Operating Systems / Linux
Security
A closer look at Security.
Users, groups and permissions in Linux
Every process runs as a user with group memberships and file mode bits. This overview covers UIDs and GIDs, passwd and shadow, rwx and umask, special bits, ACLs, sudo, and PAM on Debian.
Linux security primitives
Beyond file modes, Linux isolates and constrains processes with capabilities, namespaces, cgroups, seccomp, and mandatory access control. This overview explains AppArmor on Debian, SELinux elsewhere, and how containers combine these kernel features.