ServerBuddies Support Blog

rsnapshot is a filesystem backup utility based on rsync.

Using rsnapshot, it is possible to take snapshots of your filesystems at different points in time. Using hard links, rsnapshot creates the illusion of multiple full backups, while only taking up the space of one full backup plus differences. When coupled with ssh, it is possible to take snapshots of remote filesystems as well.

rsnapshot is written in Perl, and depends on rsync. OpenSSH, GNU cp, GNU du, and the BSD logger program are also recommended, but not required.

All of these should be present on most Linux systems.

By default, the installation procedure will install all files under /usr/local. If you’ve followed these instructions so far, you will have configured rsnapshot to be installed under /usr/local, with the config file in /etc.

Under these circumstances, it will be necessary to become root to install the program. Now is the time to do so. You will, of course, need the root password to do this:

This will prompt you for the root password.

Now, to install rsnapshot, run the following command:

This will install rsnapshot with all the settings you specified in the ./configure stage. If all goes well, you will have the following files on your system:

The latest version of the program and this document can always be found at http://www.rsnapshot.org/.

More about LVM Components Physical Volumes

Physical Volumes

The underlying physical storage unit of an LVM logical volume is a block device such as a partition or whole disk. To use the device for an LVM logical volume the device must be initialized as a physical volume (PV).

Initializing a block device as a physical volume places a label near the start of the device.

By default, the LVM label is placed in the second 512-byte sector. You can overwrite this default by placing the label on any of the first 4 sectors. This allows LVM volumes to co-exist with other users of these sectors, if necessary.

An LVM label provides correct identification and device ordering for a physical device, since devices can come up in any order when the system is booted. An LVM label remains persistent across reboots and throughout a cluster.

The LVM label identifies the device as an LVM physical volume. It contains a random unique identifier (the UUID) for the physical volume. It also stores the size of the block device in bytes, and it records where the LVM metadata will be stored on the device.

The LVM metadata contains the configuration details of the LVM volume groups on your system. By default, an identical copy of the metadata is maintained in every metadata area in every physical volume within the volume group. LVM metadata is small and stored as ASCII.

Initializing Physical Volumes

Use the pvcreate command to initialize a block device to be used as a physical volume.

Initialization is analogous to formatting a file system.

The following command initializes /dev/sdd1, /dev/sde1, and /dev/sdf1 for use as LVM physical volumes.

To initialize partitions rather than whole disks: run the pvcreate command on the partition.

The following example initializes the partition /dev/hdb1 as an LVM physical volume for later use as part of an LVM logical volume.

pvcreate initializes PhysicalVolume for later use by the Logical Volume Manager (LVM). Each PhysicalVolume can be a disk partition, whole disk, meta device, or loopback file. For DOS disk partitions, the partition id should be set to 0×8e using fdisk(8), cfdisk(8), or a equivalent. For whole disk devices only the partition table must be erased, which will effectively destroy all data on that disk. This can be done by zeroing the first sector with:

Continue with vgcreate(8) to create a new volume group on PhysicalVolume, or vgextend(8) to add PhysicalVolume to an existing volume group.

Example

Initialize partition #4 on the third SCSI disk and the entire fifth SCSI disk for later use by LVM:

See Also

lvm(8), vgcreate(8), vgextend(8), lvcreate(8), cfdisk(8), fdisk(8), losetup(8), mdadd(8), vgcfgrestore(8), vgconvert(8)

Referenced By

pvchange(8), pvck(8), pvdisplay(8), pvremove(8), pvscan(8), vgchange(8), vgdisplay(8)

Troubleshooting BIND

There are a number of tools that are available to assist with testing and troubleshooting problems with your BIND configuration. The simplest tool on most systems is the host command, which simply performs an address lookup or a reverse address lookup. More complete information can be gathered using dig.

The simplest usage of host is to lookup an address, or a name.

Ask for the name servers that are authoritative for a domain by using the -t ns command line option..

The MX record can be retrieved by using the -t mx option.

Just like host, it is possible to query your default system resolver, or you can query a name server specified on the command line. For example, I could query my local name server about the nostarch.com domain.

More at http://doxfer.com/

Creating and editing ACLs

Before you can block or allow requests from some address, to some server or for some page you will need to create an appropriate ACL. The basic steps to do this are :

1. Select the type of ACL to create from the drop-down menu below the Access control lists table and click the* Create new ACL* button.

2. On the form that appears, enter a name for your new ACL in the ACL name field. If more than one has the same name, it will be treated as matched if any ACL with that name matches. The name should consist of only letters and numbers, with no spaces or special characters.

3. Fill in the rest of the form as explained in the table below.

4. In the Failure URL field, enter a complete URL that clients who are denied by this ACL will be redirected to. This allows you to define custom error pages to be displayed instead of the default Squid responses.

5. Click the Save button at the bottom of the form.

Once an ACL has been created you can edit it by clicking on its name in the list, changing the fields and clicking Save. Or your can delete it (if it is not in use by some proxy or ICP restriction) with the Delete button. As usual, the Apply Changes link must be used to activate any changes that you make.

Squid has an amazing number of ACL types, although not all are available in all versions of the server.

Many types of ACL are inappropriate for certain situations. For example, if a client sends a CONNECT request the URL path is unavailable, and thus a URL Path Regexp ACL will not work. In cases like this the ACL is automatically assumed not to match.

Article taken from - http://doxfer.com/Webmin/