Global users and groups are really useful for handing authentication and authorization at a global level, especially when interacting with things like Gerrit and other global services. Global users can also be used as service accounts within instances, between instances or between projects. There’s a number of downsides to global users though:

1. The global user creation process is laborious.
2. Global users must provide an email address.
3. Global users have a fixed home directory in /home (which is an autofs NFS or GlusterFS mount).
4. Global users can authenticate to all services, even if that’s not necessary or wanted.
5. Global users must have shell rights and must be added to a project to be properly usable for data access inside of a project.
6. Users get confused when told to create Labs accounts to be used as service accounts.
7. If multiple users want to access a global user, it’s necessary for the credentials to be shared, or to have a project admin create a sudo policy.
8. Global users don’t have personal groups, but instead have global groups, which are projects. Limiting access to data for a global user is difficult.

It’s also possible to define system users and groups via puppet and have those applied to instances within a project. There’s one major downside to this though: the changes would need to go through review first, which bottlenecks the process to the Operations team, and muddies up the puppet repository.

With the introduction of the Tools project, as a Toolserver replacement, there was a really strong need for service users and groups that could be handled in a simple way. Our Tools project implementer, Marc-Andre Pelletier, had a novel concept: per-project users and groups.

The concept and LDAP implementation

Marc’s initial concept was to have another set of OUs, like ou=project-people and ou=project-groups, where we’d create sub-OUs per project. We adjusted the concept when I showed Marc how we’re currently handling per-project sudo, though. Rather than using separate top-level OUs, we further extended the directory information tree (DIT) used by the OpenStack projects. Our OU for projects is ou=projects,dc=wikimedia,dc=org and the tools project OU is ou=tools,ou=projects,dc=wikimedia,dc=org. The extension for service groups also uses the sudo extension, and here’s the basic structure:

dn: cn=tools,ou=projects,dc=wikimedia,dc=org
objectClass: groupofnames
objectClass: extensibleobject
objectClass: top
cn: tools
info: servicegrouphomedirpattern=/data/project/%u
member: <member-list-goes-here>

# Single role, allowed to manage all project info
dn: cn=projectadmin,cn=tools,ou=projects,dc=wikimedia,dc=org
cn: projectadmin
roleOccupant: <member-list-goes-here>
objectClass: organizationalrole
objectClass: top

dn: ou=sudoers,cn=tools,ou=projects,dc=wikimedia,dc=org
ou: sudoers
objectClass: organizationalunit
objectClass: top

dn: ou=groups,cn=tools,ou=projects,dc=wikimedia,dc=org
ou: groups
objectClass: organizationalunit
objectClass: top

dn: ou=people,cn=tools,ou=projects,dc=wikimedia,dc=org
ou: people
objectClass: organizationalunit
objectClass: top

Note: for the project definition we have a pretty ugly hack. We’re sticking configuration information into the OU using the info attribute and extensibleobject. We’re doing this so that both cli tools and the web interface can know how to handle service groups. We should define our own schema and extend the object properly, but this was a quick and dirty hack for handling it to meet a hackathon deadline.

Allowing the addition of service groups is easy enough. When a service group is requested, a user and group are added to ou=people and ou=groups respectively. However, this doesn’t make the service groups easily accessible. To solve this, we automatically add a project sudo policy for every service group. Here’s a single service group added to the DIT:

dn: cn=local-example,ou=groups,cn=tools,ou=projects,dc=wikimedia,dc=org
objectClass: groupofnames
objectClass: posixgroup
objectClass: top
gidNumber: 100000
member: <member-list-goes-here>
cn: local-example

dn: uid=local-example,ou=people,cn=tools,ou=projects,dc=wikimedia,dc=org
objectClass: person
objectClass: shadowaccount
objectClass: posixaccount
objectClass: top
uid: local-example
cn: local-example
sn: local-example
loginShell: /usr/local/bin/sillyshell
homeDirectory: /data/project/example/
uidNumber: 100000
gidNumber: 100000

dn: cn=runas-local-example,ou=sudoers,cn=tools,ou=projects,dc=wikimedia,dc=org
sudoOption: !authenticate
objectClass: sudorole
objectClass: top
sudoRunAsUser: local-example
sudoCommand: ALL
sudoUser: %local-example
cn: runas-local-example
sudoHost: ALL

Project members can create service groups. The project member that creates the service group is the initial service group member. Members of the service group are allowed to add other members. All service group members can sudo to the service group without authentication.

