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How to write LCFG components for EDG
Updated 9/2002
[email protected]
German Cancio – WP4-install LCFG HOW-TO - n° 1
Overview
•LCFG – short reminder
Slides stolen from Enrico and Massimo / INFN
•Writing Components for EDG usage
•Outlook: LCFGng and => release 2
•Documentation and links
German Cancio – WP4-install LCFG HOW-TO - n° 2
LCFG – short reminder
German Cancio – WP4-install LCFG HOW-TO - n° 3
WP4 & LCFG
u LCFG
is originally developed by the Computer Science Department
of Edinburgh University
u Handles
automated installation, configuration and management of
machines
u Basic
n
n
n
n
features:
automatic installation of O.S.
installation/upgrade/removal of all (rpm-based) software packages
centralized configuration and management of machines
extendible to configure and manage custom application software
German Cancio – WP4-install LCFG HOW-TO - n° 4
LCFG diagram
Config files
LCFG Config Files
+inet.services telnet login ftp
+inet.services telnet login ftp
+inet.allow
telnet login ftp sshd
+inet.allow
telnet login ftp sshd
+inet.allow_telnet ALLOWED_NETWORKS
+inet.allow_telnet
ALLOWED_NETWORKS
Read
Load
+inet.allow_login
ALLOWED_NETWORKS
rdxprof
ldxprof
+inet.allow_login
Profile
ALLOWED_NETWORKS
Profile
+inet.allow_ftp
ALLOWED_NETWORKS
<inet>
+inet.allow_ftp
ALLOWED_NETWORKS
<inet>
+inet.allow_sshd
ALL
<allow
cfg:template="allow_$
tag_$ daemon_$">
+inet.allow_sshd
ALL
<allow
cfg:template="allow_$
Profile
tag_$
Genericdaemon_$">
+inet.daemon_sshd
yes
<allow_RECORD
cfg:name="telnet">
+inet.daemon_sshd
yes
Object
Component
<allow_RECORD
cfg:name="telnet">
.....
<allow>192.168., 192.135.30.</allow>
.....
<allow>192.168., 192.135.30.</allow>
+auth.users
myckey
</allow_RECORD>
+auth.users
myckey
</allow_RECORD>
Local cache /home/mickey
+auth.userhome_mickey
.....
+auth.userhome_mickey
inet/home/mickey
auth
.....
+auth.usershell_mickey
/bin/tcsh
LCFG
Objects
</auth>
+auth.usershell_mickey /bin/tcsh
</auth>
<user_RECORD cfg:name="mickey">
<user_RECORD cfg:name="mickey">
<userhome>/home/MickeyMouseHome</userhome>
<userhome>/home/MickeyMouseHome</userhome>
<usershell>/bin/tcsh</usershell>
<usershell>/bin/tcsh</usershell>
</user_RECORD>
</user_RECORD>
XML profiles
HTTP
/etc/shadow
/etc/services
/etc/shadow
/etc/services
/etc/group
/etc/inetd.conf
/etc/group
/etc/inetd.conf
Make XML
Profile
/etc/passwd
/etc/hosts.allow
/etc/passwd
/etc/hosts.allow
....
in.telnetd : 192.168., 192.135.30.
....
in.telnetd : 192.168., 192.135.30.
mickey:x:999:20::/home/Mickey:/bin/tcsh
in.rlogind : 192.168., 192.135.30.
mickey:x:999:20::/home/Mickey:/bin/tcsh
in.rlogind : 192.168., 192.135.30.
....
in.ftpd : 192.168., 192.135.30.
....
in.ftpd : 192.168., 192.135.30.
sshd : ALL
sshd : ALL
Server
Abstract configuration
parameters for all nodes
stored in a central
repository
Web Server
XML Profile
Client nodes
A collection of agents read
configuration parameters and either
generate traditional config files or
directly manipulate various services
German Cancio – WP4-install LCFG HOW-TO - n° 5
LCFG configuration (I)
u Most
of the configuration data are common for a category of nodes
(e.g. diskservers, computing nodes) and only a few are node-specific
(e.g. hostname, IP-address)
u Using
the cpp preprocessor it is possible to build a hierarchical
structure of config files containing directives like #define,
#include, #ifdef, comments with /* */, etc...
u The
configuration of a typical LCFG node looks like this:
#define HOSTNAME pc239
/* Host specific definitions */
#include "site.h"
/* Site specific definitions */
#include "linuxdef.h"
/* Common linux resources */
#include "client.h"
/* LCFG client specific resources */
German Cancio – WP4-install LCFG HOW-TO - n° 6
LCFG configuration (II)
From "site.h"
#define LCFGSRV
grid01
#define URL_SERVER_CONFIG
http://grid01/lcfg
#define LOCALDOMAIN
.lnl.infn.it
#define DEFAULT_NAMESERVERS
192.135.30.245
[...]
