escli commands- How to get ESXi version information?

~ # esxcli system version get
Product: VMware ESXi
Version: 5.5.0
Build: Releasebuild-1623387
Update: 1
How to get the uuid?
~ # esxcli system uuid get
53bf0f5e-5b22-8964-2574-000c29f89b93
How to get the hostname ? 
~ # esxcli system hostname get
Domain Name: ganesh.com
Fully Qualified Domain Name: esx1.ganesh.com
Host Name: esx1
How to check the Load on server ? we can also use “uptime” for same 
~ # esxcli system process stats load get
Load1Minute: 0.02
Load15Minutes: 0.03
Load5Minutes: 0.02
How Many processes are running on ESXi ?
~ # esxcli system process stats running get
Running Processes: 405
How to get the boot device information for ESXi?
~ # esxcli system boot device get
Boot Filesystem UUID: 5bba5c75-aadf80d0-d554-c0ac58729550
Boot NIC:
Stateless Boot NIC:
How to see the coredump device used to capture dump ?
~ # esxcli system coredump file list
Path Active Configured Size
——————————————————————————————————- —— ———- ———
/vmfs/volumes/53c033b3-b6a7b6f3-e8bf-000c29f89b93/vmkdump/564D3C1B-1B4F-DD7B-61A7-737834F89B93.dumpfile true true 119537664
How to see the coredump partition information ?
~ # esxcli system coredump partition list
Name Path Active Configured
————————————————————————– ———————————————————————————————- —— ———-
t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:7 /vmfs/devices/disks/t10.ATA_____VMware_Virtual_IDE_Hard_Drive___________00000000000000000001:7 true true
How to list the loaded module? Partial output is shown.
~ # esxcli system module list
Name Is Loaded Is Enabled
—————————– ——— ———-
vmkernel true true
chardevs true true
user true true
vmkapi_socket true true
procfs true true
procMisc true true
How to see the information related to particular Module ?
~ # esxcli system module get -m swapobj
Module: swapobj
Module File: /usr/lib/vmware/vmkmod/swapobj
License: VMware
Version:
Signed Status: VMware Signed
Signature Issuer: VMware, Inc.
Signature Digest: 7308 1040 f1ab 8d96 07c0 0a51 eef7 3fd4 a836 01a1 0341 fc15 21bd 97da ce61 6073
Signature FingerPrint: cb44 247a 1614 cea1 2079 362d ec86 9d0e
Provided Namespaces: com.vmware.swapobj@0
Required Namespaces: com.vmware.vmkapi@v2_2_0_0, com.vmware.vmkapi.incompat@v2_2_0_0, com.vmware.vmklinkmpi@0, com.vmware.vsanPrivate@0.0.0.1
How to see the log rotation policies ?
~ # esxcli system syslog config get
Default Network Retry Timeout: 180
Local Log Output: /scratch/log
Local Log Output Is Configured: false
Local Log Output Is Persistent: true
Local Logging Default Rotation Size: 1024
Local Logging Default Rotations: 8
Log To Unique Subdirectory: false
Remote Host: <none>
How to see special purpose file systems?
~ # esxcli system visorfs ramdisk list
Ramdisk Name System Include in Coredumps Reserved Maximum Used Peak Used Free Reserved Free Maximum Inodes Allocated Inodes Used Inodes Mount Point
———— —— ——————– ——— ———- ——– ——— —- ————- ————– —————- ———– —————————
root true true 32768 KiB 32768 KiB 460 KiB 468 KiB 98 % 98 % 8192 4096 3559 /
etc true true 28672 KiB 28672 KiB 180 KiB 212 KiB 99 % 99 % 4096 1024 463 /etc
tmp false false 2048 KiB 196608 KiB 8 KiB 232 KiB 99 % 99 % 8192 256 4 /tmp
hostdstats false false 0 KiB 84992 KiB 1784 KiB 1784 KiB 97 % 0 % 8192 32 4 /var/lib/vmware/hostd/stats

