I just read this comment about Unix permissions in a whitepaper to do with securing databases. The comment is about Progress databases, which may not exist in your environment, but the comment is worth noting anyway:   Though counterintuitive, file modification is controlled by permissions on that file, but file creation and deletion are controlled by permissions on the parent directory. In other words, it is entirely legal to delete a file that you cannot modify if you have write access to the directory without having write access to the file... [More]

Tags:  security permissions read_write chmod umask unix_permissions chown

When you create a file system using SMITTY, the default action is for the file system NOT to mount after a reboot. Now it might occur to you that generally when you create a file system, you probably want it to be available after a reboot. So you naturally hit the F4  key (or Esc 4  or just the Tab  key) so that you can set the option to True.   Here's what to do if you've forgotten that option and found your file system hasn't mounted after a reboot.   From the command line:   The fix is quite easy using the chfs command, and you don't need to... [More]

Tags:  filesystems geek_of_the_week jfs2 mount

A mksysb backup of the root volume group (rootvg) includes the file  /etc/filesystems . This configuration file includes file systems from other volume groups (like datavg) and maybe NFS mounts. When you  restore from the mksysb , those other file system entries must be cleaned up, or you'll get mounting errors when you reboot. Here's how to do that cleanup. But first, a comment from an annoyed reader:   "What's the fuss about?"   Response: You may be thinking this is no big deal. You can always ignore errors (sigh!). Well, if you... [More]

Tags:  mksysb /etc/filesystems restore datavg clone

You can create a file using the AIX touch command. The touch command is used to update a file's timestamp, but if the file doesn't exist, then the touch command creates it. That's an easy way of creating a lock file - the sort of file you use to alert the world that they can't log in because some process is running - or a trigger or flag file whose existence is a signal to some script or program to begin the next process.   Trigger Happy   The problem with creating an empty lock/flag/trigger file is that no one knows where it came from. You may... [More]

Tags:  touch lock_file timestamp trigger_file flag_file

Someone asked me to remove all empty directories in a particular path.   Option 1: rm -r You can remove ALL directories and all files using  rm -r You will end up with a nice clean system that way, and a new line on your resumé explaining why you left your job at short notice. DON'T TRY THIS AT WORK! For that matter, don't try any of these "solutions" until you've tried them somewhere which doesn't leave you wishing you'd never heard of AIX Down Under . Whenever I run any command to remove files or directories, I waste two seconds... [More]

Tags:  mkdirhier mkdir cleanup remove empty_directory yuk rmdir directory

Free Blog Downgrade for all our followers     After violent battles and verbal exchanges which were unbecoming to AIXers, the team of writers and editors here have finally opted for a minimal theme for the blog. We here in Sydney have been working around the clock (it took a good two minutes) to use a mobile-friendly  Minimal Theme . What does this mean for you?  full support for SmartPhone and tablet views a Twitter widget Trending topics ... and plenty more. AIX Down Under should be faster and slicker. In short, a better experience for you.

Tags:  aixdownunder blog mobile

After restoring a mksysb to a new logical partition the reboot hung with the AIX IPL progress code "0551" "IPL Vary-on is running." After trying slight variations in the profile the boot process hung at "Starting kernel". The rootvg couldn't be varied on, and I didn't know why. The solution was simple, as you'll see. Troubleshooting the boot As part of the troubleshooting process, I booted the logical partition off the AIX Product Media. I was able to Access the root volume group, and recreate the boot image using... [More]

Tags:  boot_failure starting_kernel 0551 led

If you want to get a view of the process tree, you could try it using the ps command, but there's a better way: the proctree command. You can see all of its parent processes and its child processes. Here's how it looks.   This is an installation of IBM Systems Director Management Server version 6.3.    # ./dirinstall.server -B /database --DB=1 +=============================================================================+ Start of product installation on myhost +=============================================================================+  ... [More]

Tags:  process proctree ibm_systems_director director

For network redundancy, you can set up two Shared Ethernet Adapters (SEAs) - one on each Virtual I/O Server (VIOS). The two SEAs work together with one active, the other idle, so the configuration is called failover mode. This is done by a control channel - a heartbeat that works through a virtual ethernet adapter on each SEA. The failover mode is very effective, because it allows you to shut down a single VIOS and automatically have the other SEA on the alternate VIOS take the traffic. With failover mode you can use VLAN tagging, something not... [More]

Tags:  virtual_io_server sea shared_ethernet_adapter load_sharing vios virtual_switch

