Securing OpenSSH

I was recently researching the latest guidance on securing OpenSSH and came across a web page on a popular site espousing that the easiest way to protect OpenSSH is to define a login banner. While a login banner is useful, especially in a enterprise setting, it’s useless for securing SSH. So, here is my recipe for securing OpenSSH. While testing these, ALWAYS keep a connection open. It’s very easy to break something and if you don’t already have an open connection, you will have successfully locked yourself out.

Stor2RRD Overview

If you manage your own SAN, you’ll eventually be asked questions like “Why are some of my databases slow?”, “Why do we periodically have performance problems?” or “Do we have a hot LUN?”. Modern arrays have real-time performance monitoring, but not all of them have historical data so you can see if there’s a periodic performance issue or if the current performance is out of the ordinary. There are vendor supplied products and lots of third party products that let you gather performance statistics, but they’re usually pretty expensive. If you just need to gather and report on the performance data for IBM V7000, SVC, or DS8000 storage, there is a great FREE product call Stor2RRD.

Linux LUN Resize

I recently had someone ask me how to rezise a LUN in RHEL without rebooting. The “go-to” method for this admin was to reboot! This is easily accomplished in AIX with “chvg -g”, but how to do this in Linux wasn’t so obvious.

In my example, I’m using LUNs from a SAN attached XIV storage array, using dm-multipath for multipathing and then LVM for carving up the filesystems. After the LUN is resized on the storage array (96Gb to 176GB in my case), we have to scan for changes on the SCSI bus. I’m assuming you have the sg3_utils package installed to get the scsi-rescan command. The simplest thing is to just rescan them all, though you can do them individually if you want:

Is it Power7 or is it Power7+?

Is it live, or is it Memorex?UPDATED

Last year I budgeted for 3 P740C model’s to replace 3 P6 550 models that were getting long in the tooth. Because of the long lead time in our budget process and the continued downward pressure from IBM on their pricing, I was able to purchase 4 P7+ 740D models.  That is a big win for us.

After implementing new 7042-CR7 model HMCs (which I recommend everyone upgrade to) and powering on our first box, I noticed that the latest HMC code reports the server has a Power7 and not a Power7+.  The Power7 chip has been out for nearly a year, and the HMC has been through several updates since then, so why does it not show Power7+ the way it did for Power6+?  Here’s what the screen looks like:

Privileges Necessary for MySQLDump

I recently setup a backup process to dump a MySQL database to a file for backup. With this database, our DBA group has been using the ‘root’ account setup the by software vendor for administration. This server is used for internal system administration and sending performance data off to our software vendor. So, other than being bad form to use the ‘root’ ID, there’s probably no regulatory responsibility to use user or role specific IDs.

Sending AIX Syslog Data to Splunk

I recently put up a test Splunk server to act as a central syslog repository, one of the issues in our security audits. There are some “open” projects to do this, but Splunk has a lot of features and is “pretty” compared to some of the open alternatives. Getting data from our Linux hosts was a snap, but data from our AIX hosts has a few minor annoyances. Fortunately, we were able to overcome them.

TSM Deduplication Increases Storage Usage (for some values of deduplication)

I ran into an interesting problem recently. A de-duplicated pool containing TDP for Oracle backups was consuming much more space than would otherwise be indicated. Here’s what the occupancy looked like:

Node Name         Storage         Number of     Logical
                  Pool Name           Files     Space
                                                Occupied
                                                (MB)
----------        ----------    -----------    ----------- 
CERN_ORA_ADMIN    CERNERDISK            810      31,600.95 
CERN_ORA_BUILD    CERNERDISK          1,189      74,594.84 
CERN_ORA_CERT     CERNERDISK            402   3,876,363.50 
CERN_ORA_TEST     CERNERDISK            905   7,658,362.00
LAW_ORA_PROD      CERNERDISK          1,424     544,896.19 
OEM_ORA_RAM       CERNERDISK          2,186     524,795.31

That works out to about 12.7 TB. And, here’s what the storage usage looked like:

Installing the XIVGui on Fedora 16

I’ve been running the XIVGui on a Windows7 VM so that I have it available from anywhere. That does work, but then I have to launch an rdesktop session, login, then launch the XIVGui, and login again. I finally got tired of the extra steps and decided to load the XIVGui when I upgraded to Fedora 16. I considered making an RPM, but I’m sure IBM would frown on redistributing their code. These manual steps work great on Fedora 16, should work fine on Fedora 15. I haven’t tested it with RHEL or other versions.

Static DHCP IPs with KVM Virtualization

When building a virtualization lab system, I’ve found that I want static IPs assigned to my guests. You could just assign static IPs in the guest OS, but then you should document what IPs are in use for what hosts. It would be easier to just assign static IP entries in the DHCP server. There doesn’t seem to be a straight-forward way to get this done.

What I’ve found works is to destroy the network, edit it directly, and then restart it.

TSM Windows Client OS Level Demystified

The client OS level field in TSM for most operating systems is pretty straightforward. On Linux, it’s the kernel version, HP-UX and AIX show a recognizable OS level. For windows the OS level is more cryptic. Here is a list of the OS levels:

Operating System Client OS Level
Windows 95 4.00
Windows 98 4.10
Windows ME 4.90
Windows NT 4.0 4.00
Windows 2000 5.00
Windows XP 5.01
Windows Server 2003 5.02
Windows Vista 6.00
Windows Server 2008 6.00