Thursday, April 30, 2009
The Tiny Unix And Linux Shell Crash Course For Beginners
Hey there,
Today's been a long day, filled with fun and gainful employment. Unfortunately, nothing I did today was the least bit interesting to write about ;)
So, in the mean time - in between time - I came up with a little something to help a few new guys get used to the shell (bash in this instance, but most of this will work in any shell... except the c shell - nothing is compatible with the c shell except tcsh and ...the c shell ;)
The setup is simple for this crash course, and (we'll consider ourselves the teachers) you should let the student know that they're in for a fun little piece of problem solving. Maybe, if I had the time to give this some more thought, it could be a pretty decent (although probably unusually cruel ;) interview tactic. If you have the time (and the stomach) to do that to some poor bastard that's looking to make a buck; go for it. I'm a pretty harsh interview, but I don't know if this is something I'd do to someone who didn't already know that their future employment was ensured (pending the outcome of drug testing, of course. Quite frankly, if you don't have what it takes to do your job while you're loaded to the gills, I don't think you'll not be able to see right through my fragile mask of sanity ;)
Anyway. Load up your mark's .profile (or .bashrc, etc) with this little collection of shell aliases and see how long it takes them to break out and get a normal shell back. Plenty of folks can do it without thinking. Anyone who can't will learn a little something.
And, please remember, this isn't about judgement; it's about pushing someone (even yourself) to think outside the box (or whatever object they're figuratively trapped in ;). We all need to be able to think in that abstract space every once in a while. Why not make it fun :)
Cheers,PS1="youAreHere/ "
export PS1
alias --='-'
alias ash='echo youAreHere/ '
alias bash='echo youAreHere/ '
alias cat='perl -l'
alias cd='cd .'
alias cp='echo cp'
alias csh='echo youAreHere/ '
alias df='echo /dev/dump 100% 100% 0% /tmp/jailfs/hoosegow/you'
alias echo='echo '
alias emacs='ed'
alias env='vmstat'
alias ex='ed'
alias exec='echo cannot fork'
alias exit='echo are you sure?'
alias id='echo user\(me\) group\(sadly the same\)'
alias joe='ed'
alias jsh='echo youAreHere/ '
alias kill='echo all dead'
alias ksh='echo youAreHere/ '
alias less='more ---x'
alias logout='echo are you sure?'
alias ls='echo .'
alias mkdir='echo making directory'
alias more='less </dev/null'
alias mv='echo stay'
alias netstat='cat /dev/random'
alias ping='ping /dev/null'
alias prompt='echo youAreHere/'
alias ps='echo you 501 501 0 Apr 1 ? 0:00 /usr/bin/vicks -vaporub'
alias pwd='echo you are here'
alias rm='echo can\'\''t find'
alias rmdir='removing directory'
alias set='iostat'
alias sh='echo youAreHere/ '
alias su='echo cannot su to'
alias sudo='exec'
alias touch='echo please don\'\''t touch'
alias unalias='echo no aliases found named'
alias vi='ed'
alias vim='ed'
alias w='echo x, y and z'
alias who='echo what?'
alias zsh='echo youAreHere/ '
# alias alias="sleep 5"
# Uncommenting that last line is optional ;)
, Mike
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Wednesday, November 28, 2007
Disabling Network Devices in the Solaris Boot PROM
There are quite a few bugs out there on SunSolve, regarding system crashes due to this or that network device failure (or driver issues, depending on how you look at it). Most of the time, the advice is to disable the network device as non-destructively as possible. That can be difficult, given the right circumstances. Of course, I'm talking about the "non-destructive" part. Disabling an interface is easy. Lots of people who don't know the first thing about Solaris can do it, if they bang enough keys and have the proper system privilege ;)
The first thing to do is incredibly obvious. Just take out any references to the network device on the host. Say, if you are using ce0 and ce1 and no longer want to use ce1, you could just do the following and you'd be good from that point on and for future reboots:
ifconfig ce1 down
ifconfig ce1 unplumb
rm /etc/hostname.ce1
vi /etc/hosts <--- Optional, to remove ce1 host name/IP entry
vi /etc/netmasks <--- Optional to remove ce1's netmask setting (unless it's on the same subnet as ce0!)
