Category: linux

(sorry if this should not make any sense to you. This is a note for me to go back to. Even though I bring new machines online regurlarly I forget the exact steps for this)

on X
ssh-keygen -t dsa

add content of .ssh/id_dsa.pub in the end of .ssh/authorized_keys2 on Y. Only thing we need to do on Y.

after boot of X run

ssh_info_file=~/.ssh-agent-info-`hostname`
ssh-agent >$ssh_info_file
chmod 600 $ssh_info_file
source $ssh_info_file
ssh-add ~/.ssh/id_dsa


before login from X to Y
source /root/.ssh-agent-info-hostname

sar from the sysstat modules is nice. I think it keeps about a weeks worth of history around. I’d like to have more than that. There might even be a command lines switch to do that. But often it is just faster to write what you need when you can type with reasonable speed. This script will copy all sa files into a directory called /var/log/allsa in the form saYEARMONTHDATE. So today’s sa file I can access forever via


sar -f /var/log/allsa/sa20090822


The script only cares about files that are older than a day. So it will take between 24 and 48 hours that the files appear in their final destination.


#!/usr/bin/perl

foreach my $file (@allfiles){
if ($file =~ /^sa[0-9]+$/){
my $completefilepath = "$sourcedir/$file";
my $mtime = (stat $completefilepath)[9];
my $dayage = (time() - $mtime ) / ( 3600 * 24 ) ;
if ($dayage > 1){
my ($sec,$min,$hour,$mday,$mon,$year,$wday,$yday,$isdst) = localtime ( $mtime);
my $datestring = sprintf ( "%d%0d%02d" , $year + 1900, $mon + 1, $mday);
my $targetfilepath = "$targetdir/sa$datestring";
if (! -f "$targetfilepath"){
#print "$file $dayage $datestring\n";
system ("cp -p $completefilepath $targetfilepath");
if (! -f "$targetfilepath"){
die "tried to copy from $completefilepath to $targetfilepath and it did not work. This is a very bad sign!";
}
if (((stat $completefilepath)[7]) != ((stat $targetfilepath)[7])){
die "file sized for $completefilepath and what should have been a copy $targetfilepath did not match. Not good!";
}
}
}
}
}


shells keep a history. The default seems to be to keep 1000 lines. I have not found a reason to make this huge. And while at it time stamp it as well:


HISTFILESIZE=2000000
HISTSIZE=100000
HISTTIMEFORMAT='%F %T '
export HISTTIMEFORMAT HISTSIZE HISTFILESIZE


in your .bashrc will keep 100,000 lines (2MB “omg” ) of history around and will also time stamp it nicely. That and the grep command make for some nice shortcuts on memory lane.

When I wanted to build php with imap it did complain about:


configure: error: Kerberos libraries not found.


Turns out that this some fallout from lib64 vs. lib differences. So I found
this blog explaining exactly what was going on. Very helpful. Especially the


sh -x ./configure ...options go here...


trick can be very very helpful in the future.