The user and group have the same name, and the same uid/gid number. The uid and gid range were meant to be reserved and be allowed to overlap with service groups in other projects. Similarly, the user and group names were prefixed with local- and were to be allowed to overlap with service groups in other projects. The uid/gid range and non-unique user/group names design has changed since initial implementation, but I’ll get into that later.

The instance implementation

We’re using nslcd, which has support for defining multiple OUs for available services (passwd, shadow, group, etc.). To make service groups available on instances in a project, we use a similar approach as per-project sudo. Puppet has a variable defined for the OpenStack project, which is then used when adding the service group specific OUs to nslcd.conf:

# root
base dc=wikimedia,dc=org

# Global users and groups
base passwd ou=people,dc=wikimedia,dc=org
base shadow ou=people,dc=wikimedia,dc=org
base group ou=groups,dc=wikimedia,dc=org

# Per-project users and groups (service groups)
base passwd ou=people,cn=tools,ou=projects,dc=wikimedia,dc=org
base shadow ou=people,cn=tools,ou=projects,dc=wikimedia,dc=org
base group ou=groups,cn=tools,ou=projects,dc=wikimedia,dc=org

That there’s a pretty massive gotcha here: if any of the OUs don’t exist for a service, it breaks the entire service. It’s very important that the OUs exist for all projects in which this will be used.

After-implementation changes and further changes to come

We added service groups prior to the tools project ramp-up, which was in April 2013. Since then we’ve made some modifications from the original design.

The first issue we ran into was with non-globally-unique uids and gids. Users can have a large number of groups, due to multiple project membership and service group membership. We’re providing per-project NFS shares, and NFS has a 16 group limitation defined in its RFC. A way around this is to use the –manage-gids option in rpc.mountd. With manage-gids, the NFS server does the secondary group lookup and ignores whatever the client sends to it. Here’s where the problem with non-unique uids and gids comes in. The server needs to know about all groups in all projects. We sync group info from LDAP into the NFS server’s local groups file, and we can name the groups whatever we want, but for multi-tenancy purposes the uids and gids need to be unique. Also, in general, making the uids and gids unique makes it easier to integrate other services that aren’t natively multi-tenant.

The second issue is with non-unique service group names. It’s easier to integrate service groups into services that aren’t natively multi-tenant if the service group names are unique as well. We’ll be changing the naming scheme from being prefixed with local- to being prefixed with <projectname>- or some variant of that. We have a specific use case in mind, using Gerrit, for this change, but I’ll write a follow-up post about that.

So, what’s new with the wiki?

1. All articles now have discussion pages
2. It’s possible to make PDFs out of individual pages or to create a book (as a PDF or an actual physical book) from collections of articles
3. Uploads are global and can be used in multiple articles
4. Templates can be written using Lua
5. Gadgets can be written using Javascript and CSS and shared with all wiki users
6. Layout of articles can use Twitter’s Bootstrap, thanks to the strapping-mediawiki skin
7. There’s a mobile view, though mobile device detection won’t be enabled until next Wikimedia branch-point release (1-2 weeks)
8. Many more features available in MediaWiki that don’t exist in MoinMoin

Let me know if there’s any issues you run into with the new wiki.

1. Continue with the Labs project. Finish set up of test/dev Labs, and begin work and make major progress on tool Labs.
   • Partial success: Test/dev Labs is going really well. At the time of this writing we have 99 projects, 174 instances, and 446 users. We have per-project nagios, ganglia, puppet, and sudo. We also have an all-in-one MediaWiki puppet configuration. We currently have one zone with 5 compute nodes, and will mostly triple the capacity of that in the next month. We have another zone coming up in another datacenter that will be 8 large compute nodes. Stability is still currently a concern, and we haven’t come out of closed beta, yet, though. Also, work on Tool Labs is mostly not started. We do have a bots cluster that’s community managed, but we don’t have database replication and don’t have a simple way for tool authors to contribute.
2. Hire a devops contractor for work on Labs.
   • Success: Not only did we hire a devops contractor, we built a larger team. We now have Andrew Bogott (developer), Sara Smollett (operations), Faidon Liambotis (operations) and myself (operations).
3. Build a devops community around the Wikimedia architecture.
   • Success: We had roughly 700 changes pushed into the operations/puppet repository from people who are not operations team members. A number of our larger Labs projects were built by volunteers (bots, deployment-prep, nagios, for instance). Volunteers are members of most of the projects that exist in Labs.
4. Finish the HTTPS project. This will hopefully be complete from the ops perspective by the end of this year.
   • Partial success: HTTPS is fully enabled on all sites, for both IPv4 and IPv6. I’ve listed this as a partial success, because I’d like the default for logged-in users to be HTTPS. Also, I wanted secure.wikimedia.org to redirect properly to HTTPS by now, and haven’t found time to do so.
5. On-board new employees.
   • Success: We brought on a lot of new Operations Engineers last year and I helped on-board nearly all of them. That said, I wish I would have written more documentation on the process as I was doing it.
6. Enable OpenID as a provider and oAuth on Wikimedia (this goal still needs consensus).
   • Partial failure, again: That said, I’ve been pushing for oAuth very strongly internally and it looks like this is now a stated goal of next year! oAuth is crucial to the success of Labs, so I’m very happy this is happening.

