This documentation is for the extended support release (ESR) version of Cumulus Linux. We will continue to keep this content up to date until 21 February, 2023, when ESR support ends. For more information about ESR, please read this knowledge base article.

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Using sudo to Delegate Privileges

By default, Cumulus Linux has two user accounts: root and cumulus. The cumulus account is a normal user and is in the group sudo.

You can add more user accounts as needed. Like the cumulus account, these accounts must use sudo to execute privileged commands.

sudo Basics

sudo allows you to execute a command as superuser or another user as specified by the security policy. See man sudo(8) for details.

The default security policy is sudoers, which is configured using /etc/sudoers. Use /etc/sudoers.d/ to add to the default sudoers policy. See man sudoers(5) for details.

Use visudo only to edit the sudoers file; do not use another editor like vi or emacs. See man visudo(8) for details.

When creating a new file in /etc/sudoers.d, use visudo -f. This option performs sanity checks before writing the file to avoid errors that prevent sudo from working.

Errors in the sudoers file can result in losing the ability to elevate privileges to root. You can fix this issue only by power cycling the switch and booting into single user mode. Before modifying sudoers, enable the root user by setting a password for the root user.

By default, users in the sudo group can use sudo to execute privileged commands. To add users to the sudo group, use the useradd(8) or usermod(8) command. To see which users belong to the sudo group, see /etc/group (man group(5)).

Any command can be run as sudo, including su. A password is required.

The example below shows how to use sudo as a non-privileged user cumulus to bring up an interface:

cumulus@switch:~$ ip link show dev swp1
3: swp1: <BROADCAST,MULTICAST> mtu 1500 qdisc pfifo_fast master br0 state DOWN mode DEFAULT qlen 500
link/ether 44:38:39:00:27:9f brd ff:ff:ff:ff:ff:ff
 
cumulus@switch:~$ ip link set dev swp1 up
RTNETLINK answers: Operation not permitted
 
cumulus@switch:~$ sudo ip link set dev swp1 up
Password:
 
cumulus@switch:~$ ip link show dev swp1
3: swp1: <BROADCAST,MULTICAST,UP,LOWER_UP> mtu 1500 qdisc pfifo_fast master br0 state UP mode DEFAULT qlen 500
link/ether 44:38:39:00:27:9f brd ff:ff:ff:ff:ff:ff

sudoers Examples

The following examples show how you grant as few privileges as necessary to a user or group of users to allow them to perform the required task. For each example, the system group noc is used; groups are prefixed with an %.

When executed by an unprivileged user, the example commands below must be prefixed with sudo.

Debian wiki - sudo