kclient

- set up a machine as a Kerberos client

Synopsis

/usr/sbin/kclient [-n] [-R realm] [-k kdc] [-a adminuser] 
     [-c filepath] [-d dnsarg] [-f fqdn_list] [-p profile]

Description

You can use the kclient utility to:

• Configure a machine as a Kerberos client for a specified realm and for KDC by setting up krb5.conf(4).

• Add the Kerberos host principal to the local host's keytab file (/etc/krb5/krb5.keytab).

• Optionally set up the machine to do kerberized NFS.

• Optionally bring over a master krb5.conf copy from a specified pathname.

• Optionally setup a machine to do server and/or host/domain name-to-realm mapping lookups by means of DNS.

The kclient utility needs to be run on the client machine with root permission and can be run either interactively or non-interactively. In the non-interactive mode, the user feeds in the required inputs by means of a profile, command-line options, or a combination of profile and command-line options. The user is prompted for “required” parameter values (realm, kdc, and adminuser), if found missing in the non-interactive run. The interactive mode is invoked when the utility is run without any command-line arguments.

Both the interactive and non-interactive forms of kclient always add the host/fqdn entry to the local host's keytab file. They also require the user to enter the password for the administrative user requested, to obtain the Kerberos Ticket Granting Ticket (TGT) for adminuser. The host/fqdn, nfs/fqdn, and root/fqdn principals are added to the KDC database (if not already present) before their addition to the local host's keytab.

The kclient utility assumes that the local host has been setup for DNS and requires the presence of a valid resolv.conf(4). Also, kclient can fail if the localhost time is not synchronized with that of the KDC. For Kerberos to function the localhost time must be within five minutes of that of the KDC. It is advised that both systems run some form of time synchronization protocol, such as the Network Time Protocol (NTP). See xntpd(1M).

Options

The non-interactive mode supports the following options:

-n

Set up the machine for kerberized NFS. This involves making changes to nfssec.conf(4) and addition of the nfs/fqdn and root/fqdn entries to the local host's keytab file.

-R [ realm ]

Specifies the Kerberos realm.

-k [ kdc ]

Specifies the machine to be used as the Kerberos Key Distribution Center (KDC).

-a [ adminuser ]

Specifies the Kerberos administrative user.

-c [ filepath ]

Specifies the pathname to the krb5.conf(4) master file, to be copied over to the local host. The path specified normally points to a master copy on a remote host and brought over to the local host by means of NFS.

-d [ dnsarg ]

Specifies the DNS lookup option to be used and specified in the krb5.conf(4) file. Valid dnsarg entries are: none, dns_lookup_kdc, dns_lookup_realm and dns_fallback. Any other entry is considered invalid. The latter three dnsarg values assume the same meaning as those described in krb5.conf. dns_lookup_kdc implies DNS lookups for the KDC and the other servers. dns_lookup_realm is for host/domain name-to-realm mapping by means of DNS. dns_fallback is a superset and does DNS lookups for both the servers and the host/domain name-to-realm mapping. A lookup option of none specifies that DNS is not be used for any kind of mapping lookup.

-f [ fqdn_list ]

This option creates a service principal entry (host/nfs/root) associated with each of the listed fqdn's, if required, and subsequently adds the entries to the local host's keytab.

fqdn_list is a comma-separated list of one or more fully qualified DNS domain names.

This option is especially useful in Kerberos realms having systems offering kerberized services, but situated in multiple different DNS domains.

-p [ profile ]

Specifies the profile to be used to enable the reading in of the values of all the parameters required for setup of the machine as a Kerberos client.

The profile should have entries in the format:

PARAM <value>

Valid PARAM entries are: REALM, KDC, ADMIN, FILEPATH, NFS, DNSLOOKUP, and FQDN. These profile entries correspond to the -R [realm], -k [kdc], -a [adminuser], -c [filepath], -n, -d [dnsarg], and -f [fqdn_list] command-line options, respectively. Any other PARAM entry is considered invalid and is ignored.

The NFS profile entry can have a value of 0 (do nothing) or 1 (operation is requested). Any other value is considered invalid and is ignored.

Keep in mind that the command line options override the PARAM values listed in the profile.

Examples

Example 1 Setting Up a Kerberos Client Using Command-Line Options

To setup a Kerberos client using the clntconfig/admin administrative principal for realm 'ABC.COM', kdc `example1.com' and that also does kerberized NFS, enter:

# /usr/sbin/kclient -n -R ABC.COM -k example1.com -a clntconfig

Alternatively, to set up a Kerberos client using the clntconfig/admin administrative principal for the realm `EAST.ABC.COM', kdc `example2.east.abc.com' and that also needs service principal(s) created and/or added to the local keytab for multiple DNS domains, enter:

# /usr/sbin/kclient -n -R EAST.ABC.COM -k example2.east.abc.com \
-f west.abc.com,central.abc.com -a clntconfig

Note that the krb5 administrative principal used by the administrator needs to have only add, inquire, change-pwd and modify privileges (for the principals in the KDC database) in order for the kclient utility to run. A sample kadm5.acl(4) entry is:

clntconfig/admin@ABC.COM acmi

Example 2 Setting Up a Kerberos Client Using the Profile Option

To setup a Kerberos client using the clntconfig/admin administrative principal for realm `ABC.COM', kdc `example1.com' and that also copies over the master krb5.conf from a specified location, enter:

# /usr/sbin/kclient -p /net/example1.com/export/profile.krb5

The contents of profile.krb5:

REALM ABC.COM
KDC example1
ADMIN clntconfig
FILEPATH /net/example1.com/export/krb5.conf
NFS 0
DNSLOOKUP none

Files

/etc/krb5/kadm5.acl

Kerberos access control list (ACL) file.

/etc/krb5/krb5.conf

Default location for the local host's configuration file.

/etc/krb5/krb5.keytab

Default location for the local host's keytab file.

/etc/nfssec.conf

File listing NFS security modes.

/etc/resolv.conf

DNS resolver configuration file.

Attributes

See attributes(5) for descriptions of the following attributes:

See Also

xntpd(1M), kadm5.acl(4), krb5.conf(4), nfssec.conf(4), resolv.conf(4), attributes(5)

Notes

fqdn stands for the Fully Qualified Domain Name of the local host. The kclient utility saves copies of both the krb5.conf(4) and nfssec.conf(4) files to files with corresponding names and .sav extensions. The optional copy of the krb5.conf(4) master file is neither encrypted nor integrity-protected and it takes place over regular NFS.