******************************************HARDWARE*****************************************

How to list the CPU information related to ESXi?
~ # esxcli hardware cpu global get
CPU Packages: 1
CPU Cores: 2
CPU Threads: 2
Hyperthreading Active: false
Hyperthreading Supported: false
Hyperthreading Enabled: true
HV Support: 3
HV Replay Capable: false
HV Replay Disabled Reasons: incompatible CPU
How to list the details information related to each core ?
~ # esxcli hardware cpu list
CPU:0
Id: 0
Package Id: 0
Family: 6
Model: 60
Type: 0
Stepping: 3
Brand: GenuineIntel
Core Speed: 3400060000
Bus Speed: 66000000
APIC ID: 0x0
Node: 0
L2 Cache Size: 262144
L2 Cache Associativity: 8
L2 Cache Line Size: 64
L2 Cache CPU Count: 2
L3 Cache Size: 8388608
L3 Cache Associativity: 16
L3 Cache Line Size: 64
L3 Cache CPU Count: 2
CPU:1
Id: 1
Package Id: 0
Family: 6
Model: 60
Type: 0
Stepping: 3
Brand: GenuineIntel
Core Speed: 3400060000
Bus Speed: 66000000
APIC ID: 0x1
Node: 0
L2 Cache Size: 262144
L2 Cache Associativity: 8
L2 Cache Line Size: 64
L2 Cache CPU Count: 2
L3 Cache Size: 8388608
L3 Cache Associativity: 16
L3 Cache Line Size: 64
L3 Cache CPU Count: 2
How to check the physical memory present ?
~ # esxcli hardware memory get
Physical Memory: 4294430720 Bytes
Reliable Memory: 0 Bytes
NUMA Node Count: 1
How to Check the Hardware Clock ?
~ # esxcli hardware clock get
2014-07-15T18:30:34Z
How to list PCI devices connected ?
~ # esxcli hardware pci list | more
000:000:00.0
Address: 000:000:00.0
Segment: 0x0000
Bus: 0x00
Slot: 0x00
Most useful command to check the serial number of physical server and other related information to HW.
~ # smbiosDump.



Other ESXi commands:

/bin # esxcfg-route -n
Neighbor         MAC Address        Interface      Expiry   
192.168.7.214    a8:bb:cf:13:59:1e  vmk0           19m51s   
/bin # esxcfg-route -l
VMkernel Routes:
Network          Netmask          Gateway          Interface     
192.168.0.0      255.255.255.0    Local Subnet     vmk1          
192.168.7.0      255.255.255.0    Local Subnet     vmk0          
default          0.0.0.0          192.168.7.1      vmk0          
/bin #


/bin # esxcli system boot device get
   Boot Filesystem UUID: 1556b475-c56fdaca-1854-36a080fccc0f
   Boot NIC:
   Stateless Boot NIC:
/bin # esxcli system uuid get

5809ac37-315e-7491-ed45-000c294b413e
/bin #
/bin # esxcli system coredump file list
Error: Unknown command or namespace system coredump file list

/bin # esxcli hardware memory get
   Physical Memory: 4294430720 Bytes
   NUMA Node Count: 1
/bin #
/bin # esxcli system uuid get
5809ac37-315e-7491-ed45-000c294b413e


/bin # esxcli system version get
   Product: VMware ESXi
   Version: 5.1.0
   Build: Releasebuild-1065491
   Update: 1
/bin # vmware -l
VMware ESXi 5.1.0 Update 1
/bin # vmware -v
VMware ESXi 5.1.0 build-1065491


/bin # esxcli system boot device get
   Boot Filesystem UUID: 1556b475-c56fdaca-1854-36a080fccc0f
   Boot NIC:
   Stateless Boot NIC:
/bin # esxcli system uuid get
5809ac37-315e-7491-ed45-000c294b413e

About the ESXi 5.x and 6.x firewall

Purpose

This article provides information about the Firewall feature introduced in VMware vSphere ESXi 5.0 and later, which provides a new access control capability for ESXi.