What did I accomplish that was outside of my stated goals?

1. Installed Gerrit, moved our operations repositories from SVN to Git and released our puppet repository as open source and cloneable to the world.
2. Assisted the core services team with the migration from SVN to Git.
3. Launched Labs (in October 2011 at the New Orleans MediaWiki hackathon).
4. Wrote the OpenStackManager and OATHAuth MediaWiki extensions.
5. Massively refactored the LdapAuthentication MediaWiki extension.
6. Rewrote a couple IRC bots (ircecho and adminbot).
7. Wrote a new deployment system that may replace our production deployment system.
8. Did the operations portion of the SOPA blackout.
9. Organized the New Orleans MediaWiki hackathon.
10. Organized an OpenStack meetup held at the Wikimedia Foundation offices.
11. Pushed 790 changes into Gerrit.
12. Made 1,100 edits to labsconsole (those edits include project creations, modification of projects, creation/deletion of instances and actual writing of documentation).
13. Got the 100,000th revision in Wikimedia SVN, much to the dismay of others!

What are my goals for next year?

1. Stabilize Labs.
2. Add a second Labs zone in eqiad.
3. Make major progress on Tool Labs.
4. Add a real queue to the Wikimedia infrastructure, for jobs and other needs.
5. Continue building a solid community around Labs.
6. Continue to improve the HTTPS infrastructure.

OATHAuth is an opt-in feature that adds more security accounts in a wiki. It provides two-factor authentication, using your phone as the something you have, and your username/password as the something you know. If you are using iPhone or Android, you can use the Google Authenticator app as a client. There are also clients for most other phones and desktops; Wikipedia has a good list of clients.

If you have an account in Wikimedia Labs, you can enable two-factor authentication via the sidebar now.

As of version 0.1, OATHAuth only works when chained with LDAPAuthentication. Version 0.2 will work in a standalone manner. See the following image gallery for how it’s used:

In the original design, being a project member in specific projects would automatically give you root via sudo and being a project member in a global project would give you shell, but not root. We were handling this through puppet configuration. This was a fairly limiting system. Giving fine grained permissions wasn’t easy. The instances knew which users were a member of a project since the projects were also posix groups; however, they didn’t know which users were in the roles of that project, so there was no fined grained way to handle this.

sudo-ldap to the rescue. With sudo-ldap, we can manage sudo policies in LDAP, and those can be done in a per-project basis. Let me explain how we’re handling this while also ensuring the original assumed design still applies to old projects.

Handling the sudo policies in LDAP

To make sudo work per-project, we need to make a sudoers OU for each project. Projects are located at ou=projects,dc=wikimedia,dc=org. We have an example project at cn=testproject,ou=projects,dc=wikimedia,dc=org. We can create a new sudoers OU for this project, with a default policy (for backwards compatibility):

dn: ou=sudoers,cn=testproject,ou=projects,dc=wikimedia,dc=org
ou: sudoers
objectclass: organizationalunit
objectclass: top

dn: cn=default,ou=sudoers,cn=testproject,ou=projects,dc=wikimedia,dc=org
cn: default
objectClass: sudorole
objectClass: top
sudoCommand: ALL
sudoHost: ALL
sudoUser: ALL

The above creates a sudoers OU underneath the project’s object and creates a default policy for that project that gives all users the ability to run all commands via sudo.

For every pre-existing specific project, I created an OU and a default policy, then for every pre-existing global project I only created the OU, ensuring everything continued working how things worked in the original design. Whenever a project is created the OU and a default policy is also now automatically created with the project.

