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Linux From Scratch - Version 7.0

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6.55.2. Configuring Shadow

This package contains utilities to add, modify, and delete users and groups; set and change their passwords; and

perform other administrative tasks. For a full explanation of what password shadowing means, see the doc/HOWTO

file within the unpacked source tree. If using Shadow support, keep in mind that programs which need to verify

passwords (display managers, FTP programs, pop3 daemons, etc.) must be Shadow-compliant. That is, they need to

be able to work with shadowed passwords.

To enable shadowed passwords, run the following command:

pwconv

To enable shadowed group passwords, run:

grpconv

Shadow's stock configuration for the useradd utility has a few caveats that need some explanation. First, the default

action for the useradd utility is to create the user and a group of the same name as the user. By default the user ID

(UID) and group ID (GID) numbers will begin with 1000. This means if you don't pass parameters to useradd, each

user will be a member of a unique group on the system. If this behaviour is undesireable, you'll need to pass the -

g parameter to useradd. The default parameters are stored in the /etc/default/useradd file. You may need

to modify two parameters in this file to suit your particular needs.

/etc/default/useradd Parameter Explanations

GROUP=1000

This parameter sets the beginning of the group numbers used in the /etc/group file. You can modify it to anything

you desire. Note that useradd will never reuse a UID or GID. If the number identified in this parameter is used,

it will use the next available number after this. Note also that if you don't have a group 1000 on your system the

first time you use useradd without the -g parameter, you'll get a message displayed on the terminal that says:

useradd: unknown GID 1000. You may disregard this message and group number 1000 will be used.

CREATE_MAIL_SPOOL=yes

This parameter causes useradd to create a mailbox file for the newly created user. useradd will make the group

ownership of this file to the mail group with 0660 permissions. If you would prefer that these mailbox files

are not created by useradd, issue the following command:

sed -i 's/yes/no/' /etc/default/useradd

6.55.3. Setting the root password

Choose a password for user root and set it by running:

passwd root

6.55.4. Contents of Shadow

Installed programs: chage, chfn, chgpasswd, chpasswd, chsh, expiry, faillog, gpasswd, groupadd, groupdel,

groupmems, groupmod, grpck, grpconv, grpunconv, lastlog, login, logoutd, newgrp,

newusers, nologin, passwd, pwck, pwconv, pwunconv, sg (link to newgrp), su, useradd,

userdel, usermod, vigr (link to vipw), and vipw

Installed directory: /etc/default

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MTD 248-645A Manual de usuario Pagina 200