Resolution

These are important points about the ESXi 5.x firewall:

• ESXi 5.0 has a new firewall engine that is not based on iptables.
• The firewall is enabled by default and allows Internet Control Message Protocol (ICMP) pings and communication with DHCP and DNS (UDP only) clients.
• The UI for configuring the firewall on ESXi 5.x and 6.x is similar to that used to configure the ESX firewall.
• The firewall is service oriented.
• You have the ability to restrict access to specific services based on IP address/Subnet Mask.
• There is Host Profile support for the ESXi 5.x and 6.x firewall.
• If you upgrade from ESX to ESXi 5.x, firewall settings are preserved.

A new esxcli interface named esxcfg-firewall is available in ESXi 5.x. This table summarizes the commands available in this interface:

 

Command	Description
esxcli network firewall get	Returns the enabled or disabled status of the firewall and lists default actions.
esxcli network firewall set --default-action	Update default actions.
esxcli network firewall set --enabled	Set to true to enable the firewall, set to false to disable the firewall.
esxcli network firewall load	Load the firewall module and rule set configuration files.
esxcli network firewall refresh	Refresh the firewall configuration by reading the rule set files if the firewall module is loaded.
esxcli network firewall unload	Destroy filters and unload the firewall module.
esxcli network firewall ruleset list	List rule sets information.
esxcli network firewall ruleset set --allowedall	Set the allowedall flag.
esxcli network firewall ruleset set --enabled	Enable or disable the specified rule set.
esxcli network firewall ruleset allowedip list	List the allowed IP addresses of the specified rule set.
esxcli network firewall ruleset allowedip add	Allow access to the rule set from the specified IP address or range of IP addresses.
esxcli network firewall ruleset allowedip remove	Remove access to the rule set from the specified IP address or range of IP addresses.

For example:

To enable the sshClient firewall ruleset:

esxcli network firewall ruleset set --enabled false --ruleset-id=sshClient

Additional Information

For more information about the ESXi 5.0 firewall, see the vSphere Security Guide.

The firewall remains loaded, even when disabled. For example:

Firewall enabled:

# esxcli network firewall set --enabled true

# esxcli network firewall get

Default Action: DROP

Enabled: true

Loaded: true

Firewall disabled:

# esxcli network firewall set --enabled false

# esxcli network firewall get

Default Action: DROP

Enabled: false

Loaded: true

How to dynamically change the runlevel of Linux system without rebooting

The current run level of the system can be changed dynamically without the necessity to reboot the system. This can be achieved using the telinit command with the required runlevel as the command line argument.
For example you can switch into single user mode by running the following command:
    telinit S
The administrator could subsequently return to full multi-user, X graphical interface mode either by entering:
    telinit 5

If you have made changes to the /etc/inittab file to change the default runlevel and want to change the system to that new default you can do so by using the telinit with the q command-line option:
    telinit q

It is important to note that telinit can only be run as root and even then only from the system console.

What is the ext3 filesystem and journaling?

The ext3 filesystem, developed by RedHat extends the popular ext2 filesystem with the introduction of journaling.

What is a Journaling Filesystem?

A journaling filesystem keeps a journal or log of the changes that are being made to the filesystem during disk writing that can be used to rapidly reconstruct corruptions that may occur due to events such a system crash or power outage. The level of journaling performed by the file system can be configured to provide a number of levels of logging depending on your needs and performance requirements.

What are the Advantages of a Journaling Filesystem?

There are a number of advantages to using a journaling files system.

Both the size and volume of data stored on disk drives has grown exponentially over the years. The probelm with a non-journaled file system is that following a crash the fsck (filesystem consistency check) utility has to be run. fsck will scan the entire filesystem validating all entries and making sure that blocks are allocated and referenced correctly. If it finds a corrupt entry it will attempt to fix the problem. The issues here are two-fold. Firstly, the fsck utility will not always be able to repair damage and you will end up with  data in the lost+found directory. This is data that was being used by an application but the system no longer knows where they were reference from. The other problem is the issue of time. It can take a very long time to complete the fsck process on a large file system leading to unacceptable down time.