Configuring sudo on the instances

Now we must configure the instances to pull their sudo policies from this OU. Here’s the puppet template we’re using for /etc/sudo-ldap.conf:

BASE            <%= basedn %>
URI             <% servernames.each do |servername| -%>ldap://<%= servername %>:389 <% end -%>

BINDDN          cn=proxyagent,ou=profile,<%= basedn %>
BINDPW          <%= proxypass %>
SSL             start_tls
TLS_CHECKPEER   yes
TLS_REQCERT     demand
TLS_CACERTDIR   /etc/ssl/certs
TLS_CACERTFILE  /etc/ssl/certs/<%= ldap_ca %>
TLS_CACERT      /etc/ssl/certs/<%= ldap_ca %>
<% if ldapincludes.include?('sudo') then %>SUDOERS_BASE    <%= sudobasedn %><% end %>

The sudobasedn variable is being set as this:

$sudobasedn = "ou=sudoers,cn=${instanceproject},ou=projects,${basedn}"

For a more in-context view, you can clone our repo, or browse it via gitweb.

Managing the sudo policies

In the trunk version of the OpenStackManager extension, I’ve added support for managing per-project sudo. Users must be a member of the sysadmin role to do so.

This release is mostly aimed at performance and usability. Here’s a list of changes:

• Added a project filter. Rather than showing all projects, only projects selected in the project filter will show in the management interfaces. This should make the interfaces contain far less text, and should make interfaces load much faster.
• Refactored the list pages so that styles can be applied to all pages easily. Applied a couple CSS styles globally across all of the pages. For instance, the table text has been changed to be top aligned, to make large tables easier to handle.
• Merged in Platonides’s change for handling SSH keys uploaded in formats other than OpenSSH format. Keys in non-OpenSSH format will automatically be converted, if possible. If a private key, or a key in a bad formatted is uploaded, it’ll be rejected.
• Changed the project section collapsing behavior. Rather than the project title collapsing the project’s section, a “Toggle” action will do so. The project name has been changed back to being a link to the project’s page.
• Projects are now sorted alphabetically everywhere.
• Various fixes related to the PHP aws-sdk.
• Move creation forms to list pages for many management pages, to avoid extra clicks where possible.
• Various memcache support additions and fixes.
• Added a fix to allow user creation through MediaWiki interface.

If you’d like to help develop this extension, I’ve created a development environment in a project in Wikimedia Labs. Find me on #wikimedia-labs on Freenode or email me to get a labs account and access to the project.

I’ve been busy enough lately working on our OpenStack infrastructure that I haven’t made an OpenStackManager release in a while. Over the past seven months I’ve continued to make small changes to the software, and the past few weeks I’ve added features I feel deserve another release.

This is a bugfix and features release. Major changes include compatibility for cactus and diablo releases of nova, and 1.18 compatibility for MediaWiki. The changes in this release focused mainly on making workflow easier. Here’s a complete list of changes:

• Added a reboot action for instances
• Made compatibility changes for cactus and diablo nova releases
• Made compatibility changes for MediaWiki 1.18
• Added support for configurable naming attributes
• Added support for adding objectclasses and attributes for users that are missing them
• It’s now possible for MediaWiki to no longer have to create users, only update select user attributes and objectclasses
• Made a bunch of bugfixes regarding security groups
• Added support for wildcard DNS entries
• Added realm and instancename variables to puppet default variables, so that they can be used in puppet runs
• Added support for wiki page creation for Projects
• Added support for configuring default images for instances
• Added support for creating server admin logs per project
• Added support for default security group rules on project creation
• Added dialog to project creation for adding members to projects and roles upon creation
• Added support for managing puppet classes and variables through the interface, rather than LocalSettings.php
• Made a usability change to instance creation: the default security group will always be selected by default
• Added support for including the ssh key fingerprint of an instance in the “your instance is ready” emails
• Made a usability change to only show actions to users if they can perform them
• Lots of other minor bug fixes
• Bugfixes from John Du Hart, Sam Reed and Mark Hershberger

If you’d like to help develop this extension, I’ve created a development environment in a project in Wikimedia Labs. Find me on #wikimedia-labs on Freenode or email me to get a labs account and access to the project.

1. Create an instance and use it to do experimentation with the service.
2. Document the service, along with the installation process on wikitech, after ensuring the service is working properly.
3. Create a second instance. Following the documentation written, puppetize the service.
4. Create a third instance. Ensure the puppetized service runs properly when initialized from scratch.
5. Kill all three instances, and replace the instances in the test cluster.

When a service changes in puppet, follow the above cycle as well.

Using this process, I can be assured the puppet manifests, as written, will allow me to repeatedly install this service.

