/etc/localtime is already a symbolic link to a zoneinfo file, and `ln -s /usr/share/zoneinfo/Europe/Berlin /etc/localtime` fails because the destination exists. Which command replaces the link in one step?
LPIC-1 Exam 101-500, objective 104. Devices, Linux filesystems, filesystem hierarchy standard medium
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The options
Correct ln -sf /usr/share/zoneinfo/Europe/Berlin /etc/localtime
Correct. -f removes an existing destination before creating the new link, which is what turns the failure into a replacement.
Not correct ln -sv /usr/share/zoneinfo/Europe/Berlin /etc/localtime
Wrong. -v only makes ln report each link it creates. It changes nothing about the refusal to overwrite.
Not correct ln -sr /usr/share/zoneinfo/Europe/Berlin /etc/localtime
Wrong. -r stores the target as a path relative to the link's own directory rather than as an absolute path. The destination still exists, so the command still fails.
Not correct ln -sT /usr/share/zoneinfo/Europe/Berlin /etc/localtime
Wrong. -T forces the destination to be treated as an ordinary file rather than as a directory to create the link inside. Without -f it still refuses to overwrite.
Why
ln will not clobber an existing destination unless told to; -f unlinks it first. There is a trap worth remembering alongside it: if the existing destination is a symbolic link to a directory, ln -sf follows it and drops the new link inside that directory instead of replacing the link. Adding -n (or -T) stops that dereference, which is why the safe idiom for repointing a directory symlink is ln -sfn.
Where this comes from
- Cited
- manual page ln(1)
Practise this
Reading one question is not practice. The trainer will draw a short set from objective 104 and space the ones you get wrong.
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