SFTP connection error

One of my customer mentioned to me that SFTP problem.

Question: I found an error message on /var/log/messages as below:

fatal: mm_request_receive_expect: read: rtype 48 != type 46
fatal: mm_request_receive_expect: read: rtype 48 != type 46

while make a SFTP(SSH) connection using Ipswitch WS_FTP Professional client.

Solution: Make changes on SSH config file
Edit /etc/ssh/sshd_config and change PasswordAuthentication to yes. Restart SSH services.

What is PasswordAuthentication? Change to No for disable tunneled clear text passwords.
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August 6, 2008 · Filed Under Open Source, Tips

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SSH known_hosts Cheat Sheet

Secure Shell or SSH is a network protocol that allows data to be exchanged using a secure channel between two computers. SSH uses public-key cryptography to authenticate the remote computer and allow the remote computer to authenticate the user.

In order to use public-key secure connection with other Linux hosts (ssh, scp, sftp) there is a special directory, ~/.ssh/, where passphrases and public keys are stored. Normally you wouldn’t need to know the gory details, but from time to time a host will change its public key and then you have difficulty using ssh, sftp or scp with that host, and have to edit a file named known_hosts.

If you try to ssh to another computer, but get an error message that warns about a changed or incorrect public key, then it is probably just a case of that host changing its public key. (It is possible, though usually not the case, that malicious hacking is involved.) Unless you actually suspect hacker involvement, you can edit the file ~/.ssh/known_hosts using your usual text editor (vi, emacs, or pico) and delete any line with the name or IP address of that host. Then when you try to ssh that host again, it will be like the first time ever; ssh will ask you if you want to accept a new public key, you type the whole word yes, and everything will proceed normally from there.

Said for an example, I have a Linux cluster running on 2 machines(active/passive mode) and usually users are connect using a virtual hostname or virtual IP address. Whenever Linux cluster or heartbeat switches over to the second machine and you try to ssh to it, ssh will reply with a WARNING: REMOTE HOST IDENTIFICATION HAS CHANGED! Annoying right?

So?

How to ignore SSH known_hosts in these case?
How to make SSH known_hosts work for cluster environments?

SSH known_hosts cheat sheet

Imagine you have the 2 cluster machines node1 and node2 with virtual hostname running as below:

node1 – IP address: 192.168.1.1
node2 – IP address: 192.168.1.2

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June 9, 2008 · Filed Under How's To, Open Source, Tips

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How to add a raw mapping device on VMware

VMware ESX Server offers two choices for managing disk access in a virtual machine—VMware Virtual Machine File System (VMFS) and raw device mapping (RDM). It is very important to understand the I/O characteristics of these disk access management systems in order to choose the right access type for a particular application. Choosing the right disk access management method can be a key factor in achieving high system performance for enterprise-class applications.

Basically you can read few VMware RDM related guide from VMware such as: http://www.vmware.com/pdf/esx25_rawdevicemapping.pdf and http://www.vmware.com/resources/techresources/1040

I would like to share “How to add a raw mapping device on VMware” in my VMware ESX development box together with SuSE Linux Enterprise Server 9 VMware guest.

Click on SLES 10 VMware guest in my Virtual Infrastructure Client
Click Edit Setting
Click Add
Select Hard Disk
Click Next
Selecet Raw Device Mappings
Click Next
Select Target LUN
/vmfs/devices/disks/vmhba0:0:16:0
/vmfs/devices/disks/vmhba0:0:22:0
Click Next
Select Store with Virtual Machine OR Specify datastore
Click Next
Select Compatibility
Choose physical (allow the guest operating system to access the hardware directly. Taking a snapshot of this virtual machine will not include this disk)
For Virtual (it’s allow the virtual machine to use VMware snapshots and other advanced functionality
Click Next
Select Virtual Device Node -> SCSI (0:1)
Click Next
Ready to Complete
Click Finish
Click OK

Done!

As you can see from pictures show above, SLES 9 with 200G Raw Device Mapping Drive created.

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May 3, 2008 · Filed Under How's To, Tips, VMware

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Disable Root Login on Linux

How to disable root login on Linux system?

There are several ways to do that such as:

1)To prevent users from logging in directly as root, the system administrator can set the root account’s shell to /sbin/nologin in the /etc/passwd file. This will prevent access to the root account through commands that require a shell, such as the su and the ssh commands. Edit the /etc/passwd file and change the shell from /bin/bash to /sbin/nologin.

#vi /etc/passwd
->search for to root and change /bin/bash to /sbin/nologin

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February 16, 2007 · Filed Under Open Source, Tips

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SSH Root Access Login Control

After read “OpenSSH Root user account restriction – revisited” article, I did a test on my testing server.

The pam_access PAM module is mainly for access management. It provides logdaemon style login access control based on login names, host or domain names, internet addresses or network numbers, or on terminal line names in case of non-networked logins.
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August 3, 2006 · Filed Under How's To, Open Source

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