The problem with NFS home directories, however, is that they are fairly insecure. They can be used between instances to escalate privileges. In our environment, this isn’t a problem for instances within a project. If a user is a member of a project, they have shell on all instances. If they are given sudo access in a project, they are given sudo access on all instances. Between projects, however, is a problem. user-A with root on instance-A in project-A could su to to user-B on instance-A, modify the user’s authorized_keys file, and then have access to project-B if home directories are shared across projects.

To avoid cross-project escalation, each project needs its own set of home directories. This means we can’t simply export /home to the instance’s private network and be done with it. We’ll need to create an exports file, and share different directory trees with specific instances. We’ll also need to mount home directories differently on the instances, depending on the project they belong to.

To do so, we’ll use a combination of puppet, LDAP, autofs, and Nova.

Creating the exports file

To create the exports file we need three things:

1. A list of projects
2. A list of instances within each project
3. A list of home directory locations for each project

The first two can be found via LDAP. The query for a list of projects is: ‘(&(objectclass=groupofnames)(owner=*))’. The query for a list of instances within each project is: ‘(puppervar=instanceproject=<project>)’. Of course, this approach is only usable for people using the OpenStackManager extension for MediaWiki; I’ll mention more portable ways to get this information later in the post.

The third we can extrapolate, we just need a base directory. I chose to use /export/home/<project> for the locations.

I wrote a python script that will pull this information, and create an exports file that looks like this:

/export/home/<project1> <project1-instance1>(rw,no_subtree_check) <project-instance2>(rw,no_subtree_check) <project_instance...>(rw,no_subtree_check)
/export/home/<project2> <project2-instance1>(rw,no_subtree_check) <project2-instance2>(rw,no_subtree_check) <project2_instance...>(rw,no_subtree_check)

Mounting the shares from the instances

Each instance needs to mount the share, depending on its project. There’s a number of ways we can do this, but I like the flexibility of using autofs and LDAP to manage NFS mounts. To add slightly more flexibility we’ll involve the help of puppet as well.

In LDAP, we can create autofs entries by making maps and objects. The following objects add support for /home:

dn: nisMapName=auto.master,<basedn>
objectClass: top
objectClass: nisMap
nisMapName: auto.master

dn: nisMapName=auto.home,<basedn>
objectClass: top
objectClass: nisMap
nisMapName: auto.home

dn: nisMapName=/home,nisMapName=auto.master,<basedn>
objectClass: top
objectClass: nisObject
cn: /home
nisMapEntry: ldap:nisMapName=auto.home,<basedn>
nisMapName: auto.master

We also need to add entries for the specific home directories. Here we are going to invoke a little awesome magic that autofs has: variables. Here’s the entry we are using for all home directories in all projects:

dn: cn=*,nisMapName=auto.home,<basedn>
changetype: add
nisMapEntry: ${SERVNAME}:${HOMEDIRLOC}/&
objectClass: nisObject
objectClass: top
nisMapName: auto.home
cn: *

We only need the one entry, which saves us from having to create and delete entries on creation and deletion of projects. Using this, however, means we need to set the variables. This is where puppet comes in. First, though, let’s look at the node in LDAP:

dn: dc=i-0000005c,dc=pmtpa,ou=hosts,dc=wikimedia,dc=org
objectClass: domainrelatedobject
objectClass: dnsdomain
objectClass: domain
objectClass: puppetclient
objectClass: dcobject
objectClass: top
puppetVar: realm=labs
puppetVar: writable=false
puppetVar: db_cluster=s1
puppetVar: instancecreator_email=rlane@wikimedia.org
puppetVar: instancecreator_username=Ryan Lane
puppetVar: instancecreator_lang=en
puppetVar: instanceproject=testlabs
puppetClass: base
puppetClass: ldap::client::wmf-test-cluster
puppetClass: exim::simple-mail-sender
puppetClass: db::core
puppetClass: mysql::mysqluser
puppetClass: mysql::datadirs
puppetClass: mysql::conf
l: pmtpa
associatedDomain: i-0000005c.pmtpa.wmflabs
associatedDomain: labs-db2.pmtpa.wmflabs
dc: i-0000005c
aRecord: 10.4.0.12

All the above objectclasses and attributes are available for use in puppet. The really important one here is instanceproject=testlabs.