A journaled file system records information in a log area on a disk (the journal and log do not need to be on the same device) during each write. This is a essentially an "intent to commit" data to the filesystem. The amount of information logged is configurable and ranges from not logging anything, to logging what is known as the "metadata" (i.e ownership, date stamp information etc), to logging the "metadata" and the data blocks that are to be written to the file. Once the log is updated the system then writes the actual data to the appropriate areas of the filesystem and marks an entry in the log to say the data is committed.

After a crash the filesystem can very quickly be brought back on-line using the journal log reducing what could take minutes using fsck to seconds with the added advantage that there is considerably less chance of data loss or corruption.

What is a Journal Checkpoint?
When a file is accessed on the filesystem, the last snapshot of that file is read from the disk into memory. The journal log is then consulted to see if any uncommitted changes have been made to the file since the data was last written to the file (essentially looking for an "intention to commit" in the log entry as described above). At particular points the filesystem will update file data on the disk from the uncommited log entries and trim those entries from the log. Committing operations from the log and synchronizing the log and its associated filesystem is called a checkpoint.
What are the disadvantages of a Journaled Filesystem?

Nothing in life is is free and ext3 and journaled filesystems are no exception to the rule. The biggest draw back of journaling is in the area of performance simply because more disk writes are required to store information in the log. In practice, however, unless you are running system where disk performance is absolutely critical the performance difference will be negligable.

What Journaling Options are Available with the ext3 filesystem?

The ext3 filesystem provides three options. These are as follows:

• writeback - greater speed at the price of limited data integrity. Allows old data to show up in files after a crash and relies on kernel's standard writebacks to flush buffers.
  
  
• ordered -  that the data is consistent with the file system; recently-written files will never show up with garbage contents after a crash at the cost of some speed.
  
  
• journal - Journals all data requiring greater journal space and reduced performance. The most secure data retention policy.

Does the Journal log have to be on the same disk as the filesystem?

No, the ext3 journal log does not have to be on the same physical device as the filesystem it is logging. On a RedHat Linux the journal device can be specified using the journal_device= option with the -journal-options command line argument of the tune2fs utility.

Collecting diagnostic information for VMware ESX/ESXi (653)

Details

Note: If you are directed to this article through a VMware Fusion support request, see Collecting diagnostic information for VMware Fusion (1003894).

VMware Technical Support routinely requests the diagnostic information from you when a support request is addressed. This diagnostic information contains product specific logs and configuration files from the host on which the product is run. This information is gathered using a specific script or tool within the product.

This article provides procedures for obtaining diagnostic information for an VMware ESX/ESXi host using the vSphere or VI Client. For other methods of collecting the same information, see Collecting diagnostic information for VMware ESX/ESXi using the vm-support command (1010705) and Collecting diagnostic information for VMware vCenter Server and ESX/ESXi using the vSphere PowerCLI (1027932).

The diagnostic information obtained by using this article is uploaded to VMware Technical Support. To uniquely identify your information, use the Support Request (SR) number you receive when you create the new SR.

• For information on opening a support request, see How to File a Support Request.
  
• For information on uploading your support files, see Uploading diagnostic information for VMware (1008525).
  
• For information on obtaining diagnostic information for other VMware products, see Collecting diagnostic information for VMware products (1008524).

Solution

Diagnostic information can be obtained from VMware ESX/ESXi hosts using the vSphere or VI Client. The user interface differs between versions, use the instructions appropriate for your version:

• Obtaining Diagnostic Information for ESXi 5.x and 6.0 hosts using the vSphere Client
• Obtaining Diagnostic Information for ESXi 5.x and 6.0 hosts using the vSphere Web Client
• Obtaining Diagnostic Information for ESX/ESXi 4.x hosts using the vSphere Client
• Obtaining Diagnostic Information for ESX/ESXi 2.x and 3.x hosts using the Virtual Infrastructure Client

Obtaining Diagnostic Information for ESXi 5.x and 6.0 hosts using the vSphere Client

ESXi 5.x host diagnostic information can be gathered using the vSphere Client connected to the ESXi host or to vCenter Server.
To gather diagnostic data using the VMware vSphere Client:

1. Open the vSphere Client and connect to vCenter Server or directly to an ESXi 5.x host.
2. Log in using an account with administrative privileges or with the Global.Diagnostics permission.
3. Select an ESXi host, cluster, or datacenter in the inventory.
4. Click the File > Export > Export System Logs.
5. If a group of ESXi hosts are available in the selected context, select the host or group of hosts from the Source list.
6. Click Next.
7. In the System Logs pane, select the components for which the diagnostic information must be obtained. To collect diagnostic information for all the components, click Select All.
   
