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Side effects of patching

News Enterprise Unix System Administration Recommended Links Simple Unix Backup Tools Unix rm command Unix mv command
Absence of backup Rush/absence of testing Creative uses of rm Abuse of privileges LVM and disk related mishaps Working on the wrong computer
Safe-rm Typical Errors In Using Find Tips Unix History Humor Etc

Patching horrors are much more common then you would suspect. Some companies (Sun) test patches pretty well. Other (IBM, HP) less well. Some (Novell) introduce important changes via patches which can lead to completely hosed system.

It goes without saying that patches. and, especially, service packs need to be tested on quality server before being applied to production server.  The most deadly situations arise when the system patched has complied Sendmail, Bind or other popular open source package. Such packages are often overwritten during patching with unpredictable results. 

Even without custom components installed applying service packs can be very interesting experience:

The best way to install service packs is using installation DVD (which has an upgrade option). Attempts to do it from Novel website using regular patch mechanism are more risky. 

At the same time expect troubles in any case and reserve enough downtime. Testing in the lab is a necessary preliminary step for production servers. Do not dive blindly. It might not reveals all the problems that you might encounter on a production server but it tremendously helps.

SP3 is actually more like a major upgrade then a service pack. For example, it tries to convert /boot to /by-uud/ format (and often screw /boot partition as a result).  For example all partitions not controlled by LVM will be mounted using /by-id/ scheme, for example:

/dev/disk/by-id/scsi-36001ec90e5265400103d932e4fea1f42-part2 /boot ext3 acl,user_xattr 1 2

After the upgrade most server have the problem with the multipath driver which is installed by default.  It can demonstrate itself  in two ways:

If the server does not use multipath driver the easiest way to fix this problem is to disable it. You can boot into rescue mode, mount /boot partition and disable multipath on /boot/grub/menu.lst by adding multipath=off to the kernel directive. The other way to solve this problem is to manually rebuild initrd. Both fixes are not permanent and will probably be overwritten by the next fixpack (SP3 actually reliably wipes out multipath=off from /boot/grub/menu.lst).

Its unclear what to do if multipath is really used on the server. In this case it might make sense not apply online patches after upgrading to SP3 or stay with SP2 and wait until SP4 will be available. 

Dr. Nikolai Bezroukov


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[Jun 19, 2010] Sysadmin horror story

May 06 2000 | Everything2.com

A story of a novice or inattentive sysadmin wiping out vital parts of a computer system by such commands as "rm -rf /" or "rm /vmunix". It becomes more horrific if there were no readable backups.

Here's the worst thing I have yet done as a sysadmin. I had to upgrade several machines from HP-UX 9 to HP-UX 10. Having done the workstations with reasonable ease, I set aside a Saturday to do the departmental mail server. I installed HP-UX 10 from the CD-ROM HP had sent me with no problems, just a long wait spent reading Usenet on my laptop, made our standard local modifications and checked that email was up again.

Then I had a large number of patches to install from another CD-ROM from HP (both CD-ROMs were part of their Year 2000 Transition Kit). This meant another long wait, and it was quite late in the afternoon by the time they had installed. I thought that since these patches came directly from HP, and the system had been fine before I installed them, it was unlikely that it would suddenly stop working. So I let it reboot and went home without testing it.

On Monday morning, I found out that email had completely stopped working. Eventually I discovered the reason why. On our systems, /usr/sbin/sendmail is a link to /usr/sbin/exim, which is a link to the real exim, which is on the /usr/dpmms filesystem on our mail server, which is NFS-exported to our other machines. I had been careful not to overwrite anything on /usr/dpmms during the install. However, the patch program (swinstall), on being asked to replace /usr/sbin/sendmail, had followed the chain of links and replaced the REAL exim with sendmail! As you can imagine, my users were not happy about the long disruption to email. Fortunately I was able to restore exim from a working backup tape.

