Sysadmins have many tools to view and manage running processes: top, atop, and htop. All of these tools monitor CPU and memory usage, and most of them list information about running processes Glances, also monitors filesystem I/O, network I/O, and sensor readouts that can display CPU and other hardware temperatures as well as fan speeds and disk usage by hardware device and logical volume.
To start Glances on a Linux host, open a terminal session and enter the command glances. Glances has three main sections—Summary, Process, and Alerts—as well as a sidebar. I'll explore them and other details for using Glances now.
The Summary section above provides an overview of the system's status. The first line shows the hostname, the Linux distribution, the kernel version, and the system uptime.
The next four lines display CPU, memory usage, swap, and load statistics. The left column displays the percentages of CPU, memory, and swap space that are in use. It also shows the combined statistics for all CPUs present in the system.
The Memory portion of the Summary section contains statistics about memory usage.
Glances usually determines the default sort column automatically. Processes can be sorted automatically (a), or by CPU (c), memory (m), name (p), user (u), I/O rate (i), or time (t). Processes are automatically sorted by the most-used resource. In the images above, the TIME+ column is highlighted.
Glances also shows warnings and critical alerts, including the time and duration of the event, at the bottom of the screen. This can be helpful when you're attempting to diagnose problems and cannot stare at the screen for hours at a time. These alert logs can be toggled on or off with the l (lower-case L) key, warnings can be cleared with the w key, while alerts and warnings can all be cleared with x.
The Process section displays standard information about each process that is running. Depending upon the viewing mode and the size of the terminal screen, different columns of information will be displayed for the running processes. The default mode with a wide-enough terminal displays the columns listed below. The columns that are displayed change automatically if the terminal screen is resized. The following columns are typically displayed for each process from left to right.