Today I accidentally changed permissions of all the files in some folder /usr/lib/git-core with the following command:

chmod o-rx *

At first I thought that I have broken my system, but in few minutes I remembered that I have the same distribution on some other machine, I listed the same folder on this machine and used the following commands to restore original permissions:

chmod o+rx *
find -maxdepth 1 -type f -perm 645 -exec chmod o-x {} \;

645 means the files that initially were -rw-r–r— and became -rw-r–r-x. This two commands saved me a lot of time. After that I even count the number of files with all permission combinations:

find -maxdepth 1 -type f -perm 644 | wc -l
find -maxdepth 1 -type f -perm 755 | wc -l
find -maxdepth 1 -type f -perm -o=x | wc -l

Ejabberd (Jabber daemon written in Erlang programming language) can be easily installed on Ubuntu 12.04 Server (Precise Pangolin) with the following command:

apt-get install ejabberd

The only steps needed to make Ejabberd work after the installation are to specify admin user and hostname in /etc/ejabberd/ejabberd.cfg file:

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
%% Options which are set by Debconf and managed by ucf

%% Admin user
{acl, admin, {user, "admin", "developernote.com"}}.

%% Hostname
{hosts, ["developernote.com"]}.

%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%

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Check your currently implemented firewall rules with the following command:

iptables -L

Examine the output. On a clean Ubuntu installation you will see an empty ruleset:

Chain INPUT (policy ACCEPT)
target     prot opt source               destination

Chain FORWARD (policy ACCEPT)
target     prot opt source               destination

Chain OUTPUT (policy ACCEPT)
target     prot opt source               destination

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Without going into particulars, it suffices to say that Ubuntu 12.04 has the following script that sets up encrypted swap:

ecryptfs-setup-swap

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