error: Requested operation is not valid: Disk does not support snapshotting

error: Requested operation is not valid: Disk  does not support snapshot

This error arises when you try to take a snapshot of a VM hard disk with virsh command
as shown below


virsh snapshot-create Clusterbase

error: Requested operation is not valid: Disk '/path/to/kvm/clusterbase.img' does not support snapshot.

If you see image of this VM is .img format, by default Virsh snapshot will work only for qcow2 format as of time of this post writing. So first convert that image to qcow2 format and then try to do a snapshot t with same command.

Convert img file to  qcow2 format


qemu-img convert -f raw -O qcow2 /path/to/kvm/clusterbase.img /path/to/kvm/clusterbase.qcow2

Hope this helps to resolve this error.

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Loaded plugins:fastest mirror Loading mirror speed from cached hosfile Setting up install process Nothing to do

Q. I am seeing below error when installing some packages


 Loaded plugins:fastest mirror
  Loading mirror speed from cached hosfile
  Setting up install process
  Nothing to do

This error will come when you execute below command

yum install somepackage

and the repo is set with "enable=0", try to change it or use --enablerepo= as shown below.

yum --enablerepo=yourreponame install somepackage


If you set enable=0 that indicates that dont include this repo when installing RPM packages. And enable=1 will include this repo when installing packages.

Hope this helps some one.

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error: command 'save' requires option

This error will come when you are trying to save VM using virsh command. When you try to save VM status using Virt-manager we no need to mention any file to save the status. Virt-manager will take care of saving it. But virsh have no mechanism like this. We have to provide a file to save the machine status.

virsh save domaname filename

Example
virsh save linux1 /opt/linux1.stat

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Failed to mount ': Input/output error NTFS is either inconsistent, or there is a hardware fault, or it's a SoftRAID/FakeRAID hardware.

Q. I am getting following error when I mounted my external HDD in Ubuntu Linux and getting below error.

root@linuxnix.com:~# mount -t ntfs /dev/sde1 /mnt
$MFTMirr does not match $MFT (record 0).
Failed to mount '/dev/sde1': Input/output error
NTFS is either inconsistent, or there is a hardware fault, or it's a
SoftRAID/FakeRAID hardware. In the first case run chkdsk /f on Windows
then reboot into Windows twice. The usage of the /f parameter is very
important! If the device is a SoftRAID/FakeRAID then first activate
it and mount a different device under the /dev/mapper/ directory, (e.g.
/dev/mapper/nvidia_eahaabcc1). Please see the 'dmraid' documentation
for more details.

This error usually occurs

• When computer shutdown/restarted/suspended/hibernated
• Not properly mounted etc.

To fix this issue you have to install ntfsprogs which will provide fixing of 

As a root run below command

apt-get install ntfsprogs

Fixing by using ntfsfix as root

ntfsfix /dev/sde1

Once this is fixed you can try to mount once again.

mount -t ntfs /dev/sde1 /mnt

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mount: could not find any free loop device

mount: could not find any free loop device solution

This is the error you will get when mounting an ISO or img file. This is due to limitations of number of loop devices available in a machine. To eliminate this error we have to unmount unnecessary images before mounting any other image file in the machine.

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Linux error "There are stopped jobs"

This error will come when you try to logout or exit from a terminal and there are some tasks which are running in background. 

surendra@linuxnix.com:~$ ping linuxnix.com

PING linuxnix.com (216.239.38.21) 56(84) bytes of data.

64 bytes from any-in-2615.1e100.net (216.239.38.21): icmp_req=1 ttl=50 time=61.3 ms

64 bytes from any-in-2615.1e100.net (216.239.38.21): icmp_req=2 ttl=50 time=63.2 ms

^Z

[1]+  Stopped                 ping linuxnix.com

surendra@linuxnix.com:~$ exit

There are stopped jobs.

surendra@linuxnix.com:~$ 

If you observe I started a ping program and sent that process to background. And when I try to logout from that terminal I got an error stating that there are still some programs running. To stop this error we have to see if you really like to kill the jobs.

How to kill those jobs?

Execute/press below commands/shortcuts

fg

ctrl+c

How to retain job running though you try to logout?

Just press below commands/shortcuts

ctrl+z

bg

disown

This will allow us to run the process in background though you try to logout.

 

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Solution of "No Route to Host error" Issue

No Route to Host error Linux solution

Q. I am seeing an error when trying to connect to a server, but I am able to ping and see other ports open by using telnet command? Is there a solution to resolve this issue?

First of all check what are open ports on that machine

nmap server-ip

Check if your service is running and showing in nmap output.Check if your service is running or not on tha

If your port is not open check your iptables output.

iptables -L

This will show all the rules. You can flush the iptables if you are not much concern about security.

iptables -F

Stop iptables and save iptables

service iptables stop
service iptables save

Perminently off iptables service.

chkconfig iptables off

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'main' not defined in your config (for this host).

This is the error you will see when configuring drbd(Distributed Replicated Block Device). This is caused when the main resource in not defined in any or .res files in /etc/drbd.d folder. So check you defined main as resource in the .res files or not. If its defined and you feel there is no config error, check if the host name is matching in the res file to the uname -n command

uname -n

if you see the difference between the names then change the config files according to the uname -n command output.

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WARNING: Re-reading the partition table failed with error 16: Device or resource busy

WARNING: Re-reading the partition table failed with error 16: Device or resource busy

We will see this error from RHEL6 on words. This error is due to the partition table changes are not updated to kernel. When ever we change the partition table and try to save the table changes we get this error. Even you will get the following error as well


The kernel still uses the old table. The new table will be used at
the next reboot or after you run partprobe(8) or kpartx(8)
Syncing disks.

when you see this error and executing partprobe command can not do anything, in RHEL5 based partprobe is the command to update the partition table changes to kernel, but from 6 we have to use partx command to update the partition table changes to kernel. 

Use below command to update the partition table changes.

partx -a /dev/sda

This will update the partition table changes of /dev/sda hard disk to the kernel.

Try to run above command two times, because first time it will try to sync previous partition table changes.

Hope this helps some one.

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Failed to connect socket to '/var/run/libvirt/libvirt-sock': Permission denied

Failed to connect socket to '/var/run/libvirt/libvirt-sock': Permission denied

This error will occurs if the user do not have permissions to connect to virt-manager or virtviewer tools.
To resolve this issue execute below commands

Step1: Conform if your root user account have permissions or not

virsh -c qemu:///system list

if you dont see any issue from root user, try to execute the same command with normal user where you want to start virt-viewer or virt-manager. If you see any issues such as "failed to connect socket" issue with normal user then he should be member of libvirtd group first. Follow below procedure.

Step2: Add the user account as secondary group member to libvirtd group

Note: Before doing anything keep in mind that this user may be member of many other already existing groups so add this user account to them as well.

usermod -G libvirtd,group2,group3 -a username

Step3: Now we have to change the settings in /etc/libvirt/libvirtd.conf. Open /etc/libvirt/libvirtd.conf as root and search for following lines and remove the comments for that lines.
vi /etc/libvirt/libvirtd.conf
Now remove comments from the lines which contains below info.

unix_sock_group = "libvirtd"
unix_sock_ro_perms = "0777"
 unix_sock_rw_perms = "0770"

With the first line we are mentioning that libvirtd group is allowed to very one and r/o and r/w permissions for all the users who belongs to this group.

Hope this helps some one.

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