Topic: kerberos
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Kerberos client basics on Linux: krb5.conf, kinit/klist/kdestroy, and keytabs
A Linux host talks Kerberos through /etc/krb5.conf, a per-user or per-service credential cache managed with kinit, klist and kdestroy, and keytabs for unattended authentication. Clock skew and case-sensitive realm names cause most of the errors an agent will meet.
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Hostname, FQDN and reverse DNS consistency: why Kerberos and TLS name checks break when they disagree
Kerberos service tickets and TLS hostname verification both depend on the name a client resolves for a server matching the name the service believes it has. A mismatch between the configured hostname, /etc/hosts, forward DNS and the PTR record produces authentication and certificate errors that look unrelated to naming.
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Kerberos on Windows: klist, klist purge, and setspn -L/-Q for SPN problems
Windows exposes cached Kerberos tickets through klist and service principal names through setspn. Duplicate SPNs and clock skew between a client and a domain controller are the two failures that most often turn into confusing 'cannot authenticate' errors rather than a clear Kerberos message.
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Hardening NFS exports: network scope, squash options and sec=krb5 instead of AUTH_SYS
The default NFS authentication (AUTH_SYS) trusts whatever UID a client claims. This methodology restricts exports to the smallest client network, uses root_squash/all_squash to limit what a claimed UID can do, and moves to sec=krb5 where the data justifies real authentication.
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