Configuring PostgreSQL to listen on all IPs

Tested on CentOS 6. Modify the line:

listen_addresses = '*'

In the /var/lib/pgsql/data/postgresql.conf file.

Setting root password on CentOS MySQL install

After installing and starting up mysqld run the following commands to set the root password:

# /usr/bin/mysqladmin -u root password '[password here]'
# /usr/bin/mysqladmin -u root -h [hostname here] password '[password here]'

Common SELinux problems and tasks

List current selinux context labels on files:

[root@machine1:/var/www/html]# ls -alZ
total 124K
drwxr-xr-x. root   root   system_u:object_r:httpd_sys_content_t:s0 ./
drwxr-xr-x. root   root   system_u:object_r:httpd_sys_content_t:s0 ../
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 administrator/
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 bin/
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 cache/
drwxr-xr-x. apache apache unconfined_u:object_r:httpd_sys_content_t:s0 cli/
...


Change the selinux context:

[root@machine1:/var/www/html]# chcon -Rv --type=httpd_sys_content_t ./*
changing security context of `./administrator/templates/hathor/less/forms.less'
changing security context of `./administrator/templates/hathor/less/buttons.less'
...


Enable Apache to make outbound database connections:

[root@machine1:/var/www/html]# setsebool -P httpd_can_network_connect=1

Enable Apache to use sendmail:

[root@machine1:/var/www/html]# setsebool httpd_can_sendmail 1

Finding the CWD (current working directory) of a running process

Luckily, due to the UNIX philosophy of "everything" is a file, makes it rather trivial to find what the current working directory is. You just need to look at the symbolic "cwd" link under the process directory:

# ls -al /proc/[process number here]/cwd lrwxrwxrwx 1 build build 0 Oct 18 12:29 /proc/2506/cwd /root/run

Gerrit and ActiveDirectory

We've recently started testing out Gerrit at work and one of the tasks when setting it up was to integrate the authentication with ActiveDirectory.

The process was fairly straight forward. For reference here is an example AD configuration:

[ldap]
 server = ldap://dc.company.org:389

 accountBase = ou=People,dc=company,dc=org
 accountPattern = (&(objectCategory=Person)(sAMAccountName=${username}))
 accountFullName = displayName
 accountEmailAddress = mail

 groupBase = ou=Groups,ou=People,dc=company,dc=org
 groupMemberPattern = (&(objectClass=group)(member=${dn}))

 username = cn=Gerrit User,ou=People,dc=company,dc=org
 password = ********

The username/password are for the "bind" user that will be used to query the server. More information can be found on the Gerrit auth documentation page.

Simple Perl and CGI example

This is probably the simplest possible example to get Perl working through cgi on Apache HTTPD. Instructions are for Ubuntu 12.04.

Install apache httpd:

sudo apt-get install apache2

Add the following "hello.pl" script to the /usr/lib/cgi-bin directory:

#!/usr/bin/perl

print "Content-type: text/html\n\n";
print "Hello World!";
exit;

Point your browser at http://localhost/cgi-bin/hello.pl and that's it!

etckeeper and bzr explorer

In my previous blog post, I talked about using the etckeeper package for keeping the entire /etc directory under version control. In this post I'll talk about how to manually audit the changes to see what changes were made and also how to reverse those changes, using the "bzr explorer" program.

To do this, we need to install the "bzr-explorer" package. Once this is done, you have to start up the GUI as the root user:

sudo bzr explorer

NOTE: I initially tried starting it up as a non-root user and it was not able to load the repository.

Once we've got this open, we can go to the "Open an existing location" pane and select the "Open" button. Navigate to the "/etc" directory and click on "Choose". This will load up the repository in the explorer window.

Now, if someone has modified a file under /etc but hasn't committed it, the screen will look like the following:

From here, we can see what the differences made were and also choose whether to commit the new version to the repository.

If we wanted to alternatively see a log of all of the changes that had been made, after opening the /etc repository, we could hit the "Log" button to bring up a listing of all of the commits. From there, selecting any particular commit would bring up a Diff screen showing the changes which had been made:

If we had seen a change which we didn't want and needed to roll back, right-clicking on any previous version and selecting "Revert" is enough to change the file back to it's previous state and update the repository.