   Note: Confirm that HungVM is not selected as this may cause a virtual machine failure.
   
8. If required, select the Gather performance data option and specify a duration and interval.
   
   
   
9. Click Next.
10. In the Download Location pane, click Browse and select a location on the client's disk where you have to save the support bundle.
11. Click Next.
12. In the Ready to Complete pane, review the summary and click Finish. The Downloading System Logs Bundles dialog appears and provides progress status for the creation and downloading of the support bundle from each source. A Generate system logs bundles task is created.
13. When complete, upload the logs to the SFTP/FTP site. For more information, see Uploading diagnostic information for VMware (1008525)
    
    

Obtaining Diagnostic Information for ESXi 5.x and 6.0 hosts using the vSphere Web Client  

ESXi 5.x host diagnostic information can be gathered using the vSphere Web Client connected to the ESXi host or to vCenter Server.
To gather diagnostic data using the VMware vSphere Web Client:

1. Open the vSphere Web Client.
2. Log in using an account with administrative privileges or with the Global.Diagnostics permission.
3. Select Hosts and Clusters from the Home tab.
4. Select an ESXi host, or vCenter in the inventory.
5. Click Actions.
6. Select All vCenter Actions > Export System Logs...
7. If a group of ESXi hosts are available in the selected context, select the host or group of hosts from the Source list.
8. Click Next.
9. In the System Logs pane, select the components for which the diagnostic information must be obtained. To collect diagnostic information for all the components, click Select All.
10. If required, select the Gather performance data option and specify a duration and interval.
11. Click Generate Log Bundle.
12. Click Download Log Bundle.
13. Upload the logs to the SFTP/FTP site. For more information, see Uploading diagnostic information for VMware (1008525)

Obtaining Diagnostic Information for ESX/ESXi 4.x hosts using the vSphere Client

ESX/ESXi 4.x host diagnostic information can be gathered using the vSphere Client connected to the ESX/ESXi host or vCenter Server.
To gather diagnostic data using the VMware vSphere Client:

1. Open the vSphere Client and connect to vCenter Server or directly to an ESXi 4.x host.
2. Log in with an administrative user or other account with the Global.Diagnostics permission.
3. Click the File menu, and select Export, Export System Logs.
4. In the Export System Logs dialog, select the host or group of hosts to collect diagnostic information from.
   
   Notes:
   
   • The list of hosts is not displayed when the vSphere Client is directly connected to an ESX/ESXi host.
   • Selecting Include information from vCenter Server and vSphere Client includes logs from vCenter Server and the Client in the same export.
   
   
   
5. Specify a location on the client's disk to save the support bundle. Click the Browse button and select a directory. Click OK.
   
6. A Generate system logs task is created. When complete, the logs will be downloaded by the client. At this stage, it is common to receive a Certificate Security Warning similar to:
   
   
   
   Optionally, view the certificate and install it to prevent future warnings. Click Ignore to download the log bundle.
   
7. The log bundle(s) from the selected host(s) appear in the specified directory. When complete, upload the logs to the SFTP/FTP site. For more information, see Uploading diagnostic information to VMware (1008525).
   

Obtaining Diagnostic Information For ESX 2.x and 3.x hosts using the Virtual Infrastructure Client

ESX/ESXi 3.x and ESX 2.x host diagnostic information can be gathered using the VMware Virtual Infrastructure (VI) Client connected to the ESX/ESXi host or to the VirtualCenter Server.
To gather diagnostic data using the VMware VI Client:

1. Open the VI Client and connect to VirtualCenter Server or directly to an ESX/ESXi host.
2. Log in with an administrative user or other account with the Global.Diagnostics permission.
3. Click the File menu, and select Export, Export Diagnostic Datas.
4. In the Save Diagnostic Data dialog, select the host or group of hosts to collect diagnostic information from.
   