Linux kernel 2.6.33 released - openSUSE Forums

Re: Linux kernel 2.6.33 released

Quote:

dale14846 View Post

Does this mean that the factory kernel that panics during boot will soon be fixed? There's nothing wrong with the 2.6.33 kernel, at least the mainline one. Works here for me. The only thing that's not working is the nvidia driver which won't compile if you get the stable official one (190.53) and not the beta (or apply the patch to the 190.53 driver which lives somewhere on the gentoo bugzilla - the one on the nvidia forum is flawed). In 2.6.33, kernel internals changed so the 190.53 driver is not compatible with the changes, thus fails to compile. It seems the beta driver does support the new kernel version

Now if you get a kernel panic from the factory kernel, that's a different issue. A kernel won't panic if it can't load a module (because it's either not present or can't be loaded, esp if the module is a video driver). There's something else going on with the factory kernel

PS: I stopped using SUSE kernels a while ago, they seem to always introduce some problems and the way they split the kernel in a gazillion different packages, I find ridiculous. I switched to mainline kernel and have been happy ever since (also had much less issues with it). But yeah, this requires some knowledge on how to properly configure and compile mainline kernel, which luckily I have Re: Linux kernel 2.6.33 released


On 02/25/2010 11:26 AM, dale14846 wrote:
>
> microchip8;2126710 Wrote:
>> 'Linux 2 6 33 - Linux Kernel Newbies'
>> (http://kernelnewbies.org/Linux_2_6_33)
>>
>> Compiling now

>
> Does this mean that the factory kernel that panics during boot will
> soon be fixed?

There was a problem with a long-standing kernel bug that was activated by the
switch to gcc 4.5. If that was the one that got you, then it is fixed, but that
has nothing to do with the usage of 2.6.33-rcX kernels.

[Sept 15, 2003] Fix-It Fatigue By John Foley, George V. Hulme.

Patching became a problem and not only on Microsoft operating systems ;-)

With the Blaster worm seeming to be under control, alleged virus-author Jeffrey Parson under house arrest in Minnesota, and hacker Adrian Lamo under the watchful eye of the feds, business-technology managers may have enjoyed a few hours of peace and quiet last week. But it was short-lived. On Sept. 10, Microsoft issued a security bulletin warning of three new critical vulnerabilities in the Windows operating system, sending systems administrators rushing to patch their computers. It's become an all-too-common scenario--and one that's causing some businesses to re-evaluate their heavy reliance on Microsoft products.

A year-and-a-half after Bill Gates declared that trustworthy computing had become Microsoft's No. 1 priority, the software bugs keep coming. The latest vulnerabilities involve the Remote Procedure Call service in Windows, making it possible for a malicious hacker to take control of a target system, introduce an infectious worm, or launch a denial-of-service attack. A week earlier, Microsoft issued five other warnings, four involving the omnipresent Office applications suite. For the year, the tally stands at 39.

And those are just the holes that have been uncovered by others and reported to Microsoft. In addition, the software vendor is combing through its code, finding holes, and issuing patches without publicizing the flaws. No one knows how many more are yet to be uncovered. "There's no way to wrap your hands around that," says Dan Ingevaldson, engineering manager with security vendor Internet Security Systems Inc.

Some business and technology professionals are running out of patience. "The issues around these vulnerabilities are escalating to the point where it's not just CIOs or CTOs, it's corporate officers, it's boards of directors asking: 'What are we going to do?'" says Ruth Harenchar, CIO of Bowne & Co., which last week scrambled to patch 4,500 Windows PCs and 500 servers in the United States and more overseas. "The situation appears to be getting worse, not better."

The patching work has thrown Bowne & Co.'s technology projects off schedule. Now, the specialty-printing-services company is assessing its options. Among them: redesigning its network around a thin-client model to reduce the number of PCs running Windows and, on other machines, migrating to Linux. "It's getting to be enough of a burden that you have to seriously start thinking about alternatives," Harenchar says.

Raymond James & Associates has assembled a team of IT staffers to manage the constant patching. "Organizations have to mobilize and realize this is going to be a way of life for the foreseeable future," says VP of IS Gene Fredriksen.

The financial-services firm, with offices around the world, last week began the arduous task of patching 10,000 PCs and 1,000 servers. "The pressure is on," Fredriksen says. "Anybody that isn't patched by the weekend is going to have trouble." The fear is that the latest vulnerability leaves Windows computers open to a Blaster-like worm. "There's a very good chance that a worm is going to be developed" to take advantage of the latest security holes, says ISS's Ingevaldson.

"People are getting fed up," says Lloyd Hession, chief information security officer at financial-network provider Radianz, adding that the number of Windows patches is reaching "epic proportions." The situation is causing more than just a few disgruntled customers to re-evaluate how much they use Microsoft products. Says Gartner security analyst John Pescatore, "There's definitely a very large trend towards that."

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