Various add-on packages enable RADIUS users to log in to Cumulus Linux switches in a transparent way with minimal configuration. There is no need to create accounts or directories on the switch. Authentication is handled with PAM and includes login,
Install the RADIUS Packages
You can install the RADIUS packages even if the switch is not connected to the internet, as they are contained in the
cumulus-local-apt-archive repository that is embedded in the Cumulus Linux image.
To install the RADIUS packages:
cumulus@switch:~$ sudo apt-get update cumulus@switch:~$ sudo apt-get install libnss-mapuser libpam-radius-auth
After installation is complete, either reboot the switch or run the
sudo systemctl restart netd command.
libpam-radius-auth package supplied with the Cumulus Linux RADIUS client is a newer version than the one in Debian Buster. This package contains support for IPv6, the
src_ip option described below, as well as a number of bug fixes and minor features. The package also includes VRF support, provides man pages describing the PAM and RADIUS configuration, and sets the
SUDO_PROMPT environment variable to the login name for RADIUS mapping support.
libnss-mapuser package is specific to Cumulus Linux and supports the
getgrgid library interfaces. These interfaces add logged in RADIUS users to the group member list for groups that contain the
radius_user) if the RADIUS account is unprivileged, and add privileged RADIUS users to the group member list for groups that contain the
radius_priv_user) during the group lookups.
During package installation:
- The PAM configuration is modified automatically using
pam-auth-update (8), and the NSS configuration file
/etc/nsswitch.confis modified to add the mapuser and mapuid plugins. If you remove or purge the packages, these files are modified to remove the configuration for these plugins.
radius_shellpackage is added, which installs the
setcap cap_setuidprogram used as the login shell for RADIUS accounts. The package adjusts the
UIDwhen needed, then runs the bash shell with the same arguments. When installed, the package changes the shell of the RADIUS accounts to
/sbin//radius_shell, and to
/bin/shellif the package is removed. This package is required for privileged RADIUS users to be enabled. It is not required for regular RADIUS client use.
radius_useraccount is added to the
netshowgroup and the
radius_priv_useraccount to the
sudogroups. This change enables all RADUS logins to run NCLU
net showcommands and all privileged RADIUS users to also run
net del, and
net commitcommands, and to use
Configure the RADIUS Client
To configure the RADIUS client, edit the
Add the hostname or IP address of at least one RADIUS server (such as a freeradius server on Linux), and the shared secret used to authenticate and encrypt communication with each server.
The hostname of the switch must be resolvable to an IP address, which, in general, is fixed in DNS. If for some reason you cannot find the hostname in DNS, you can add the hostname to the
/etc/hostsfile manually. However, this can cause problems since the IP address is usually assigned by DHCP, which can change at any time.
Multiple server configuration lines are verified in the order listed. Other than memory, there is no limit to the number of RADIUS servers you can use.
The server port number or name is optional. The system looks up the port in the
/etc/servicesfile. However, you can override the ports in the
If the server is slow or latencies are high, change the
timeoutsetting. The setting defaults to 3 seconds.
If you want to use a specific interface to reach the RADIUS server, specify the
src_ipoption. You can specify the hostname of the interface, an IPv4, or an IPv6 address. If you specify the
src_ipoption, you must also specify the
vrf-namefield. This is typically set to mgmt if you are using a management VRF. You cannot specify more than one VRF.
The configuration file includes the
mapped_priv_user field that sets the account used for privileged RADIUS users and the
priv-lvl field that sets the minimum value for the privilege level to be considered a privileged login (the default value is 15). If you edit these fields, make sure the values match those set in the
The following example provides a sample
/etc/pam_radius_auth.conf file configuration:
mapped_priv_user radius_priv_user # server[:port] shared_secret timeout (secs) src_ip 192.168.0.254 secretkey other-server othersecret 3 192.168.1.10 # when mgmt vrf is in use vrf-name mgmt
If this is the first time you are configuring the RADIUS client, uncomment the
debug line to help with troubleshooting. The debugging messages are written to
/var/log/syslog. When the RADIUS client is working correctly, comment out the
As an optional step, you can set PAM configuration keywords by editing the
/usr/share/pam-configs/radius file. After you edit the file, you must run the
pam-auth-update --package command. PAM configuration keywords are described in the
pam_radius_auth (8) man page.
The privilege level for the user on the switch is determined by the value of the VSA (Vendor Specific Attribute)
shell:priv-lvl. If the attribute is not returned, the user is unprivileged. The following shows an example using the freeradius server for a fully-privileged user.
Service-Type = Administrative-User, Cisco-AVPair = "shell:roles=network-administrator", Cisco-AVPair += "shell:priv-lvl=15"
The VSA vendor name (Cisco-AVPair in the example above) can have any content. The RADIUS client only checks for the string
Enable Login without Local Accounts
Because LDAP is not commonly used with switches and adding accounts locally is cumbersome, Cumulus Linux includes a mapping capability with the
Mapping is done using two NSS (Name Service Switch) plugins, one for account name, and one for UID lookup. These accounts are configured automatically in
/etc/nsswitch.conf during installation and are removed when the package is removed. See the
nss_mapuser (8) man page for the full description of this plugin.
