Sometimes we have to calculate networks. We are interested in stuff like: networkid, subnetmask, min. hostip, max. hostip, how many hosts can we address in this network aso.. There are many tools for calculating networks. And they are perfectly good. If you need it in a c programm, there are libraries for that too. But I think it's not neccessary to use libraries for that. If you calculate it manually, it's just a matter of working with bits in a 32bit address, so it might be a quite easy task...
On this page is a list of howto-disable-sslv3-support on different Servers.
Here is a very nice article about hardening encryption for ssh-connections
DNS-Blacklist AHBL recently stopped their services. Since that I had many problems with our spamfilters. They are still using this blacklist and give all the mails a higher score because AHBL doesn't exist anymore.
The following entry in /etc/spamassassin/local.cf solvesthe problem(quick fix) :
score DNS_FROM_AHBL_RHSBL 0
Sometimes it is useful to compare to directories and display the differences. diff can do the trick for you
diff -r dir1/ dir2/
If you just want a overview about the differences then just use "brief":
diff --brief -r dir1/ dir2/
git can show you the differences too, and it can do it colorful if you want
git diff dir1/ dir2/
If you accidently deleted a text-file, you might be able to recover it using grep:
$ grep --binary-files=text --context=x 'stringfromyourfile' \ /dev/whateverPartition > someFile.txt
x are the lines before and after the string.
I found this idea on this blog.
Today I upgraded Thunderbird and then my SSL-connections to postfix did not work. In /var/log/mail.log i found the following:
SSL3_READ_BYTES:tlsv1 alert unknown ca:s3_pkt.c:1258:SSL alert number 48:
After a while i found this solutionsJust change the following thunderbird-setting:
security.use_mozillapkix_verification to false
Geeky christmas greetings...
If you have thousands of emails in your mailbox, the fastest way to delete them all is by open the maildir in mutt( mutt -f MAILDIR ) and do the following:
D(shift+d) and then: ~s .*