Topic

Linux security

Linux security guides from Tryssh: practical diagnostics, safe operating procedures, and production runbooks for server operators.

Move an AppArmor profile from complain to enforce with evidence

AppArmor applies path-based rules from a loaded profile; complain logs would-be denials while enforce blocks them.

The Tryssh team · July 29, 2026

Add a Linux audit rule that produces useful evidence without flooding

Audit rules select kernel events by syscall, path, fields, and key; ordering and never rules can suppress later matches.

The Tryssh team · July 29, 2026

Replace setuid root with the narrow Linux capability actually required

Capabilities divide traditional root privilege into independently checked units that can be attached to a file or bounded in a service process.

The Tryssh team · July 29, 2026

Set a service umask without assuming it repairs existing files

Umask removes permission bits during creation; it does not change existing objects and applications can request narrower modes afterward.

The Tryssh team · July 29, 2026

Back up and validate an nftables ruleset before firewall changes

Nft list ruleset emits the active rules in restorable syntax, but runtime-generated state and surrounding network dependencies still need separate evidence.

The Tryssh team · July 29, 2026

Configure pam_faillock without locking out every administrator

Pam_faillock records failed authentication events and PAM stack placement determines preauth, authfail, account enforcement, reset, and local-user behavior.

The Tryssh team · July 29, 2026

Repair SELinux file contexts persistently with semanage and restorecon

SELinux path labeling policy maps pathname patterns to expected contexts; restorecon applies that policy while chcon creates a local label that relabeling may erase.

The Tryssh team · July 29, 2026

Trace sudoers include order with visudo before changing privilege

Sudo reads its main policy and included files in lexical or directive order; the last matching tag and command rules can change effective authorization.

The Tryssh team · July 29, 2026

Apply Linux sysctl hardening with precedence and runtime verification

Sysctl settings come from kernel defaults and ordered configuration sources; loading one file can differ from the complete boot-time merge.

The Tryssh team · July 29, 2026

Use systemd-analyze security to guide service hardening

Systemd-analyze security inspects configured sandbox properties and reports an exposure score, but it cannot infer application requirements or every kernel boundary.

The Tryssh team · July 29, 2026