   Note:
   
   • The list of hosts is not displayed when the VI Client is directly connected to an ESX/ESXi host.
   • Selecting Include information from VirtualCenter Server includes logs from vCenter Server in the same export.
   
   
   
5. Specify a location on the client's disk to save the support bundle. Click the Browse button and select a directory. Click OK.
   
6. A Generate System Logs task is created. When complete, the logs will be downloaded by the client. At this stage, it is common to receive a Certificate Problem Warning similar to:
   
   
   
   Optionally, select to ignore certificate errors. Click Ignore to download the log bundle.
   
7. The log bundle(s) from the selected host(s) appear in the specified directory. When complete, upload the logs to the SFTP/FTP site. For more information, see
    Uploading diagnostic information to VMware (1008525).

SqlServerWriter missing when VSSadmin list writers command is run.

1. we run Vssadmin list writers command and sqlserverwriter is missing and
2. Also, there is no error message in Application event logs and
3. Also, SQLserver VSS writer service is running
Here are the steps you need to follow to resolve such issues.
1. First of all we need to check if there are any spaces in the databases names. please run the query :
select ‘#’ + name +’#’  from sys.databases 
if you notice any space in database names e.g. #test  # , we need to make sure we remove the space from the database name.
Please follow this article to rename the database name : – http://msdn.microsoft.com/en-us/library/ms345378.aspx
once you remove the space in the database name, then issue vssadmin list writers command and check if the SQLwriter is there or not
2. If still SQLwriter is not there then:
please check the service logon which is mostly Nt authority/system or any user which you have mentioned as service logon, is added in SQL server as sysadmin privileges or not. If it’s not there then please make it as syadmin. Run the VSSadmin list writers command.

Why do we need backup and types of backup

Most of the people want to know about the backups because one of the other day you will definitely need backup of your data.There are many different types of backups and here i try to cover some of them.If something is missing or something need to be added to this article you can post your suggestions.