Some time ago I experimented with removing the default paging space /dev/hd6 from an LPAR and creating a separate volume group for paging space . This worked ... until I had to restore a mksysb backup, as you may recall from this blog pos t.   Well, what about creating a separate paging space in rootvg instead of in a separate volume group, and then removing hd6? Not exactly sure why you'd do that, but I suppose if you were to create a smaller paging space to replace hd6, in case it's been extended too much, that might be a reason. Whatever... [More]

Tags:  paging_space hd6

One of the great strengths of AIX is the Logical Volume Manager (LVM). It may not be completely foolproof, but it does provide quite a lot of protection from administrator errors. Here are a few common LVM tasks that I've deliberately attempted to make a mess of. See how the LVM reacts   (Don't Try This at Home) Let's start with three Physical Volumes. rootvg has one PV (booting from SAN) and datavg has two PVs. # lspv hdisk0 00c5a47ecf9edd3e rootvg active hdisk1 00c5a47ed021ea7d ... [More]

Tags:  logical_volume_manager exportvg umount mount lvm varyoffvg

There are no coincidences.   Whenever I hear of any sort of problem at all, I wait to see if an entirely unrelated problem is reported soon after. This is especially worthwhile for performance issues, or when something suddenly stops working.   I came across a site where a printer was down. Within half an hour a controller error was reported from a disk subsystem which wasn't used by the system that had the printer go down. Coincidence? I was suspicious. Temporary problem: permanent solution We soon found out that the printer was down because... [More]

Nigel Griffiths (of IBM Power Systems Advanced Technology Support, Europe - but he is also known as Mr Nmon) gave a great presentation on Shared Storage Pools at Copenhagen. This was also presented in the excellent Webinar Series on Power Systems Virtualisation .   Here's a small extract on why you would use Shared Storage Pools:   In smaller companies, there is no SAN team. The server guys are the SAN guys. The idea of Shared Storage Pools is to allocated LUNs to the VIOS(s) and a single VIOS command can allocate space to a... [More]

Tags:  vios thin_provisioning

Whenever I see a script with a five or ten minute wait in it, I ask myself what it's waiting for. I recently saw a script which started a database, waited 10 minutes (using sleep 600), then started an app server (sleep 600), then started another application (sleep 600, then exit!). That script gets a lot of sleep.   The reason behind the delays was to wait for the previous process to complete. But that could be confirmed in a few ways. Ordinarily, the previous command will have an exit code which you can test for, or you could... [More]

Tags:  wait script sleep

If you've been following this blog for a while, you might remember a post on the Systems Management Interface Tool (SMIT), better known as SMITTY to his friends . That post covered the frequently-asked question about the difference between smit and smitty . It also provided some handy SMIT Keyboard shortcuts.   Well, here are some new keyboard shortcuts that should be real time savers for you. They're not strictly new, as they're about 25 years old, but some of them were new to me, and they may be to you. Some of them are real gems, such as the... [More]

Tags:  smit smitty keyboard shortcut

It wasn't a hostile question from a bean counter looking to cut costs. It was from a visitor - a school student on work experience (a week or two of trying out life in "the real world"), and I was asked what I did. How could I answer that? "AIX"? Too vague and obscure for someone who's not in the industry. System administration? So does the guy who supports the laptops. How about "I manage stuff that no one understands"? How do you justify your existence in 30 seconds?   I looked over my day, and thought about how... [More]

Tags:  job_description

If you mix production and non-prod LPARs on the same managed system, you may be worried that the non-prod LPARs could chew up much-needed production processing juice. What are your options here? Here are some common solutions: A separate shared processor pool for Prod systems Capping the non-prod LPARs Implicit capping of non-prod LPARs This last option is dealt with in a Redpiece (part of the Redbooks) called " SAP Applications on IBM PowerVM ". The Redpiece is in draft format..Even if you're not running SAP, it provides a good... [More]

Tags:  vcpu virtual_processor lpar

The team from IBM in the UK have been running some great webinars, and the next one promises to be a beauty. It's on Virtualisation (British spelling) Best Practices.   A small error in the beginning is a big error in the end. It's true in philosophy, it's true in maths (British usage), it's true in taking directions and it's true in setting up your virtualised environment. It's much easier to use good planning before implementation than to have to untangle everything afterward.   This webinar promises to cover how to: plan document implement... [More]

Tags:  virtualisation webinar aix

If you thought IBM Watson winning Jeopardy! was just a gimmick, think again. There are people who have seen Watson in action and say: "I want one!" IBM has now established a Watson Solutions team.   I understand that Watson is going to be back in the spotlight very soon, with a re-broadcast of the Jeopardy shows in the week of 12 September.   It sounds like there's a lot more planned to apply Watson's technology in various industries. I found a video of how Watson answers questions very interesting. As they say in the video:. "A... [More]

Tags:  watson jeopardy!