# Linux Security Updates

## APT

List packages with available upgrades:

```bash
apt list --upgradable
```

APT does not reliably label which available upgrades are security updates.
On Ubuntu and Debian, use `unattended-upgrade` to identify applicable security
updates:

```bash
sudo unattended-upgrade --dry-run --debug
```

To preview all package upgrades without installing them:

```bash
apt upgrade --simulate
```

The listing and simulated-upgrade commands usually do not require `sudo`.
Refresh package metadata with `sudo apt update` when necessary.

## Yum and DNF

List available security-update advisories:

```bash
yum updateinfo list updates security
dnf updateinfo list updates security
```

These advisory-listing commands do not require `sudo`.

To preview the packages updated by a security-only transaction without making
changes:

```bash
sudo yum update --security --assumeno
sudo dnf upgrade --security --assumeno
```

`--assumeno` prevents the transaction from being applied. These commands may
still require `sudo` because Yum and DNF treat them as upgrade transactions.