Warning personal rant follows.
Over the years I have used a number of different flavours of Unix/Linux. Unix flavour I have used include AIX (IBM), SunOS/Solaris (Was Sun, now Oracle), IRIX (SGI), HPUX (HP), Ultrix (DEC). Linux flavours include Suse, Mandrake, Mandriva, Redhat, Fedora, DSL, Puppy and many more.
When I first started with AIX, I had come from the world of the Apple Macintosh that was all nice a fluffy - you did most things point and click (except for development). The shock was large, I had to write some shell scripts and some C programs. vi was the most unpleasant piece of crap I had ever seen. So I took a couple of days out and compiled emacs on the AIX machine. For the next year or so was happy in the world of emacs.
That was of course until a machine had a major issue and I needed to start it in maintenance mode. Then you get a scaled back OS to fix the machine with, and you guessed it vi was the editor.
Over time I then had to administer other machines with other versions of Unix, some of these had emacs, but all had vi. It suddenly dawned on me I need to take the time to learn vi. From that point forward I have never looked back, I would struggle now to drive emacs.
The thing that has become clear to me in the world of computer administration is take the time to learn all the standard tools and the standard ways to do things - if you rely of having a customised environment you will spend a lot of time building the custom environment each time you have a new machine to look after, rather than getting on with the job at hand.
The world is different if your job is that of programmer and you spend all your time on one computer, customise your environment on the machine, to minimise the amount of time doing all the other activities that do not involve writing code.
I expect all aspiring linux/unix sysadmins to learn vi, sed, awk, shell scripting and even perl. The mark of a true sysadmin is when the GUI starts the first application they run is a terminal to get to the command line, and this is where they spend most their time. Otherwise you are just a hobbyist (there is nothing wrong with having a hobby), and the title System Administrator becomes devalued.
Also take the time to learn as many tools and technologies as you can. Each one you learn makes you more valuable to the world of IT, gives you more depth and once you move to jobs where you are given the task to architect a system you have a better understanding of more tools. Too many systems are built using the wrong tools just because they are the only ones people know.
Thursday, September 15, 2011
Sunday, September 11, 2011
After Update, FC15 does not start correctly
From time to time there are various problems after an update that result in the machine not getting all the way to the GUI prompt after an update. With a little bit of knowledge this becomes a less concerning issue, and can be quite easily fixed.
My most recent experiences of this were a few weeks ago, I ran a yum update - there was a new kernel package installed, but the graphics drivers from rpmfusion had not been released for the kernel. As a result the machine appear to hang during boot at the point when it should have started X11.
To help with these issues, the first thing I do when I install linux is edit the grub.conf file and change the timeout parameter from 0 to 3. This puts a 3 second pause in the startup, that allows you to press a key and get a boot menu up, that allows you to select an older kernel to boot. (You can also change the command line it uses to start the kernel). When you then have these problems you can simply use this menu to boot the previous kernel.
Even without this, you can switch to another terminal session on your console with CTRL-ALT-F2 (F3, F4...) CTRL-ALT-F1 will get you back. You can then log in and get a command line.
When things get really bad you will need to get out you linux install media and boot off that, to get a command line to perform the recovery.
No matter how you do it, once you have a command line you can fix your install.
Most often you can fix it by changing the default boot kernel to the previous one. Edit the /etc/grub.conf file - the line to edit the default=0, this is a reference to the first OS entry in the file, to boot using the second one change it to default=1.
Another technique is to use yum to roll back the changes, as described in yum - help I have broken my install
Another thing to consider if you are taking a lot of updates and often have problmes is to change the number of kernels that are allowed to be installed at one time. This is done in the /etc/yum.conf file, you can change the line installonly_limit=3 to a higher number. I usually set mine to 5 just to have a bit more buffer when things start to go wrong.
One of the realities of linux is that it is more stable a reliable on slightly older hardware that the drivers have had the bugs ironed out in them. When you are in the situation I have been lately where some of the hardware I have is only just supported in the latest release then this is when stability issues come to the fore.
My most recent experiences of this were a few weeks ago, I ran a yum update - there was a new kernel package installed, but the graphics drivers from rpmfusion had not been released for the kernel. As a result the machine appear to hang during boot at the point when it should have started X11.
To help with these issues, the first thing I do when I install linux is edit the grub.conf file and change the timeout parameter from 0 to 3. This puts a 3 second pause in the startup, that allows you to press a key and get a boot menu up, that allows you to select an older kernel to boot. (You can also change the command line it uses to start the kernel). When you then have these problems you can simply use this menu to boot the previous kernel.
Even without this, you can switch to another terminal session on your console with CTRL-ALT-F2 (F3, F4...) CTRL-ALT-F1 will get you back. You can then log in and get a command line.
When things get really bad you will need to get out you linux install media and boot off that, to get a command line to perform the recovery.
No matter how you do it, once you have a command line you can fix your install.
Most often you can fix it by changing the default boot kernel to the previous one. Edit the /etc/grub.conf file - the line to edit the default=0, this is a reference to the first OS entry in the file, to boot using the second one change it to default=1.
Another technique is to use yum to roll back the changes, as described in yum - help I have broken my install
Another thing to consider if you are taking a lot of updates and often have problmes is to change the number of kernels that are allowed to be installed at one time. This is done in the /etc/yum.conf file, you can change the line installonly_limit=3 to a higher number. I usually set mine to 5 just to have a bit more buffer when things start to go wrong.
One of the realities of linux is that it is more stable a reliable on slightly older hardware that the drivers have had the bugs ironed out in them. When you are in the situation I have been lately where some of the hardware I have is only just supported in the latest release then this is when stability issues come to the fore.
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