User:Ascensus

Linux System Administration Notes
For security updates only:

yum install yum-security

To use this plugin to update your computer to the latest security fixes, just use

yum --security update

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I was getting this error on l1 after imaging and doing a "module avail"

/usr/local/Modules/3.2.2/bin/modulecmd: error while loading shared libraries: libtclx8.3.so: cannot open shared object file: No such file or directory

solution: yum install tclx

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SSH Frequently Asked Questions My SSH client connects, but the server seems to immediately close the connection. I get "connection closed" or "connection lost," or with OpenSSH:

ssh_exchange_identification: Connection closed by remote host This message means that the client got a TCP connection to the server, but the server immediately closed it before the SSH protocol could get started (the ssh_exchange_identification routine implements the version string exchange, the initial step of the protocol).

This usually happens because of a libwrap setting which prohibits the connection. Check the server log; if this is the problem, you will see messages like these:

SSH1, OpenSSH sshd1[15092]: refused connect from 192.168.10.1 SSH2 sshd2[15085]: Denied connection from by 192.168.10.1 tcp wrappers.

If you compiled the SSH server with libwrap (TCP-wrappers) support, check that the rules in the files /etc/hosts.{allow,deny} on the server host allow connection to the SSH daemon. An entry like this, for example, will allow connections to sshd from any source address:

sshd sshd1 sshd2 : ALL : ALLOW

The name on the left must be the argv[0] value of the running daemon, so if you've invoked sshd under another name, you'll need to use that. Also, the rules are order-dependent, so the rule just given might not work, depending on the other rules and their relative placement. See the hosts_access(5) man page for details on the libwrap rule syntax and semantics. © 2001-2008 Barrett, Silverman, & Byrnes

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