captree - Linux

Overview

captree is a command-line tool used to capture and record the system boot process of Linux systems. It provides a detailed trace of the boot sequence, including kernel boot parameters, device initialization, and system services startup. captree is particularly useful for troubleshooting boot issues and performance analysis.

Syntax

captree [options]

Options/Flags

  • -b: Boot device. Specify the device from which the system boots.
  • -f: Filename. Name of the output file to save the boot trace. Defaults to captree.txt
  • -m: Monitor. Specifies the type of monitoring. Options include:
    • full: Captures the entire boot process.
    • preinit: Captures the process up to the initialization of system services.
    • postinit: Captures the process from the initialization of system services onward.
  • -o: Output format. Specify the format of the output trace. Options include:
    • text: Plain text format.
    • html: HTML format for easier readability.
  • -p: Print level. Sets the verbosity of the output. Options include:
    • 0: Minimal output.
    • 1: Normal output.
    • 2: Verbose output.
  • -r: Read-only mode. Only reads the boot trace from the specified file.
  • -s: Size. Limits the size of the output file in bytes.
  • -w: Wait time. Sets the timeout period in seconds before the process is automatically terminated.

Examples

Capture the entire boot process:

captree -m full -f boot.txt

Capture the boot process up to system service initialization:

captree -m preinit -f earlyboot.txt

Read a saved boot trace and display in HTML format:

captree -r -o html boot.txt

Common Issues

Permission Denied Errors:

  • Ensure that you have sufficient permissions to access the specified boot device or file.

Invalid Output Format:

  • Check that the specified output format is valid. captree supports text and HTML formats.

Integration

Combining captree with systemd:

  • captree can be integrated with systemd to automatically capture boot traces during system boots. Configure the following in /etc/systemd/systemd.conf.d/captree.conf:
[Service]
ExecStart=/usr/sbin/captree -m full -f /var/log/boot.txt

Related Commands

  • systemd-analyze
  • dmesg
  • journalctl