From "linuxdef.h"
update.interfaces
eth0
update.hostname_eth0
HOSTNAME
update.netmask_eth0
NETMASK
[...]
From "client.h"
update.disks
hda
update.partitions_hda
hda1 hda2
update.pdetails_hda1
free /
update.pdetails_hda2
128 swap
auth.users
mickey
auth.usercomment_mickey
Mickey Mouse
auth.userhome_mickey
/home/Mickey
[...]
German Cancio – WP4-install LCFG HOW-TO - n° 7
LCFG: configuration changes
u Server-side:
when the config files are modified, a tool (mkxprof)
recreates the new xml profile for all the nodes affected by the
changes
n
n
this can be done manually or with a daemon periodically checking for
config changes and calling mkxprof
mkxprof can notify via UDP the nodes affected by the changes
u Client-side:
the server
n
n
another tool (rdxprof) downloads the new profile from
usually activated by an LCFG component at boot
can be configured to work as
s
daemon periodically polling the server
s
daemon waiting for notifications
s
started by cron at predefined times
German Cancio – WP4-install LCFG HOW-TO - n° 8
LCFG components for EDG usage
German Cancio – WP4-install LCFG HOW-TO - n° 9
LCFG: what’s a component?
u Component
u It's
== object
a simple shell script (but in LCFGng it can be a perl script)
u Each
component provides a number of “methods” (start, stop,
reconfig,...) which are invoked at appropriate times
uA
simple and typical object behaviour:
n
n
n
Started when notified of a configuration change
Loads its configuration (locally cached)
Configures the appropriate services, by translating config parameters
into a traditional config file and reloading a service if necessary (e.g.
restarting a init.d service).
German Cancio – WP4-install LCFG HOW-TO - n° 10
LCFG: custom components
u LCFG
provides components to manage the configuration of services
of a machine: inet, auth, nfs, cron, ...
u Admins
can build new custom components to configure and manage
their own applications:
n
n
n
define your custom “resources” (configuration parameters)
Write a script containing standard methods with your custom code.
Include in your script a generic library, which contains the definition of
common function used by all components (config loading, log, output, ...)
u For
simple components usually just a few lines of code
German Cancio – WP4-install LCFG HOW-TO - n° 11
Writing LCFG components for EDG
u Software
written for EDG should be portable to whatever farm
management system is used.
u It
is therefore recommended to use whenever possible, standard
SysV procedures for managing services: init.d scripts and
chkconfig.
u LCFG
should not be used for replacing existing SysV init.d
functionality!
u LCFG
n
n
n
should be used for
retrieving configuration information from the CDB and recreate local
config files
Restarting services if needed via init.d scripts (restart/reload)
Enabling/disabling SysV services to match the configuration DB’s
contents (using chkconfig)
German Cancio – WP4-install LCFG HOW-TO - n° 12
LCFG component methods for EDG
Methods to implement:
Reconfigures the service and notifies running
processes. The most important method for EDG usage.
u Configure():
‘starts’ the component. Should only call Configure()
for EDG usage.
u Start():
u Methods
n
n
not recommended for EDG:
Stop(), Run(), Suspend(), Resume(), Lock(), Query()
Doc(): use a .pod file instead.
