OpenSSH 7.0 & greater disable ssh-dss by default. http://bit.ly/2vZBMyH If you upgrade OpenSSH, to 7.1.102.1100 on AIX for example, you may notice that you're unable to login afterwards, with ssh-dss keys. In syslog you'll see messages similar to this:   Syslog: Sep 11 15:40:34 cgaix auth|security:info sshd[9961802]: userauth_pubkey: key type ssh-dss not in PubkeyAcceptedKeyTypes [preauth]   # lslpp -l openssh\*   Fileset                      Level  State... [More]

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Before I describe the sudo problem I hit, I will tell you that the root cause of the problem is evident in the following output:   # mount   node       mounted        mounted over    vfs       date        options -------- ---------------  ---------------  ------ ------------ ---------------         ... [More]

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Using PowerSC RTC to monitor for the deletion of a specific file.   One of my customers was concerned that someone or something was randomly deleting the /etc/niminfo on several of his AIX hosts. We discussed several ways in which he could track down who or what was removing this file. Obviously, the AIX audit subsystem would be an ideal method of capturing this event. However, PowerSC Real Time Compliance (RTC) can also monitor and capture this type of event.   “The PowerSC™ Real Time Compliance feature continuously... [More]

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The AIX minidump facility was introduced with AIX 5.3 TL3. A mini dump is a small compressed dump that is stored to NVRAM when a system crashes or a dump is initiated, and then written to the AIX error log on reboot. It can be used to see some of the system’s state and do some debugging when a full dump is not available. It can also be used to get a quick snapshot of a crash without having to transfer the entire dump from the crashed system to IBM support.   Please refer to the following, official guide, on " How to examine a... [More]

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The latest release of the VIOS provides a way to automatically backup your virtual device configuration whenever it changes. From the IBM Knowledge Center for POWER8:   https://www.ibm.com/support/knowledgecenter/POWER8/p8hcg/p8hcg_viosbr.htm   "The viosbr command automatically creates a backup, whenever there are any configuration changes. This functionality is known as the autoviosbr backup. It is triggered every hour, and checks if there are any configuration changes, or any other changes. If it detects any changes, a backup... [More]

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On more than one occasion I’ve written articles and blogs on how to migrate AIX systems to a new version of the AIX operating system. You can find a list these articles (and others) here . Each of the NIM articles focuses on migrating AIX systems (which are configured as NIM clients). The approach is always the same; use a NIM master to migrate the NIM clients to the next release of AIX. What they don’t discuss is how to migrate your NIM master to a new version of the OS. This is the very first step you should take before you... [More]

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I LPM'ed an AIX LPAR from Frame A to Frame B. The LPAR id before the LPM was 99 and after the LPM it's still 99. And the system id has changed, as expected. Good.   Before migration.   root@lpar1 / # uname -L 99 lpar1   root@lpar1 / # lsattr -El sys0 -a systemid systemid IBM, 017268B60 Hardware system identifier False   After migration.   root@lpar1 / # uname -L 99 lpar1   root@lpar1 / # lsattr -El sys0 -a systemid systemid IBM, 0157F5B16 Hardware system identifier False   Great, that's exactly... [More]

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AIX has a new “critical volume group” capability which will monitor for the loss or failure of a volume group. You can apply this to any volume group, including rootvg. If applied to rootvg, then you can monitor for the loss of the root volume group.   This feature may be useful if your AIX LPAR experiences a loss of SAN connectivity e.g. total loss of access to SAN storage and/or all SAN switches. Typically, when this happens, AIX will continue to run, in memory for a period of time and will not immediately crash. Often you... [More]

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Whilst working with one of my AIX customers recently I discovered a problem with NIMSH and SSL. The customer had updated their NIM master from AIX 7.1 TL4 SP1 to AIX 7.1 TL4 SP3 . After the SP update, any attempt to connect to a NIM client (over NIMSH+SSL), from the NIM master, would simply hang. For example, we tried to list the filesets on the NIM client with this command, which never returned any output.   [root@750lpar4]/ # nim -o lslpp 750lpar9   The /var/adm/ras/nimsh.log file, on the NIM client, showed that the NIMSH session... [More]

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Recently I've come across an odd issue at two different customers. I thought I'd share the experience, in case others also come across this strange behaviour.   In both cases they reported j2pg high CPU usage .   Similar to this...   And, in both cases, we discovered many /usr/sbin/update processes running. Unexpectedly .   When we stopped these processes, j2pg's CPU consumption dropped to nominal levels.   The j2pg process is responsible for, among other things, flushing data to disk and is called by the... [More]

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AIX 7.2 requires 2GB of memory to boot, but this minimum is not enforced in the LPAR profile except by Live Update (to ensure we'll be able to boot the surrogate LPAR). You can check your Minimum Memory setting in your LPARs profile by running the lparstat command (as shown below).   # lparstat -i | grep Memory Online Memory                              : 4096 MB Maximum Memory                        ... [More]

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Enabling TCP large send offload (LSO), on AIX, is generally considered a good thing. It helps with overall network performance.   Taking advantage of networking large-send large-receive https://www.ibm.com/developerworks/community/wikis/home?lang=en#!/wiki/W51a7ffcf4dfd_4b40_9d82_446ebc23c550/page/Taking%20advantage%20of%20networking%20large-send%20large-receive   TCP large send offload “This option improves the performance on 10 Gigabit Ethernet and faster adapters for workloads that manage data streaming (such as file transfer... [More]

