Friday, December 14, 2012

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.$ ping
PING ( 56(84) bytes of data.
64 bytes from ( icmp_req=1 ttl=50 time=61.3 ms
64 bytes from ( icmp_req=2 ttl=50 time=63.2 ms
[1]+  Stopped                 ping$ exit
There are stopped jobs.$ 

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


How to retain job running though you try to logout?
Just press below commands/shortcuts


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


Sunday, December 2, 2012

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

Saturday, November 17, 2012

'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.

Sunday, October 14, 2012

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.

Wednesday, October 3, 2012

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.

(98)Address already in use: make_sock: could not bind to address no listening sockets available

Solution for (98)Address already in use: make_sock error

The error

(98)Address already in use: make_sock: could not bind to address no listening sockets available

is commonly seen when we are starting a network related service such as Apache(httpd), DNS(bind) squid etc.

When and Why this error occurs?

This error occurs when service tried to bind that particular port to the IP address. In other words for example there is service ABC running on port 443 and you tried to start some other service XYZ on the same port with out knowing that ABC service is running on that 443 port.

Technical details?

When ever you want to run a network related service we have to bind this service to a port and IP address so that once its assigned what ever packets coordinated to that service are routed through this port.

What about Solution?

Step1: First you have to check what service is running on that IP address by using nmap port mapping tool.

From the above error I am taking my IP as


Sample output nmap localhost

Starting Nmap 5.21 ( ) at 2012-10-03 12:35 IST
Nmap scan report for
Host is up (0.0000090s latency).
Not shown: 997 closed ports
53/tcp   open  domain
443/tcp  open  sshd
3689/tcp open  rendezvous

Nmap done: 1 IP address (1 host up) scanned in 0.25 seconds

Step2: Once you find the service name which occupies the port try to stop if the service is not required.

service sshd stop

Step3: Now start your Apache service and this error will vanish.

Tuesday, October 2, 2012

All about Linux and Open source errors with their solutions

The idea of this blog is simple. This is totally meant for the errors which are seen daily when we are configuring some servers, applications, tools etc. I felt there is no dedecated blog which deals only with errors related to Linux, Unix and open source tools which work on Linux/Unix based flavors. This site is for those people who are looking for the errors they are seeing on day to day activities.

What you will see in this blog?

All about errors and their solutions so that you no need to scratch your head on what went wrong in creating this error?

Can any one contribute to this site?
Yes, All are welcome. A person in this world will never come across all the problems faced by other users. So it should be corroborated way rather than one man army.

Surendra Anne.