2004.05_Managing System Configurations with System Configuration Profile Management.pdf

COVER STORY

SCPM

Environment Changing

Changing the operating environment

on a single machine, involves a lot of

configuration work. SCPM makes life

easier for Suse users by maintaining

profiles with different settings.

BY FALKO ZURELL

world of laptops. Portable machines

are especially prone to environment

changes. Although you typically hitch up

your laptop to the wired network to con-

nect to the outside world, you might use

a WLAN from time to time, or not have a

network connection at all. Although you

have a docking station with an external

screen at the office, at home you might

revert to the built-in display. Suse Linux

has SCPM, the System Configuration

Profile Management tool, to help your

machine adapt to its surrounds.

ent environment with a single com-

mand. As an alternative, you can simply

select a profile on booting.

SCPM has been a default Suse compo-

nent since version 8. Assuming you have

not manually deleted SCPM, the profile

manager should already be installed on

your Suse system.

The GUI-based YaST Profile manager

module, which is located in the System

group, helps you set up SCPM (see Fig-

ure 1), but you can also enter yast2

profile-manager to launch the tool

directly.

Existing profiles are displayed in the

profile manager’s main window. You can

add a new profile or modify the configu-

ration. The Options button allows you to

change or create resource groups (see

Figure 2).

Your current configuration is used as a

template when you create a new profile.

SCPM creates a directory with the new

profile name below /var/lib/scpm/pro-

files/ , and copies the configuration files

for the specified resource groups to that

directory.

Groups

Admins can use resource groups to spec-

ify the services to which the profile

settings apply. SCPM only saves your

printer settings if you enable the printer

group, for example. If you do not check

this resource, the printer is not affected

by a profile change, but simply keeps its

current settings.

A few pre-defined resource groups are

created when you install SCPM. These

groups cover most configurations and

include basic network settings ( net-

work ), the NTP service for time

synchronization across the Internet

( ntpd ), the firewall ( SuSEfirewall2 ), the

autofs automounter, which automati-

cally mounts disks. If this selection is not

to your liking, you can define your own

groups.

Unfortunately, the status display in the

main window of the YaST module is not

Sharp Profiles

SCPM saves complete collections of sys-

tem settings for various environments in

so-called profiles, allowing you to restore

them when needed. Profiles not only

store configuration files, but also addi-

tional information – such as whether

specific services have been enabled, or

not. That makes it possible to perform all

the changes required to adapt to a differ-

Table 1: SCPM Commands

Listing 1: Accessing SCPM’s database mode

and creating a new resource

Enable SCPM scpm enable

Create a new profile scpm add profile_name

Switch to another profile scpm switch profile_name

Save the changes to the active profile scpm save

Copy a profile scpm copy source_profile target_profile

Display the active profile scpm active

Display available profiles scpm list

Reload the settings of the current profile scpm reload

01 # scpm db

02 SCDB Utility (SCPM version 0.9.4)

03 > load

04 > create resource /opt/tomcat/conf/server.xml file

05 > save

06 > quit

May 2004

www.linux-magazine.com

Managing system configurations with SCPM

L inux is making inroads into the

SCPM

COVER STORY

Figure 1: YaST2 helps you configure SCPM.

Figure 2: SCPM Yast2 module – resource configuration.

reliable. It insists that the profile man-

ager is disabled, irrespective of its actual

status. Doubly enabling a profile should

not cause any harm, as SCPM does not

overwrite existing databases or profiles.

Or at least it requires you to explicitly

stipulate an overwrite in the command

line.

There are more or less no limits to

expanding the profile manager’s capabil-

ities, as you can tell SCPM to launch

pre-start and post-start or pre-stop and

post-stop scripts when loading or unload-

ing a profile (see Figure 3).

When you select a different profile,

SCPM first runs the two stop scripts, and

alerts you in case of unsaved changes. It

then goes on to launch the pre-start

script, retrieves the configuration files

for the new profile from the database,

and applies them to the system. SCPM

checks if services are running or not, and

ensures that the required status is

applied. The last step of the change

process is to call the post-stop script.

If you want to specify a profile when

booting a machine, you can stipulate

the PROFILE=profile_name parameter in

the boot menu to tell Suse to fire up

with the required settings. The

/etc/init.d/boot.scpm script ensures that

this works.

If you regularly change your profile on

booting, you might like to add a few

entries with pre-configured kernel

parameters to your bootloader confi-

guration (YaST2: System / Bootloader

Configuration ). To do so, add a new

section with the settings for the default

kernel and simply change the PROFILE

parameter to load the required profile the

next time you boot.

mode. (see Listing 1). The load com-

mand is extremely important here, as it

loads the current database for editing. If

you fail to load the current database, and

then save your settings, the current data-

base will be overwritten with a file that

contains only these changes.

Even if you overwrite the database by

mistake, there is no need to panic: SCPM

saves the last three versions of the

database in the /var/lib/scpm/scdb/

directory. The current database is called

scdb.db , the backup copies have a

few random characters added to their

names.

It is easy to create your own backup of

a profile you have created. You will need

more than just the database file, scdb.db .

To store the configuration files at the

same time, you will also need to copy the

/var/lib/scpm/profiles/ directory to a safe

location.

Command Line Set Up

Although YaST2 makes light work of

configuring SCPM, continually launch-

ing YaST to change a profile may start to

get on your nerves. The command line

provides an alternative. Make sure you

have root privileges – after all, you will

be modifying the system configuration –

and use a few simple commands to

speed up this task. Table 1 provides an

overview of the most important com-

mands. For example, scpm switch ISDN

enables a profile called ISDN .

Changes can only be applied to the

current profile, no matter whether you

use YaST2 or the command line to effect

them. To do so, first change your settings

in the usual way. When you have every-

thing working to your liking, simply call

scpm save to save

the changes. SCPM

will then display

the changes one by

one, and prompt

you to confirm that

they were deliber-

ate before saving

them to the profile.

If you need to

change configura-

tion files that SCPM

is ignoring due to

your resource set-

tings, you can

perform manual

changes in inter-

active database

■

Figure 3: Unlimited configuration options for profiles.

www.linux-magazine.com

May 2004

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