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You can use the HMC lssvcevents command to view DLPAR event history. In the following example, I’m looking for “Add processor” related DLPAR events, over the last 30 days, for a specific LPAR.   $ lssvcevents -t console -d 30 | egrep 'Add processor|DLPAR' | grep s82861p22_nim   time=12/01/2016 00:48:33,text=HSCE2209 User name hscroot: DLPAR Add processor resources to partition s82861p22_nim succeeded on managed system Server-8286-42A-SN214F55V   Search for all DLPAR events over the last 30 days.   $... [More]

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Here’s some handy tips and tricks for managing WPARs in your AIX environment.   How to share a global file system with a WPAR.   - In the Global.   root@750lpar11]/ # uname -W 0   - Global File System that you want to share with the WPAR (750wpar2).   [root@750lpar11]/ # df -g /cg Filesystem    GB blocks      Free %Used    Iused %Iused Mounted on /dev/cglv          1.98      0.30  ... [More]

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When troubleshooting Fibre Channel adapter issues on AIX (or VIOS), I often use the fcstat command to assist me in the process. The command may display error numbers similar to the following:   $ fcstat fcs0   Error opening device: /dev/fscsi0 errno: 00000045   The error number (errno) displayed can (in some cases) be used to identify the root cause of a problem. In the example above, the error number is 45 . This number is in hex. If we convert this to decimal, the number is 69. Now, if we look for 69 in the /usr/include/errno.h... [More]

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There may be better ways to do this, and if there are, please let me know. But lately I've been "hacking around" with cloud-init on AIX and trying to make it behave the way I want it to. There were two problems I faced and solved.   My first challenge. The AIX /etc/hosts file isn't updated with the IP address and hostname of the new AIX VM after deployment from PowerVC. To work-around this niggle*, I added the following short but effective shell script to the Activation Input in the PowerVC GUI.    #!/bin/ksh... [More]

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My colleague in Lab Services, Ben Swinney, recently configured the Virtual HMC on his Apple Macbook. He was kind enough to write up his experience, so that others could also run the vHMC on their Mac. Me included!  You can find Ben’s instructions here: https://www.ibm.com/developerworks/community/blogs/cgaix/resource/vHMC_running_on_Apple_hardware.pdf Thanks Ben!  

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At the IBM Technical Symposium in Sydney last week, a person approached me to discuss NIM and some of its capabilities. During the conversation we discussed how NIM could be used to copy files from the NIM master to its NIM clients. I promised to send them some information on how to achieve this ASAP. They were smart and followed up with an email the next day! They’d even tried to configure this on their systems but hit a small problem.   "Hello Chris,   So trying to push out a new netbackup tar file to one of our nim... [More]

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Do you use SSL with nimsh on AIX? No? Well, you might want to consider it. If you regularly use LPM to migrate AIX partitions from one server to another, you may have found that, on occasion , your NIM master has trouble communicating with its NIM clients afterwards. This is by design, as nimsh uses the NIM clients cpuid to authenticate with the NIM master. During an LPM operation, the cpuid of the NIM client changes and its possible the NIM master may reject the client as a result. This problem can occur even when CPU validation is disabled on... [More]

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Is that a versioned WPAR? Use the lswpar command and the –G option to determine the WPAR type. Yeah, I could use clogin and then run oslevel , but this is faster!   [root@gibopvc1]/ # lswpar -G p8wpar1 ================================================================= p8wpar1 - Active ================================================================= Type:                    S RootVG... [More]

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On the odd occasion, NIM may report that a resource is allocated to a NIM client, when, in fact, it is not. Typically, you’d check that the resource was, in fact, not allocated for use to any NIM client and if it was, you would reset the client; and this would resolve the issue. But if that doesn’t work, you may need to take an additional action to resolve the problem. This doesn’t happen very often but it can frustrate you when it does.   Here’s an example of the problem. I try to remove an lpp_source resource but... [More]

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There’s a new NIM HTTP service handler included with AIX 7.2 (due for release next month, December 2015).  This new service is designed “…….to help Clients better conform to emerging data center policies restricting the use of NFS, NIM will now have support to apply updates to AIX or install new packages over HTTPs.   Initial AIX installs will still require the use of NFS version 3 or the more secure NFS version 4 protocol.   In addition to fileset installs, NIM customization activities such as script... [More]

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I enjoy it when I open my email in the morning and find a new message with a subject line of “ weird one… .”! I immediately prepare myself for whatever challenge awaits. Fortunately I do delight in helping others with their AIX challenges so I usually open these emails first and start to diagnose and troubleshoot the problem!   This week I was contacted by someone that was having a little trouble with a mksysb backup on one of their AIX systems.   “Hi Chris, This one has me stumped, any ideas? I’ll have... [More]

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In my previous post on AIX Live Updates I discussed how to use the geninstall command to perform a non-disruptive (ifix) update on an AIX system. In this post I wanted to show you how to perform the same task using NIM.   NIM can be used to start an AIX Live Update operation on a target machine (NIM client) either from a NIM master or from the NIM client itself (with nimclient ).   Note: The AIX Live Update operation started by NIM calls the hmcauth command during the cust operation to authenticate to the NIM client with the HMC by... [More]

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