You must duplicate /srv/www to /srv/www.bak so that the copy keeps every file's ownership, permissions and timestamps, recurses into subdirectories, and stores symbolic links as links rather than as copies of their targets. Which command does all of that?
LPIC-1 Exam 101-500, objective 103. GNU and Unix commands medium
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How these questions are written — where each question comes from, what the verification ledger records, and what happens when one is found wrong.
The options
Correct cp -a /srv/www /srv/www.bak
Correct. -a is the archive option: it recurses, never dereferences symbolic links, and preserves as much of the metadata as possible — mode, ownership, timestamps and, where supported, ACLs and extended attributes.
Not correct cp -r /srv/www /srv/www.bak
Wrong in one respect. -r does recurse, but the copies are new files owned by the invoking user with fresh modification times, so ownership and timestamps are lost.
Not correct cp -p /srv/www /srv/www.bak
Wrong. -p preserves mode, ownership and timestamps but does not recurse, so cp refuses the directory with a message saying it was omitted.
Not correct cp -u /srv/www /srv/www.bak
Wrong. -u copies only when the source is newer than the destination, or the destination is missing. It is an update rule, and on its own it does not recurse either.
Why
cp -a is shorthand for -dR --preserve=all: -R to recurse, -d to keep symbolic links as symbolic links, and full metadata preservation. It is the option to reach for whenever a copy must be indistinguishable from the original. Preserving ownership requires privilege, so an unprivileged user gets a warning for files they do not own.
Where this comes from
- Cited
- manual page cp(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 103 and space the ones you get wrong.
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