Stuck with DHCP Client Error: mv cannot move /etc/resolv.conf.dhclient-new to /etc/resolv.conf: Operation not permitted? We can help you.

This error indicates that dhclient (Dynamic Host Configuration Protocol Client) is unable to update the name resolution configuration file /etc/resolv.conf.

We use dhclient command to obtain, renew and release a client’s IP address, subnet mask, default gateway, and DNS servers from a DHCP server.

Here at Bobcares, we often get requests from our customers to fix similar DHCP Client Error as a part of our Server Management Services.

Today let’s see how our Support Techs fix this error for our customers.

How does a typical ‘DHCP Client Error: mv cannot move’ look like

The dhclient command provides a means for configuring one or more network interfaces using the Dynamic Host Configuration Protocol, BOOTP protocol, or if these protocols fail, by statically assigning an address.

The error message is given below:

Next we will see the cause for this error.

Common Cause of this Error

The dhclient prepares a temporary file with the new nameserver details in /etc/resolv.conf.dhclient-new and then tries to rename it as /etc/resolv.conf.

Generally, it generates an error because /etc/resolv.conf is already bind-mounted and apparently mv is not allowed to do this trick.

/etc/resolv.conf.dhclient-new.xxx are the temporary files the DHCP client daemon writes before moving the complete file to /etc/resolv.conf.

This is to keep the consistency of the actual /etc/resolv.conf file if something goes wrong.

Sometimes the DHCP client will not be able to write the /etc/resolv.conf file/is dying, and the temporary files keep behind.

How to fix DHCP Client Error: mv cannot move

Following are the steps that our Support Techs follow to fix this error:

1. Firstly, we must run dhclient as the root user

We can use the following sudo command to run dhclient, enter:

$ sudo dhclient eth0

2. After that we should ensure that /etc/resolv.conf is not write protected

We can use the following lsattr, command to view file attributes:

$ lsattr /etc/resolv.conf

Output:

----i------------- /etc/resolv.conf

Generally, we cannot modify a file with the i attribute. We can either delete it or rename it. Also, no link can be created to this file and no data can be written to the file for any user including the root user.

Clear i attribute, enter:

$ sudo chattr -i /etc/resolv.conf

Now run dhclient again to update the file and to obtain a new IP address.

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Conclusion

In short, we saw how to fix DHCP Client Error: mv cannot move, along with the steps that our Support Techs follow to fix this error.