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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)).

You can run any command 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:

umulus@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.

CategoryPrivilegeExample Commandsudoers Entry
MonitoringSwitch port informationethtool -m swp1%noc ALL=(ALL) NOPASSWD:/sbin/ethtool
MonitoringSystem diagnosticscl-support%noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/cl-support
MonitoringRouting diagnosticscl-resource-query%noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/cl-resource-query
Image managementInstall imagesonie-select http://lab/install.bin%noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/onie-select
Package managementAny apt-get commandapt-get update or apt-get install%noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get
Package managementJust apt-get updateapt-get update%noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get update
Package managementInstall packagesapt-get install vim%noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get install *
Package managementUpgradingapt-get upgrade%noc ALL=(ALL) NOPASSWD:/usr/bin/apt-get upgrade
NetfilterInstall ACL policiescl-acltool -i%noc ALL=(ALL) NOPASSWD:/usr/cumulus/bin/cl-acltool
NetfilterList iptables rulesiptables -L%noc ALL=(ALL) NOPASSWD:/sbin/iptables
L1 + 2 featuresAny LLDP commandlldpcli show neighbors / configure%noc ALL=(ALL) NOPASSWD:/usr/sbin/lldpcli
L1 + 2 featuresJust show neighborslldpcli show neighbors%noc ALL=(ALL) NOPASSWD:/usr/sbin/lldpcli show neighbors*
InterfacesModify any interfaceip link set dev swp1 {updown}
InterfacesUp any interfaceifup swp1%noc ALL=(ALL) NOPASSWD:/sbin/ifup
InterfacesDown any interfaceifdown swp1%noc ALL=(ALL) NOPASSWD:/sbin/ifdown
InterfacesUp/down only swp2ifup swp2 / ifdown swp2%noc ALL=(ALL) NOPASSWD:/sbin/ifup swp2,/sbin/ifdown swp2
InterfacesAny IP address changeip addr {adddel} 192.0.2.1/30 dev swp1
InterfacesOnly set IP addressip addr add 192.0.2.1/30 dev swp1%noc ALL=(ALL) NOPASSWD:/sbin/ip addr add *
Ethernet bridgingAny bridge commandbrctl addbr br0 / brctl delif br0 swp1%noc ALL=(ALL) NOPASSWD:/sbin/brctl
Ethernet bridgingAdd bridges and interfacesbrctl addbr br0 / brctl addif br0 swp1%noc ALL=(ALL) NOPASSWD:/sbin/brctl addbr *,/sbin/brctl addif *
Spanning treeSet STP propertiesmstpctl setmaxage br2 20%noc ALL=(ALL) NOPASSWD:/sbin/mstpctl
TroubleshootingRestart switchdsystemctl restart switchd.service%noc ALL=(ALL) NOPASSWD:/usr/sbin/service switchd *
TroubleshootingRestart any servicesystemctl cron switchd.service%noc ALL=(ALL) NOPASSWD:/usr/sbin/service
TroubleshootingPacket capturetcpdump%noc ALL=(ALL) NOPASSWD:/usr/sbin/tcpdump
L3Add static routesip route add 10.2.0.0/16 via 10.0.0.1%noc ALL=(ALL) NOPASSWD:/bin/ip route add *
L3Delete static routesip route del 10.2.0.0/16 via 10.0.0.1%noc ALL=(ALL) NOPASSWD:/bin/ip route del *
L3Any static route changeip route *%noc ALL=(ALL) NOPASSWD:/bin/ip route *
L3Any iproute commandip *%noc ALL=(ALL) NOPASSWD:/bin/ip
L3Non-modal OSPFcl-ospf area 0.0.0.1 range 10.0.0.0/24%noc ALL=(ALL) NOPASSWD:/usr/bin/cl-ospf