vi OTHER_FILES <--- Any pertinent files were you may have inserted special route commands, etc, that are no longer applicable
The second thing to look for would be OS operations you could perform (perhaps during boot up). As a "For Instance," certain Sun machines, running certain patch levels, have an issue with the hme0 network device (it's technically a device driver) if it's not connected to the network. Even if you aren't using it. This is somewhat annoying because, if you don't set up the configuration to plumb the network device and bring it up, it shouldn't give you any errors. You should only know hme0 exists by looking in a system file like /etc/path_to_inst. But the hme0 device causes the following error to post constantly during boot up and for a while after:
SUNW,hme0:Parallel detection fault
Working around this bug is fairly simple. In this case (and each case will probably be slightly different - troubleshooting can be long and hard some times), you could run the first two lines below, to stop the activity immediately, while logged in. The second line could be added to /etc/system so that the problem wouldn't recur on reboot. It is strongly recommended to backup, or copy off, /etc/system before changing it, so you can use "boot -a" at the PROM level to boot using your old version if the new one causes your future boots to fail!
ndd -set /dev/hme instance 0
ndd -set /dev/hme adv_autoneg_cap 0
set hme:hme_adv_autoneg_cap=0>>/etc/system
The third, and most drastic, way you'd go about this is to disable the problematic network device at the Solaris PROM level. Before you bring the machine down, run this (we're still using hme0 as an example and note the output by copying and pasting into notepad, or even writing it down:
grep hme /etc/path_to_inst
"/pci@1f,4000/network@1,1" 0 "hme" <--- This is the device (instance 0 of hme, or hme0) that we want to disable!
"/pci@1f,4000/SUNW,hme@5,1" 1 "hme"
Assuming we've already executed something like "init 0" as the root user, we could do the following to disable hme0 from the PROM "ok" prompt. Note that if you run "show-nets" at the PROM level and see truncated information, use it to compare with the device you have listed from before and use the most similar (just slightly clipped) entry in your future arguments.
If none of the patterns match at all, you may have gotten the wrong info from /etc/path_to_inst or your device tree is screwed up beyond what we're specifically dealing with here today. At this point you should be absolutely certain you know which network device to disable at the PROM level. Now, run the following to make the PROM disable, and Solaris forget all about, hme0:
ok nvedit
0: probe-all install-console banner
1: " /pci@1f,4000/network@1" $delete-device drop
2:
ctl-c <--- Typing the control key and the c key together will break you out of nvedit and put you back at the ok prompt
ok nvstore
ok setenv use-nvramrc? true
use-nvramrc? = true
ok reset-all <--- Make sure you enter a line with "set auto-boot? false" before you run this command, if you want your system to stay at the PROM after it resets.
Now, the hme0 network device should finally be completely disabled at the OS level. Solaris should not even know it exists! You may want to consider doing a reconfigure boot ("init 0" followed by "boot -r" at the PROM "ok" prompt or "reboot -- -r" from the OS -- there are a few more ways to do it, but I digress).
And, to answer the inevitable, and reasonable, question: How can I re-enable my network device on Solaris' PROM once I've disabled it?, here's how:
ok setenv use-nvramrc? false
ok nvedit
0: " /pci@1f,4000/network@1"
delete-device
ctrl-u <--- Hitting the control key and u key together will delete the current line from the nvedit buffer. You only need to do this for the device you previously wanted to ignore.
ctrl-u <--- You usually won't have to type this twice. This is just to demonstrate that you can erase as many lines in the buffer as you want before exiting your nvedit session. In this case, you must delete two lines since the device and delete-device instruction are on separate lines.
ctrl-c
ok nvstore
ok reset-all
ok boot -r
Hopefully this has saved you more headaches than it can potentially cause :)
, Mike
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