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If you are doing some tests which require reboots (e. g. startup skripts, kernel module parameters, ...), this is very time intensive, if you have got a hardware with a long pre-boot phase due to hardware checks.
At this time, kexec can help, which only restarts the kernel with all related stuff.
First the kernel to be started is loaded, then kexec -e jumps up to start it.
Is as hard as a reboot -f, but several times faster (e. g. 1 Minute instead of 12 on some servers here).
Converts any number of seconds into days, hours, minutes and seconds.
sec2dhms() {
declare -i SS="$1"
D=$(( SS / 86400 ))
H=$(( SS % 86400 / 3600 ))
M=$(( SS % 3600 / 60 ))
S=$(( SS % 60 ))
[ "$D" -gt 0 ] && echo -n "${D}:"
[ "$H" -gt 0 ] && printf "%02g:" "$H"
printf "%02g:%02g\n" "$M" "$S"
}
This is super fast and an easy way to test your terminal for 256 color support. Unlike alot of info about changing colors in the terminal, this uses the ncurses termcap/terminfo database to determine the escape codes used to generate the colors for a specific TERM. That means you can switch your terminal and then run this to check the real output.
$ tset xterm-256color
at any rate that is some super lean code!
Here it is in function form to stick in your .bash_profile
aa_256 ()
{
( x=`tput op` y=`printf %$((${COLUMNS}-6))s`;
for i in {0..256};
do
o=00$i;
echo -e ${o:${#o}-3:3} `tput setaf $i;tput setab $i`${y// /=}$x;
done )
}
From my bash_profile: http://www.askapache.com/linux-unix/bash_profile-functions-advanced-shell.html
swap out "80" for your port of interest. Can use port number or named ports e.g. "http"
Stuck behind a restrictive firewall at work, but really jonesing to putty home to your linux box for some colossal cave? Goodness knows I was...but the firewall at work blocked all outbound connections except for ports 80 and 443. (Those were wide open for outbound connections.) So now I putty over port 443 and have my linux box redirect it to port 22 (the SSH port) before it routes it internally. So, my specific command would be:
$iptables -t nat -A PREROUTING -p tcp --dport 443 -j REDIRECT --to-ports 22
Note that I use -A to append this command to the end of the chain. You could replace that with -I to insert it at the beginning (or at a specific rulenum).
My linux box is running slackware, with a kernel from circa 2001. Hopefully the mechanics of iptables haven't changed since then. The command is untested under any other distros or less outdated kernels.
Of course, the command should be easy enough to adapt to whatever service on your linux box you're trying to reach by changing the numbers (and possibly changing tcp to udp, or whatever). Between putty and psftp, however, I'm good to go for hours of time-killing.
From the manpage:
$ man less
-X or --no-init
Disables sending the termcap initialization and deinitialization strings to the terminal. This is sometimes desirable if the deinitialization string does something unnecessary, like clearing the screen.
Bonus:
If you want to clear the screen after viewing a file this way that had sensitive information, hit or just type clear. Since is readily available, I don't know why less bothers to automatically clear. If you're viewing the file at all, chances are you want to see the output from it after you quit.
Instead of looking through `lsof` results, use inotifywait!
