Locate vs mlocate – Key Differences Explained

locate

I wanted to install the command locate, which is available via sudo apt-get installmlocate.

However, I first ran sudo apt-get installlocate which seems to have installed something else.

Typing the command locate <package> however seems to call upon mlocate.

What is the package locate, and can (should) it be safely removed?

Best Answer

The locate package is the implementation of locate from GNU findutils. The mlocate package is another implementation of the same concept called mlocate. They implement the same basic functionality: quick lookup of file names based on an index that's (typically) rebuilt every night. They differ in some of their functionality beyond basic usage. In particular, GNU locate builds an index of world-readable files only (unless you run it from your account), whereas mlocate builds an index of all files but only lets the calling user see files that it could access. This makes mlocate more useful in most circumstances, but unusable in some unusual installations where it isn't run by the system administrator (because mlocate has to be setuid root), and a security risk.

Under Debian and derivatives, if you install both, locate will run the mlocate implementation, and you need to run locate.findutils to run the GNU implementation. This is managed through alternatives. If you have both installed, they'll both spend time rebuilding their respective index, but other than that they won't conflict with each other.

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Locate specific folders

Try this:

locate -r "wordpress-seo$"

Although i should mention that find offers huge variations of options over locate. You have found locate faster because it just reads from a database /var/lib/mlocate/mlocate.db while find search through files every time, whenever you give it something to search.

locate's database is updated by cron on a daily basis, you can also update the database manually anytime by:

sudo updatedb

This will make the files created after the daily cron update available in the locate database, so you will find those via locate. Also check the configuration file /etc/updatedb to see which filesystems, paths are being excluded.

No output from locate command

The problem was the permissions for / (the root directory) and the clue for finding that was this line from your strace output:

access("/", R_OK|X_OK)                  = -1 EACCES (Permission denied)

You were missing group read permission settings for /. But because you still had x (execute) permission, which allows you to traverse a directory, you could still access all of the files on the filesystem, which is why most everything continued working while those permissions were in effect. The only thing you were not allowed to do is list the contents of /. Most commands don't need to list /, they either use pathnames relative to the current directory or absolute pathnames that access specific well-known directories off the root (like /etc and /var).

For security reasons, locate, even though it has access to a complete inventory of filenames generated by a privileged user, insists on reporting only results that the calling user would be able to find by scanning the whole filesystem from the root. Since you couldn't list /, which makes scanning anything straight from the root a non-starter, locate would report nothing at all.

Best Answer

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Locate specific folders

No output from locate command

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