Troubleshooting: E Unable to Locate Package

Anyone tasked with maintaining Debian-based web servers knows how common it is to encounter errors regarding packages unable to be located. This issue can be caused by a variety of underlying causes, but the most common source is lack of appropriate authorizations for mounting packages to the intended computing environment. This post will explore how to troubleshoot the error “E: Unable to locate package,” which is often encountered when trying to install programs on Debian systems.

What is the cause of the issue?

At its root, this issue occurs because the package manager is unable to locate the requested package, even if the correct package name was specified in the install attempt. This often occurs because the package is not present in the list of repositories available on the computer, as specified by the file /etc/apt/sources.list. This file contains a comprehensive list of packages that the package manager will security look for in its install attempts.

The other main cause of this issue is a lack of mounting permissions, which often happens if the necessary packages have not been installed manually. In this case, the package manager is unable to read permissions for the mounts, meaning it is unable to install the target package. This issue is a common pitfall for systems administrators and can be solved through a combination of tinkering with mount permissions and adding the requested package to the relevant source list.

How to solve the issue

If your system encounters the error “E: Unable to locate package” while attempting an install, begin by double-checking that the correct package request was specified. Common typos, such as entering the incorrect version number, will sometimes trigger this error. Once you have confirmed the name of the package and version number, check that the package exists in the sources.list file. Taking a moment to review each of the repos listed in the /etc/apt/sources.list file may reveal that the desired package is not present in the database. If this is the case, you may need to manually download the package and install it in the appropriate repository, adding it to the sources.list before attempting another install.

If the package is present in the repository, the next step will be examining mount permissions. To do this, try the command “sudo mount -o remount,rw /” which can be used to ensure that the mount permissions of the mounted directories have read and write permissions. If this fails to generate output or reports of errors, you may need to look into manually resetting the mount permissions. You can use the command “mount -o remount,rw,user, ” to manually set the mount permissions.


When attempting to install packages on Debian systems, the error “E: Unable to locate package” can often be resolved with a combination of troubleshooting tactics. If the requested package is not present in the sources.list file, this can be remedied by manually downloading the package and adding it to the file, or tweaking the mount permissions of the mounted directories to ensure that they read and write permissions. By taking a methodical approach to troubleshooting, you can quickly identify and resolve the underlying cause of this issue.

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