German Cancio – WP4-install LCFG HOW-TO - n° 13
EDG / LCFG component template (I)
#!/bin/bash2
class=mycomp # set the name of the component (mycomp)
. /etc/obj/generic # include std methods and definitions
# Start the component
Start() {
}
# Do the configuration
Configure() {
}
# 'main' program
Case “$1” in
configure)
Configure;;
*)
DoMethod “$@”;;
esac
German Cancio – WP4-install LCFG HOW-TO - n° 14
LCFG component template (II)
u Start()
method:
# ‘Start’ the component
Start() {
Generic_Start; # standard setup steps
Configure; # reconfigure the component
if [ $? = 0 ]; then
OK "Component mycomp started"
else
Fail "Starting component mycomp"
fi
}
German Cancio – WP4-install LCFG HOW-TO - n° 15
LCFG component template (III)
u Configure()
method:
# Do the configuration
Configure() {
LoadResources
myresource1 myresource2 …
CheckResources myresource1 myresource2 …
# your code
do_whatever …
return status;
}
German Cancio – WP4-install LCFG HOW-TO - n° 16
LCFG component template (IV)
u The
specific part in the configure() method will usually contain
three steps:
# 1. Load myconfig resource as environment variable
LoadResources myconfig
CheckResources myconfig
# 2. Generate (or update) config file
sed –e “s%MYCONFIG%$myconfig%” \
/etc/obj/conf/myconfigtemplate > /etc/myconfig
# 3. Reload/restart a service if neccessary
/etc/rc.d/init.d/myservice reload
German Cancio – WP4-install LCFG HOW-TO - n° 17
EDG relevant built-in standard functions
u LoadResources
the environment
resource1 resource2 …: loads resources into
resource1 resource2 …: checks that
resources are defined in the environment, fails otherwise
u CheckResources
u Fail
string: prints out a [FAIL] message and exits ($? = 1)
u Warn
string: prints out [WARNING] message
u OK
string: prints out [OK] message
u LogMessage
string: Adds message to logfile
(see also the /etc/obj/generic file)
German Cancio – WP4-install LCFG HOW-TO - n° 18
Configuration information (I)
Configuration information is stored on the LCFG server in two types of
files:
1. The resource definition files (.def)
2. The normal .h & machine configuration files.
German Cancio – WP4-install LCFG HOW-TO - n° 19
Configuration information (II)
1. The .def files contain default resource information:
mycomp.def
# component name
class mycomp
# implemented methods
methods start configure
# defined resources and defaults
myconfig1
myconfig2
defaultvalue2
German Cancio – WP4-install LCFG HOW-TO - n° 20
Configuration information (III)
2. The normal .h & machine config files, where the default configuration is
enhanced/overwritten:
mycomponent.<resource>
<value>
mycomp.myconfig1
whatevervalue
mycomp.myconfig2
whateverothervalue
Some special resources have to be declared for including a component to be
deployed:
# add to profile (always needed)
EXTRA(profile.components)
mycomp
# start on boot time (if required)
EXTRA(boot.services)
mycomp
# method to call on runtime config changes (if required)
profile.reconfig_mycomp
configure
German Cancio – WP4-install LCFG HOW-TO - n° 21
More complex configurations
u Sometimes,
key-value pairs are not sufficient for the required
configurations.
n
For example: arrays or lists
u LCFG
has a mechanism for mapping hierarchical structures into keyvalue pairs…
u Table
with person names, ages, and phone numbers (.def file)
@persons age_$ phone_$
persons
age_$
phone_$
German Cancio – WP4-install LCFG HOW-TO - n° 22
More complex configurations (II)
Now we want to add the following to the node config:
u John,
35, 12346 and Phil, 21, 54321
The node config file will look like:
mycomp.persons
John Phil
mycomp.age_John
35
mycomp.phone_John
12346
mycomp.age_Phil
21
mycomp.phone_Phil
54321
The persons, age_John, phone_John, age_Phil, phone_Phil
resources will be accessible as environment variables as any other resource.
German Cancio – WP4-install LCFG HOW-TO - n° 23
More complex configurations (III)
The component accessing the info needs to do:
LoadResources persons
for i in $persons ; do
LoadResources age_$i phone_$i
agehlp=age_$i ; age=${!agehlp}
phonehlp=phone_$i ; phone=${!phonehlp}
echo name: $i – age: $age – phone: $phone ;
done
(using bash2 semantics)
German Cancio – WP4-install LCFG HOW-TO - n° 24
More complex configurations (IV)
u Note
that there is no limit in the nesting of resources (lists of lists
are possible as well as lists of lists of lists)
n
n
There are some examples (obj-update)
However it is complex to handle in the current production testbed LCFG.
