Add nodev Option to /var
Mounts /var with the nodev option so the kernel refuses to interpret device files placed in that directory.
Checked against the resolved running state (e.g. sshd -T, sysctl, systemctl show), catches drop-ins and Includes a file read would miss. Caveat: runtime ≠ persistence; a value correct now may not survive a reboot.
Pavois asserts the effective configuration, the live, resolved state, not a file. File-based scanners (OVAL/SCAP, Lynis) miss Includes, drop-ins and runtime defaults; this check sees what is actually applied.
A mapping is a cross-reference to where each standard places this requirement, anchored and cross-validated, not a claim of equivalence. A passing check is evidence toward these references, how to read it.
Why this rule matters
The only legitimate place for device files is /dev on the root partition (chroot jails being the rare exception). /var holds variable data, logs, spool, caches, databases, and should never contain device nodes. Mounting it with nodev tells the kernel to ignore any character or block special device found there, preventing an attacker who can write under /var from planting a device node to bypass filesystem permissions and access raw disk or kernel memory.
What Pavois checks
Pavois inspects the effective mount with mount('/var') and asserts its resolved options include nodev. It reads the live kernel mount table, what is actually enforced, rather than /etc/fstab, so it catches a partition remounted without the flag, a systemd mount-unit override, or an fstab entry that never applied, which a file-based scanner would wrongly pass.
describe mount('/var') do
its('options') { should include 'nodev' }
end
describe command("{ findmnt --fstab -no OPTIONS /var 2>/dev/null; grep -hsE '[[:space:]]/var[[:space:]]' /etc/fstab 2>/dev/null; systemctl show -p Options -- $(systemd-escape -p --suffix=mount /var 2>/dev/null) 2>/dev/null; } | grep -ow 'nodev'") do
its('stdout') { should match(/\S/) }
endHow to verify it is applied
Run findmnt /var (or findmnt -no OPTIONS /var) and confirm nodev is in the option list. Expected output contains nodev, e.g. /var ... rw,nosuid,nodev,relatime.
Inspect & investigate
Mount state is queried live with findmnt /var or cat /proc/mounts, not from a log. Boot-time and remount events appear via journalctl -b | grep -i /var.
Remediation
No automated harden plan ships for this rule yet, so it must be applied manually: this requires /var to be a separate partition. Add nodev to its /etc/fstab entry, then mount -o remount /var, or reboot, and re-scan to confirm.
Pavois applies this with its own harden engine, the plan below, not a shell script:
| command | awk -v m=/var -v o=nodev '$0!~/^[[:space:]]*#/&&$2==m{n=split($4,a,",");h=0;for(i=1;i<=n;i++)if(a[i]==o)h=1;if(!h)$4=$4","o}{print}' /etc/fstab >/etc/.fstab.pav && cat /etc/.fstab.pav >/etc/fstab && rm -f /etc/.fstab.pav; mountpoint -q /var && mount -o remount,nodev /var || true |
|---|---|
| name | mount-var-nodev |
| not_if | awk -v m=/var '$2==m&&$0!~/^[[:space:]]*#/{print $4}' /etc/fstab | tr , '\n' | grep -qx nodev |
| resource | exec |
pavois harden plan localwhere the target is local, a user@host SSH alias, or a container , Docs
Impact & precautions
Functional impact is essentially nil, /var never needs device nodes (note: nodev does not affect noexec/nosuid, so keep /var executable since many services run from /var/lib). Precautions: the option can only be set if /var is a dedicated partition; on a default layout you must first carve it out, which is among the most disruptive partition changes (it holds running databases, package caches, container storage and logs) and requires planning, data migration with services stopped, and a reboot. Remounting a busy /var live often fails, prefer applying at the next reboot.
Standards mapping
| Standard | Reference | Type | Version | Confidence |
|---|---|---|---|---|
| CIS | 1.1.2.4.2 | direct | per OS, see the benchmark table | high |
| NIST | AC-6, AC-6(1), CM-6(a), CM-7(a), CM-7(b), MP-7 | supporting | 800-53 Rev 5 · 800-171 Rev 2 (pinned) | medium |
Each reference is a cross-reference anchored in the upstream benchmark and cross-validated against the SCAP Security Guide and ansible-lockdown, not a claim of equivalence. Direct = a prescriptive, line-level requirement; supporting = an abstract control family (NIST) the check provides evidence toward. How to read a mapping.