You added the line `helpdesk: alice, bob` to /etc/aliases, but mail to helpdesk still bounces. What is the most likely reason?
LPIC-1 Exam 102-500, objective 108. Essential system services medium
Draft — not checked yet. This question was written from the published exam objectives and cites the clause it comes from, but nobody has yet read it against that clause and signed for it.
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The options
Correct The alias file has not been rebuilt into the indexed database the MTA actually reads.
Correct. The MTA consults a compiled database (typically /etc/aliases.db), not the text file. Running `newaliases` regenerates it, after which the alias resolves.
Not correct Aliases only work for local users, and alice and bob must be listed by UID rather than by name.
Wrong. Alias targets are written as user names or full email addresses. UIDs are never used in /etc/aliases.
Not correct An alias may expand to only one recipient, so a comma-separated list is rejected.
Wrong. A comma-separated list of recipients is the normal way to write a distribution alias.
Not correct /etc/aliases is read only at boot, so the machine must be rebooted.
Wrong. No reboot is involved. The file is turned into the database on demand by newaliases, and the running MTA picks the new database up without restarting.
Why
/etc/aliases maps a local name to one or more destinations, which may be local users, remote addresses, a file, or a command via a pipe. The text file is only the source: `newaliases` (equivalent to `sendmail -bi`, and to `postalias /etc/aliases` under Postfix) compiles it into the indexed map the MTA queries at delivery time. A conventional entry every system should have is `root: someadmin`, so root's mail reaches a human.
Where this comes from
- Cited
- LPI exam objective 108.3
- What it says
- Create e-mail aliases and rebuild the alias database.
Practise this
Reading one question is not practice. The trainer will draw a set from objective 108 and space the ones you get wrong.