German Cancio – WP4-install LCFG HOW-TO - n° 25
Some tipps
u Avoid
dumping configuration files literally into the database
@configlines
configline_$
configlines
01 02 03 04 05 …
configline_01
FARM=MOOH_BAR
configline_02
MILK_NODE=COW_001
...
u This
leads to some problems, eg. when you overwrite values for host specific
values
n
How do you know that configline_324 is still the line you wanted to change?
u Rather
n
n
use a template configuration file shipped with the component RPM
Substitute relevant entries in the template cf file
With LCFGng (release 1.3) you can use a built-in template processor for this.
u Keep
explicit configuration information in the LCFG config files.
German Cancio – WP4-install LCFG HOW-TO - n° 26
Example
ldconf - Configures /etc/ld.so.conf (Cal Loomis)
.def file:
class
ldconf
methods
start configure
conffile
paths
Resources defined on server:
conffile
/etc/ld.so.conf
paths
/usr/local/lib /opt/globus/lib
German Cancio – WP4-install LCFG HOW-TO - n° 27
Example (II)
Component: Configure() method
Configure() {
LoadResources conffile paths
CheckResources conffile paths
# Update ld.so.conf file.
for i in $paths; do
line=`grep $i $conffile`
if [ -z "$line" ]; then
echo "$i" >> $conffile
fi
done
/sbin/ldconfig;
return $?;
}
German Cancio – WP4-install LCFG HOW-TO - n° 28
LCFGng and => release 2
German Cancio – WP4-install LCFG HOW-TO - n° 29
LCFGng (release 1.4)
Changes:
u LoadResources/CheckResources
beginning)
disappear (all resources loaded from the
u Resources
are accessed as LCFG_<component>_myresource (eg.
$LCFG_mycomponent_myresource)
u The
default start() method already calls Configure()
u Improved
uA
log rotating
template substitution processor allows for fast generation of config files
u Changes
n
documented under http://www.lcfg.org/doc/lcfg-ngeneric.pdf.
Example components available from EDG CVS.
uA
backwards compatibility module allows to import old-style components
without any modifications.
u The
EDG recommendations outlined in this talk still apply.
German Cancio – WP4-install LCFG HOW-TO - n° 30
LCFGng (II)
Perl component support
u Components
n
n
can be written also in Perl (same functionality available).
We recommend to phase out shell components.
See examples later on.
(EDG only) New component configuration access library
u This
library allows true hierarchical configuration structure access on the
client side
u Implements
n
a subset of the Node View Access API
http://cern.ch/hep-proj-grid-fabric/config/documents/nva
u Implemented
only for Perl components.
u The
server side (configuration and .def files) will continue to use key-value
pairs until after release 2.
German Cancio – WP4-install LCFG HOW-TO - n° 31
Perl components in LCFGng for EDG
#!/usr/bin/perl -w
package LCFG::MyComp;
@ISA = qw(LCFG::Component);
use strict;
use LCFG::Component;
use LCFG::Config; # EDG specific
sub Configure($$@) {
my ($self,$res) = @_;
my $config=LCFG::Config->new($res);
my $age=$config->getValue('/persons/John/age');
$self->Fail( "too young") unless ($age>18);
}
new LCFG::MyComp() -> Dispatch();
The component methods are the same,
but configuration access is simplified
German Cancio – WP4-install LCFG HOW-TO - n° 32
Perl components (II)
$self->Info ("disks configured: ");
my $disks=$config->getElement('/disks');
while ($disks->isNextElement()) {
my $disk_name=$disks->getNextElement();
$self->Info (“found disk: ".$disk_name);
my $partitions=$config->getElement ('/disks/'.$disk_name.'/partitions');
while ($partitions->isNextElement()) {
my $part_name=$partitions->getNextElement();
$self->Info (“found partition: ".$part_name);
}
}
With the NVA API, components can browse complex configurations,
structured as trees
German Cancio – WP4-install LCFG HOW-TO - n° 33
Documentation and links
u LCFGng
‘out of the box’: http://www.lcfg.org
u EDG
components and extensions: Check on the EDG CVS repository,
http://datagrid.in2p3.fr -> fabric_mgt/edg-lcfg
u New
n
EDG configuration access API:
http://cern.ch/hep-proj-grid-fabric/config/documents/nva
u Documentation
n
(HOW-TO):
http://datagrid.in2p3.fr/cgi-bin/cvsweb.cgi/fabric_mgt/edglcfg/COMPONENTS-HOWTO
u WP4-install
homepage: http://cern.ch/wp4-install
German Cancio – WP4-install LCFG HOW-TO - n° 34