updatedb

Understanding updatedb

The updatedb command is an important component of the locate command’s functionality. locate doesn’t search your entire filesystem every time you use it; instead, it queries a database of file paths. updatedb is responsible for creating and updating this database. This database typically resides at /var/lib/mlocate/mlocate.db.

Without regular updates using updatedb, the locate command will return outdated results, missing newly created or moved files.

Using updatedb

The basic usage of updatedb is remarkably straightforward:

sudo updatedb

The sudo is necessary because updatedb needs root privileges to access the entire filesystem. Running this command will rebuild the mlocate.db database, indexing all files within your system. This process can take some time, depending on the size of your file system.

updatedb Options

While the basic command is sufficient for most users, updatedb offers a few options for fine-tuning the update process:

• -V or --verbose: This option provides verbose output, showing the progress of the database update. This is useful for monitoring the process and identifying potential issues.

sudo updatedb -V

• -U or --update: This option only updates the database with changes since the last update. This is faster than a full rebuild (updatedb) and is ideal for incremental updates. However, for a clean update, using updatedb is recommended once in a while.

sudo updatedb -U

• -o <database>: This option allows you to specify a different database file. The default is /var/lib/mlocate/mlocate.db. This is rarely needed but can be useful in specialized scenarios.

sudo updatedb -o /tmp/my_locate_db  #Creates database in /tmp folder.  Remember to change permissions appropriately.

Integrating updatedb into Cron Jobs

For automatic updates, you can schedule updatedb to run regularly using a cron job. This ensures your locate database remains consistently up-to-date. Edit your crontab file using crontab -e and add a line similar to this to run the update daily at 3 AM:

0 3 * * * sudo updatedb -U

This line uses the -U option for efficient incremental updates. Remember to adjust the time and frequency to suit your needs. You could run it weekly or even less frequently, depending on the rate of file changes on your system.

Troubleshooting

If updatedb fails, check the system logs (/var/log/syslog or similar) for error messages. Common causes include permission issues or insufficient disk space. Ensure the mlocate package is installed using your distribution’s package manager (e.g., apt-get install mlocate on Debian/Ubuntu, yum install mlocate on CentOS/RHEL). In some cases, you might need to manually delete the old database file before running updatedb. However, this is a last resort and only after thorough investigation and backup of relevant data, if necessary.