How to Check Active Mount Points in Linux: Exploring mount and /proc/mounts

When managing a Linux system, understanding how storage devices are organized and accessed is crucial. Mount points act as crucial junctions where storage devices are made accessible to the system. Two essential tools that can help system administrators or curious users view the currently active mount points are the mount command and the contents of /proc/mounts. In this blog, we dive into how to utilize these resources for monitoring and managing mounted filesystems in Linux.

Understanding Mount Points

Before delving into tools and commands, let’s clarify what a mount point is. In Linux, a mount point is a directory (typically an empty one) in the directory structure where additional filesystems are mounted. When a filesystem is mounted to this directory, the user can access the files on the filesystem by navigating through this directory.

Using the mount Command

The mount command is versatile, widely used for mounting filesystems, and equally useful for displaying mount information. When executed without arguments, mount prints a list of all currently mounted filesystems, along with their mount points and some additional options. Here's how to use it:

1. Open your terminal.
2. Simply type mount and press Enter.

$ mount

This will output something like:

sysfs on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
proc on /proc type proc (rw,nosuid,nodev,noexec,relatime)
udev on /dev type devtmpfs (rw,nosuid,relatime,size=2016088k,nr_inodes=504022,mode=755)
/dev/sda1 on / type ext4 (rw,relatime,errors=remount-ro)
...

Each line provides detailed information about one mount point, including the device name, the mount point, the filesystem type, and mount options.

Exploring /proc/mounts

While mount offers an easy and straightforward way to view mount points, the /proc/mounts file provides a more direct approach by reading the kernel's view of the mount table. This method can be particularly useful for scripting or when you need a machine-parseable format. Here’s how to use it:

1. Open your terminal.
2. Use cat or another viewing command to display the contents of /proc/mounts:

$ cat /proc/mounts

You'll see output similar to what mount produces, but it's often more detailed and reflects the current state of the system mount points directly from the kernel's perspective:

rootfs / rootfs rw 0 0
sysfs /sys sysfs rw,nosuid,nodev,noexec,relatime 0 0
proc /proc proc rw,nosuid,nodev,noexec,relatime 0 0
udev /dev devtmpfs rw,nosuid,relatime,size=2016088k,nr_inodes=504022,mode=755 0 0
/dev/sda1 / ext4 rw,relatime,errors=remount-ro 0 0
...

Analyzing this file can give you a raw and unfiltered look at your system’s mounts.

Practical Uses of Mount Information

Knowing how to check active mount points is useful for various administrative tasks:

• Troubleshooting System Issues: If an application fails to access a particular directory, you might want to check if the filesystem is properly mounted.

• System Maintenance: Before a backup or a major update, it's essential to know which filesystems are active and if any external resources are mounted.

• Security Audits: Unintended or rogue mount points can be security risks, and regular checks can help tighten system security.

Conclusion

Whether you're a system administrator keeping tabs on the system’s health or a power user exploring your Linux setup, knowing how to effectively use mount and /proc/mounts to check active mount points is an essential skill. Both methods provide crucial insights and can be part of regular system checks or troubleshooting processes. Experiment with these tools, and you'll find managing your filesystems significantly easier!