Restoring a file that still has an open filehandle on Linux

My rm /var/log/access_log* was a little greedier than I wanted it to be. What I meant to use was rm /var/log/access_log.* :-( . Never fear, apache didn't know I had deleted the file as it had an open filehandle and was happily logging away, but how to restore it? Check out the step by step:

# lsof | grep access_log
apache2    1649       root    8w      REG        8,1        0    4334715 /var/log/apache2/access_log (deleted)
apache2   15265   www-data    8w      REG        8,1        0    4334715 /var/log/apache2/access_log (deleted)
apache2   15266   www-data    8w      REG        8,1        0    4334715 /var/log/apache2/access_log (deleted)
# cd /proc/1649/fd
# ls -alh
total 0
dr-x------ 2 root root  0 2009-11-17 18:31 .
dr-xr-xr-x 7 root root  0 2009-11-17 16:15 ..
lr-x------ 1 root root 64 2009-11-17 18:32 0 -> /dev/null
l-wx------ 1 root root 64 2009-11-17 18:32 1 -> /dev/null
l-wx------ 1 root root 64 2009-11-17 18:32 2 -> /var/log/apache2/error_log
lrwx------ 1 root root 64 2009-11-17 18:32 3 -> socket:[5823]
lrwx------ 1 root root 64 2009-11-17 18:32 4 -> socket:[5824]
lr-x------ 1 root root 64 2009-11-17 18:32 5 -> pipe:[576841]
l-wx------ 1 root root 64 2009-11-17 18:32 6 -> pipe:[576841]
l-wx------ 1 root root 64 2009-11-17 18:32 8 -> /var/log/apache2/access_log (deleted)
# cat 8 > /var/log/apache2/access_log && /etc/init.d/apache2 stop && /etc/init.d/apache2 start

Woot!

Making sure PTR records and A records match

DNS is so simple! Unfortunately it seems like it's simple to screw up also, here's a little script I wrote the other day to verify that all my reverse dns was setup correctly. I've written this script before at least twice, so I thought I would post it. Just feed it a CIDR range via command line and it will check all those ips. Like this:


# perl ptrchecker.pl 192.168.0.0/24


#!/usr/bin/perl


use NetAddr::IP;
use Socket;
use strict;

foreach my $cidr(@ARGV) {
    my $n = NetAddr::IP->new( $cidr );
    for my $ip( @{$n->hostenumref} ) {
      next if ($ip->addr() =~ /\.[0|1|2]5?5?$/);
      my ($name,$aliases,$addrtype,$length,@addrs) = gethostbyaddr($ip->aton(), AF_INET);
      my $addr = join ".", unpack('C4', (gethostbyname $name)[4]);
      print "busted ip: " . $ip->addr() . " PTR is $name, A is $addr\n" if ($ip->addr() ne $addr);
      #select(undef, undef, undef, 0.05); 
    }
}

Installing smartear on Ubuntu Jaunty

First apt-get remove pidgin. Don't do any autoremoving, you might need some of those devel packages later on. Next, hop on over to pidgin's and smartear's sites and download source tarballs.

Extract both tarballs, you will then need to compile pidgin from source. I did have to disable video and voice capabilites, that's fine for me. But if you want them you will need to find the correct libraries.

# apt-get -y remove pidgin
# apt-get -y build-dep pidgin
# ./configure --disable-vv
# make install

Now it's time to get into that SmartEar tarball. If you check out the INSTALL file you will see that you need to edit the Makefile and change the PIDGIN_SRCDIR to whatever directory you compiled pidgin in. So:

PIDGIN_SRCDIR=../whatever_directory_you_untared_to/pidgin

Then just run make install:

# make install

Done!