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Troubleshooting Unix / Linux Servers

Troubleshooting tips about Linux, *BSD, UNIX, Apple OS X, programming and MS-Windows servers and desktop systems ( rss feed ).

I'm trying to login using ssh keys but server is only allows to login me using a password. The following message is logged into server /var/log/secure file:

Feb 25 06:36:50 ns5 sshd[26681]: Authentication refused: bad ownership or modes for file /home/user/.ssh/authorized_keys2

How do I fix this problem?
[click to continue…]

Q. How do I turn on DNS server logging so that I can see all the queries on my CentOS 4.0 server?

A. You can use rndc command which controls the operation of a name server. It supersedes the ndc utility that was provided in old BIND releases. If rndc is invoked with no command line options or arguments, it prints a short summary of the supported commands and the available options and their arguments.

rndc communicates with the name server over a TCP connection, sending commands authenticated with digital signatures. In the current versions of rndc and named named the only supported authentication algorithm is HMAC-MD5, which uses a shared secret on each end of the connection. This provides TSIG-style authentication for the command request and the name server\u2019s response. All commands sent over the channel must be signed by a key_id known to the server.

Task: Turn on logging

Type the following command as root to toggle query logging:
# rndc querylog

Task: View bind sever query log

Once this is done, you can view all logged queries usimg /var/log/messages file. To view those queries, type:
# tail -f /var/log/messages

Task: Turn off logging

Type the following command as root to toggle query logging:
# rndc querylog

Q. I’m using Fedora Core Linux. Recently I changed my ISP. Now I get error as follows when I try to start PPP:

PPP authorization failed
Machine not authorized to use this PPP address

How do I fix this problem?
A. PPP is the protocol used for establishing internet links over dial-up modems, DSL connections, and many other types of point-to-point links. The pppd daemon works together with the kernel PPP driver to establish and maintain a PPP link with another system (called the peer) and to negotiate Internet Protocol (IP) addresses for each end of the link. Pppd can also authenticate the peer and/or supply authentication information to the peer. PPP can be used with other network protocols besides IP, but such use is becoming increasingly rare.

Auth option require the peer to authenticate itself before allowing network packets to be sent or received. This option is the default if the system has a default route.

By adding noauth option you can get rid of this problem. It means ppp do not require the peer to authenticate itself. Open /etc/ppp/options file:
# vi /etc/ppp/options
Append option:
Save and close the file. Now run ppp and you should able to connect.