U2 Secured vs Duo for SSH and Linux sign-in
Both put a push approval in front of SSH and sudo. U2 Secured adds number matching on every plan, codes that work when the machine is offline, and the Ubuntu login and lock screens, and it is priced per developer account, not per user.
What follows is the Linux comparison, read from Duo’s own pricing and Duo Unix documentation and dated.
Where U2 Secured is different
Number matching on every plan
Every push asks the user to pick the number shown at the login, free plan included. A wrong pick denies the sign-in.
Signs in when the machine is offline
Codes from the authenticator app and single-use backup codes are checked on the machine itself, so a server cut off from the internet, or a laptop before its Wi-Fi connects, still lets the right person in.
Refuses rather than opens by default
When U2 Secured cannot be reached and the user has no code, the login is refused unless you choose otherwise. Letting the password alone through is a setting you turn on, not the default.
The Ubuntu desktop too
The same package covers the login screen, the lock screen, sudo, su and admin prompts on Ubuntu, and they continue by themselves once the phone approves.
Linux sign-in, side by side
Every Duo entry is read from Duo’s own site; the link on each row goes to it, dated the day it was read.
Installing U2 Secured on a machine
- 1
From the signed U2 Secured repository
Check the key fingerprint before trusting it; apt upgrade then brings each release. The setup guide covers the app, registering machines and enrolling users.
curl -fsSL https://u2secured.com/downloads/linux/u2secured.gpg | sudo tee /usr/share/keyrings/u2secured.gpg > /dev/null gpg --show-keys /usr/share/keyrings/u2secured.gpg # B725 4213 9302 02C4 8B19 6810 E6C4 2653 4D95 43BA echo "deb [signed-by=/usr/share/keyrings/u2secured.gpg] https://u2secured.com/downloads/linux stable main" \ | sudo tee /etc/apt/sources.list.d/u2secured.list sudo apt update && sudo apt install u2auth u2auth-admin help
What U2 Secured costs
Flat monthly plans per developer account. At Duo Essentials’ list price of $3 per user per month, the $99 Growth plan costs the same as 33 users, and covers up to 25,000. Against Duo Premier at $9, it is the price of 11.
| Plan | Price | Includes |
|---|---|---|
| Developer | Free | 1,000 active users and 100 push approvals a month, 1 app. Codes are unlimited. |
| Growth | $99/month | 25,000 active users and 100,000 push approvals a month, 5 apps. Codes are unlimited. |
| Team | $149/month | 75,000 active users and 300,000 push approvals a month, 20 apps. Codes are unlimited. |
| Scale | $199/month | 250,000 active users and 1,000,000 push approvals a month, unlimited apps. Codes are unlimited. |
One flat monthly price per developer account, not a price per user or per machine. A fleet of servers is one app; each person who signs in counts once a month however many machines they use. Codes from the app (TOTP) and backup codes are never metered on any plan.
Questions people ask when comparing
- Is U2 Secured cheaper than Duo?
- The Growth plan is $99 a month flat for up to 25,000 active users. At Duo’s list prices that is the cost of 33 users on Essentials or 11 on Premier, and every user beyond those is included.
- Can I keep using SSH keys?
- Yes. sshd can require the key and then the U2 Secured approval, so a stolen key alone is not enough.
- What happens to logins if U2 Secured is unreachable?
- The login asks for a code from the authenticator app or a backup code, checked on the machine. With neither, it refuses by default; you can choose to let the password alone through instead.
- Do my users need a new app?
- Yes: the U2 Secured Authenticator, free on the App Store and Google Play. It also holds ordinary two-factor codes for other sites.
Sources for the Duo side
Every Duo figure above was read from duo.com on the date shown. Duo changes its plans from time to time; its own pages are the authority if anything here has changed.
- Duo — Pricing · read 2026-10-24
- Duo — Duo Unix documentation · read 2026-10-24
- Duo — Windows Logon (offline access) · read 2026-10-24
- Duo — macOS (offline access) · read 2026-10-24