Why do you need backup?
Backups are needed in case a file or a group of files is lost. The reasons for losing files include
Hardware failure like disk breaking,accidentally deleting wrong file and computer being stolen.
Backups help in all the above situations. In addition, it may be good to have access to older versions of files, for example a configuration file worked a week ago, but since then it has been changed and nobody remembers how, its just not working anymore.
There are other solutions, and they are good to have if you can afford them. These include
redundant disks (RAID 1 or 5), so that one disk can break without loss of data,using an undelete system (or not making mistakes when deleting files locking up computers.
These help, but if there is anything you do not want to lose on the computer, make sure there are backups and they can be restored.
What to backup?
If there is room on the backup media, and time limits permit running backups long enough, it probably is wisest to back up everything. You may skip /tmp or other places where it is known there are only temporary files that nobody wants to backup.
If space or time limits place restrictions, consider not backing up the following
Files that come directly from a CD or other removable media. It may even be faster to copy them again from CD than restoring from backup media.
Files that can be regenerated easily. For example, object files that can be made with make. Just make sure all the source files and compilers are backed up.
If the Internet connection is fast, it may be easy enough to download files again. Just keep a list of the files and where to download them from.
Backup devices and media
You need some media to store the backups. It is preferable to use removable media, to store the backups away from the computer and to get "unlimited" storage for backups.
If the backups are on-line, they can be wiped out by mistake. If the backups are on the same disk as the original data, they do not help at all if the disk fails and is not readable anymore. If the backup media is cheap, it is possible to take a backup every day and store them indefinitely.
Floppy,Disk,Tapes,CD-R and CD-RW are the medias available for backup
Planning a Backup
Before doing a backup, plan it carefully. Consider
Which files are irreplaceable without a back up. Irreplaceable files probably include those in users' home directories (including /root), and configuration files, such as those in the /etc/ directory.
Which files are on removable drives, such as cd s or floppies. Since you probably do not need to back up removable drives, you might unmount them before doing a complete system backup.
Which files can be easily replaced by installing a package or doing a selective install or upgrade of the operating system. You can save time and storage space by not including these files in a backup.
Which files are unnecessary or dangerous to backup. For example, files in /tmp are probably unnecessary, while restoring some files that are in the /proc directory could crash the system.
Whether to compress files using gzip or bzip2 . Compressing saves space, but adds another step to the backup. Also, while compression is generally reliable, it creates another stage at which the process can fail.
Whether users are responsible for backing up their own files. Since only the root user has full permissions for all files on the system, usually backups are best done by the root user. However, if users back up their own files, you might omit backing up the home directory, or at least not back it up regularly.
Choosing a Backup Tool
Linux has several tools for backing up and restoring files
dump / restore : Old tools that work with filesystems, rather than files, and can back up unmounted devices. Although you can easyly control what is backed up with dump by editing a single column in the /etc/fstab file, for some reason these utilities have fallen into disuse. Today, many distributions of Linux, including Debian, do not even include them by default. If you want to use dump and restore , you must install them yourself.
tar : A standard backup tool, and by far the easiest to use. It is especially useful for backing up over multiple removable devices using the -M option.
cpio : A very flexible command, but one that is hard to use because of the unusual way in which the command must be entered.
dd : The dd command is one of the original Unix utilities and should be in everyone's tool box. It can strip headers, extract parts of binary files and write into the middle of floppy disks; it is used by the Linux kernel Makefiles to make boot images.
Mondo : Mondo is reliable. It backs up your GNU/Linux server or workstation to tape, CD-R, CD-RW, DVD-R[W], DVD+R[W], NFS or hard disk partition. In the event of catastrophic data loss, you will be able to restore all of your data [or as much as you want], from bare metal if necessary. Mondo is in use by Lockheed-Martin, Nortel Networks, Siemens, HP, IBM, NASA's JPL, the US Dept of Agriculture, dozens of smaller companies, and tens of thousands of users.
Dar: dar is a shell command that backs up directory trees and files. It has been tested under Linux, Windows, Solaris, FreeBSD, NetBSD, MacOS X and several other systems
Many commercial or free software back up tools are also available.
Types of Backup
There are different kinds of backups, the following lists some of them:
Full Backup
Full backup is the starting point for all other backups, and contains all the data in the folders and files that are selected to be backed up. Because full backup stores all files and folders, frequent full backups result in faster and simpler restore operations. Remember that when you choose other backup types, restore jobs may take longer.
Advantages
Restore is the fastest
Disadvantages
Backing up is the slowest
The storage space requirements are the highest
Incremental Backup
Means backing up everything that has changed since last full backup. Advantages
Backing up is the fastest
The storage space requirements are the lowest
Disadvantages
Restore is the slowest
Differential Backup
Differential seems to be another name for incremental.differential backup offers a middle ground by backing up all the files that have changed since the last full backup
Advantages
Restore is faster than restoring from incremental backup
Backing up is faster than a full backup
The storage space requirements are lower than for full backup
Disadvantages
Restore is slower than restoring from full backup
Backing up is slower than incremental backup
The storage space requirements are higher than for incremental backup
Network Backup
Network backup usually means backing up a client to a backup server, this means the client sends the files to the server and the server writes them to backup medium.
Dump Backup
Dump backups are not ordinary file by file backups. The whole disk partition or file system is "dumped" to the backup medium as is. This means it is also necessary to restore the whole partition or file system at one go. The dump backup may be a disk image, which means it must be restored to a similar disk with same disk geometry and bad blocks in same places. Watch out for this.
Level 0 -- 9 Backup
Level 0 to 9 backups are a finer grained version of incremental backups. Level N backup means backing up everything that has changed since a same or lower lever backup.
Check the backup can be restored, with original file owners, permissions and timestamps.
To be useful, you must be able to restore the backup. Very often not only the contents of file are important, but their time stamps, permissions and owners. Check that you can restore the backup so that all these are preserved.