port) to setup the encryption layer. In certain specific circumstances, it is acceptable to use a single SSL configuration for several virtual hosts. In particular, this will work if the SSL certificate applies to all the virtual hosts. For example, this will work if:
All the VirtualHosts are within the same domain, eg: one.example.com and two.example.com.
You have a wildcard SSL certificate for that domain (one where the Common Name begins with an asterix: i.e *.example.com)
Renaming a Volume Group
Use the vgrename command to rename an existing volume group.
Either of the following commands renames the existing volume group vg02 to my_volume_group
# vgrename /dev/vg02 /dev/my_volume_group
or
# vgrename vg02 my_volume_group
Backing Up Volume Group Metadata
Metadata backups and archives are automatically created on every volume group and logical volume configuration change unless disabled in the lvm.conf file. By default, the metadata backup is stored in the /etc/lvm/backup file and the metadata archives are stored in the /etc/lvm/archives file.
You can manually back up the metadata to the /etc/lvm/backup file with the vgcfgbackupcommand.
The vgcfrestore command restores the metadata of a volume group from the archive to all the physical volumes in the volume groups.
Splitting a Volume Group
To split the physical volumes of a volume group and create a new volume group, use the vgsplit command.
Logical volumes cannot be split between volume groups. Each existing logical volume must be entirely on the physical volumes forming either the old or the new volume group. If necessary, however, you can use the pvmove command to force the split.
The following example splits off the new volume group vgsmall from the original volume group vgbig.
vgsplit bigvg vgsmall /dev/disk1
Volume group “vgsmall” successfully split from “vgbig”
Activating and Deactivating Volume Groups
When you create a volume group it is, by default, activated. This means that the logical volumes in that group are accessible and subject to change.
There are various circumstances for which you need to make a volume group inactive and thus unknown to the kernel. To deactivate or activate a volume group, use the -a (–available) argument of the vgchange command.
The following example deactivates the volume group my_volume_group.
# vgchange -a n my_volume_group
If clustered locking is enabled, add ’e’ to activate or deactivate a volume group exclusively on one node or ’l’ to activate or/deactivate a volume group only on the local node. Logical volumes with single-host snapshots are always activated exclusively because they can only be used on one node at once.
