A while back I wrote a post Analyzing Linux System Performance and Finding Bottlenecks. I did’t really give a good explanation of determining if you are CPU bound or not so I am writing this post to clear that up.
Have you ever experienced hard lockups and seen no trace of the cause in your log files? Those situations can be even more of a pain if you do not have physical access to the machine since you will not be able to look for kernel oops on the console. You could buy a serial console or an ip kvm but if you don’t have the need for remote control, but would really like to be able to debug without being physically present you need to check out netconsole. Netconsole sends printk messages over UDP.
Ever run into a situation where passing the option single to the kernel wasn’t enough to get your root password reset? This is not Debian specific but some distros (including Debian) require that you still enter the root password when booting to single user mode. This is just a quick run through of how to reset your root password without a live cd. Reboot your system and at the grub prompt hit e to enter edit mode, then select the kernel line and hit e again. Now append single init=/bin/bash to the line. Hit enter to temporarily save it and hit b to boot. Shortly you will be dropped at a root prompt, now you just need to remount your root file system rw so you can update the passwd.
I was restoring some files from backup today and ran into a few files that had leading slashes. Whenever I see those kind of things I rename the files since they are a pain to work with in the shell. If you find yourself at a shell and need to work with files that have a leading dash just use the relative path and include the dashed filename in quotes.
I posted about Tom Limoncelli and his Time Management for System Administrators. I have written a simple wrapper to do pre and post processing of a todo file as it is opened and closed to somewhat mirror “the cycle”. If your interested you can find a bit more information on todo-cycle here.
It’s not new news but I havent seen anyone else mention it. Ben Rockwood over at cuddletech had his second SA Pro podcast with Tom Limoncelli, it covers time management. It’s a good listen, I’m still waiting for him to setup a feed for the podcasts. Tom has some good advice, I have picked up a few things and read his Time Management for System Administrators since listening to the podcast.
Im sure everyone is familiar with smb messages especially as everyone was assulted with them about 10 years ago (stupid soho routers and spammers unite!). Anyway, there are clients for linux like Linpopup. Well recently I didn’t want to use one of those to be able to send messages to my linux workstations so I cobbled together a simple network popup app with python.
I just wanted to make sure no one forgets that wildcards can be used in your .ssh/config. This can be extremely helpful. For example say you have 100 nodes that have a simple nameing scheme of nodexxxx. You can add the following into your ssh config and pre-poplulate settings. Host node* User staffuser IdentityFile ~/.ssh/staff_key That would cause any ssh connection matching node* to use the user staffuser and .
With small websites sometimes you need to put up a maintenance page while you are making some modifications. Typically you should have some staging enviornment but sometimes infrastructure does not allow for this. If you find your self in this situation you might like this tip.
I use vim for the vast majority of my editing. It can be a bit cumbersom to hit esc each time you want to perform a command while in insert mode. Using ctrl o will put you in command mode for the next command. Give it a try sometime it may or may not make you more effective with vim.