We can set the autofs variables via the OPTIONS variable in the /etc/default/autofs file:

OPTIONS=”-DSERVNAME=<%= nfs_server_name %> -DHOMEDIRLOC=<%= homedir_location %>”

Here SERVNAME and HOMEDIRLOC autofs variables are being set. nfs_server_name and homedir_location are being set via a puppet template. Both are being determined via a manifest:

$homedir_location = "/export/home/${instanceproject}"

nfs_server_name is a hash, based on the project:

$nfs_server_name = $instanceproject ? {
	default => "labs-nfs1",
}

I chose to use a hash based on project so that I can choose to separate the server based on project as well, if needed for performance, or extra security.

Managing user home directories

Everything up to this point is just creating the shares. However, we must maintain the users’ home directories as well. For this, we need to know which users are in which projects, and we need to manage their home directories per project.

I wrote a script to search for users, based on a group (the project), that selectively creates/deletes/renames home directories and authorized_keys files. I should note here that I don’t use nova’s mechanisms for SSH key management, as it isn’t portable between applications. I instead store the keys in the user’s LDAP entry.

There’s a security issue with management of home directories. If a user is added to a project and we create a home directory, with a populated authorized_keys file, then remove the user from the project, but don’t remove their home directory, the user will still have access to the project’s instances. There’s two ways I go about solving this issue:

1. Ensure the user only has access to the instance if they are in the project, using access.conf. In my architecture, when projects are added, they are also made a posixgroup, with a gid. Thanks to this, we can treat the project as a system group in all instances. In access.conf we limit access to the project group.
2. User’s home directories are moved from /export/home/<project>/<user> to /export/home/<project>/SAVE/<user> when they are removed from the project.

Problems with this solution, and future improvements to make

The major shortcoming of this solution is that it isn’t terribly portable. It is dependent on using LDAP, and storing specific information in the LDAP directory. Using the nova tools, or having nova manage the exports on instance creation/deletion would make this a much more portable solution.

Another shortcoming is that it isn’t terribly scalable. The exports file is being created from scratch every single script run (which needs to happen fairly frequently). Ideally, nova would write to a queue, and the NFS instance would add/remove instances from the exports as instances are created/deleted.

Thankfully, I didn’t have a shortage of ideas about how to accomplish this, as shown in my proposal. I decided upon the quick and dirty approach, opting to do one of the more reusable approaches later. I’ll likely add support to nova for this at some time in the future.

Our puppet configuration is broken into two environments (production and labs), each environment having a public and private repository. Inside of these repositories our configuration is broken into three main directories: files, templates, manifests. I often jump between repositories, directories within repositories, and branches within different screen windows.

The information I need to know is this:

• The current working directory in each screen window
• When inside a repository, which branch is active
• Whether the branch has modifications or not

Using a combination of screen and bash configuration, I display the current working directory as the title for each screen window. Here’s the bash configuration for this (in .bashrc):

export PROMPT_COMMAND='
if [ $TERM = "screen" ]; then
 MYPWD="${PWD/#$HOME/~}"
 [ ${#MYPWD} -gt 20 ] && MYPWD=..${MYPWD:${#MYPWD}-18}
 echo -n -e "\033k$MYPWD\033\\"
fi
'

Here’s the screen configuration for this (in .screenrc):

hardstatus alwayslastline
hardstatus string "%{.bW}%-w%{.rW}%n %1`%{-}%+w %=%{..G} %H %{..Y} %m/%d %C%a "

Thanks to Vishvanada Ishava, I can tell which branch is active, and whether or not there are modifications in the repository I’m in. Here’s the bash configuration for this (in .bashrc):

function git_branch {
  git branch --no-color 2> /dev/null | egrep '^\*' | sed -e 's/^* //'
}
function git_dirty {
  # only tracks modifications, not unknown files needing adds
    if [ -z "`git status -s | awk '{print $1}' | grep '[ADMTU]'`" ] ; then
        return 1
    else
        return 0
    fi
}

function dirty_git_prompt {
    branch=`git_branch`
    if [ -z "${branch}" ] ; then
        return
    fi
    git_dirty && echo " (${branch})"
}

function clean_git_prompt {
    branch=`git_branch`
    if [ -z "${branch}" ] ; then
        return
    fi
    git_dirty || echo " (${branch})"
}

export PS1='\n\e[1m\u\e[m@\e[4m\h\e[m:\e[7m\w\e[m\[\033[01;31m\]$(dirty_git_prompt)\[\033[01;32m\]$(clean_git_prompt)\[\033[00m\]\n\# \$> '

Here’s a screenshot of what it looks like (and, yes, the name of my laptop is Free-Public-Wifi :D):