A username is mapped at login to a fixed account specified in the configuration file, with the fields of the fixed account used as a template for the user that is logging in.
For example, if the name being looked up is dave and the fixed account in the configuration file is radius_user, and that entry in
then the matching line returned by running
getent passwd dave is:
cumulus@switch:~$ getent passwd dave dave:x:1017:1002:dave mapped user:/home/dave:/bin/bash
The home directory
/home/dave is created during the login process if it does not already exist and is populated with the standard skeleton files by the
The configuration file
/etc/nss_mapuser.conf is used to configure the plugins. The file includes the mapped account name, which is
radius_user by default. You can change the mapped account name by editing the file. The
nss_mapuser (5) man page describes the configuration file.
A flat file mapping is done based on the session number assigned during login, which persists across
sudo. The mapping is removed at logout.
Local Fallback Authentication
If a site wants to allow local fallback authentication for a user when none of the RADIUS servers can be reached you can add a privileged user account as a local account on the switch. The local account must have the same unique identifier as the privileged user and the shell must be the same.
To configure local fallback authentication:
- Add a local privileged user account. For example, if the
radius_priv_useraccount in the
radius_priv_user:x:1002:1001::/home/radius_priv_user:/sbin/radius_shell, run the following command to add a local privileged user account named johnadmin:
``` cumulus@switch:~$ sudo useradd -u 1002 -g 1001 -o -s /sbin/radius_shell johnadmin ```
To enable the local privileged user to run
sudoand NCLU commands, run the following commands:
cumulus@switch:~$ sudo adduser johnadmin netedit cumulus@switch:~$ sudo adduser johnadmin sudo cumulus@switch:~$ sudo systemctl restart netd
/etc/passwdfile to move the local user line before to the
``` cumulus@switch:~$ sudo vi /etc/passwd ... johnadmin:x:1002:1001::/home/johnadmin:/sbin/radius_shell radius_priv_user:x:1002:1001::/home/radius_priv_user:/sbin/radius_shell ```
To set the local password for the local user, run the following command:
cumulus@switch:~$ sudo passwd johnadmin
Verify RADIUS Client Configuration
To verify that the RADIUS client is configured correctly, log in as a non-privileged user and run a
net add interface command.
In this example, the
ops user is not a privileged RADIUS user so they cannot add an interface.
ops@leaf01:~$ net add interface swp1 ERROR: User ops does not have permission to make networking changes.
In this example, the
admin user is a privileged RADIUS user (with privilege level 15) so is able to add interface swp1.
admin@leaf01:~$ net add interface swp1 admin@leaf01:~$ net pending --- /etc/network/interfaces 2018-04-06 14:49:33.099331830 +0000 +++ /var/run/nclu/iface/interfaces.tmp 2018-04-06 16:01:16.057639999 +0000 @@ -3,10 +3,13 @@ source /etc/network/interfaces.d/*.intf # The loopback network interface auto lo iface lo inet loopback # The primary network interface auto eth0 iface eth0 inet dhcp + +auto swp1 iface swp1 ...
Remove RADIUS Client Packages
Remove the RADIUS packages with the following command:
cumulus@switch:~$ sudo apt-get remove libnss-mapuser libpam-radius-auth
When you remove the packages, the plugins are removed from the
/etc/nsswitch.conf file and from the PAM files.
To remove all configuration files for these packages, run:
cumulus@switch:~$ sudo apt-get purge libnss-mapuser libpam-radius-auth
The RADIUS fixed account is not removed from the
/etc/group file and the home directories are not removed. They remain in case there are modifications to the account or files in the home directories.
To remove the home directories of the RADIUS users, first get the list by running:
cumulus@switch:~$ sudo ls -l /home | grep radius
For all users listed, except the radius_user, run this command to remove the home directories:
cumulus@switch:~$ sudo deluser --remove-home USERNAME
where USERNAME is the account name (the home directory relative portion). This command gives the following warning because the user is not listed in the
userdel: cannot remove entry 'USERNAME' from /etc/passwd /usr/sbin/deluser: `/usr/sbin/userdel USERNAME' returned error code 1. Exiting.
After removing all the RADIUS users, run the command to remove the fixed account. If the account has been changed in the
/etc/nss_mapuser.conf file, use that account name instead of radius_user.
cumulus@switch:~$ sudo deluser --remove-home radius_user cumulus@switch:~$ sudo deluser --remove-home radius_priv_user cumulus@switch:~$ sudo delgroup radius_users
- If two or more RADIUS users are logged in simultaneously, a UID lookup only returns the user that logged in first. Any processes run by either user get attributed to both, and all files created by either user get attributed to the first name matched. This is similar to adding two local users to the password file with the same UID and GID, and is an inherent limitation of using the UID for the fixed user from the password file. The current algorithm returns the first name matching the UID from the mapping file; this might be the first or second user that logged in.
- When you have both the TACACS+ and the RADIUS AAA client installed, RADIUS login is not attempted. As a workaround, do not install both the TACACS+ and the RADIUS AAA client on the same switch.