Linux SIGQUIT

SIGQUIT is a termination signal sent to a process, typically triggered by the user pressing Ctrl+\ or via the kill command. It causes the process to terminate and generate a core dump for debugging purposes.

Common Causes

User pressing Ctrl+\ in the terminal
Explicit kill command: kill -3 <PID> or kill -SIGQUIT <PID>
Process receiving SIGQUIT from another application or system component
Container runtime sending SIGQUIT before forceful termination

How to Fix

1 Check Process Status and Core Dumps

Verify if the process terminated and check for generated core dump files for debugging.

BASH

 $ # Check process status
ps aux | grep <process_name>

# Look for core dump files (location may vary)
ls -la /var/lib/systemd/coredump/
ls -la /tmp/
find / -name "core*" -type f 2>/dev/null | head -20

2 Configure Core Dump Settings

Ensure core dumps are enabled and properly configured to capture debugging information.

BASH

 $ # Check current core dump limits
ulimit -c

# Set unlimited core dump size for current session
ulimit -c unlimited

# Permanent configuration in /etc/security/limits.conf
# Add: * soft core unlimited
# Or user-specific: username soft core unlimited

3 Debug with GDB Using Core Dump

Use GDB to analyze the core dump file and understand why the process received SIGQUIT.

BASH

 $ # Debug with core dump
gdb /path/to/executable /path/to/core.dump

# Once in GDB, run these commands:
# bt - show backtrace
# info registers - show register values
# info threads - show all threads
# thread apply all bt - backtrace for all threads

4 Handle SIGQUIT in Application Code

Implement signal handlers in your application to gracefully handle SIGQUIT instead of terminating.

BASH

 $ // C/C++ example signal handler
#include <signal.h>
#include <stdio.h>
#include <stdlib.h>

void sigquit_handler(int sig) {
    printf("Received SIGQUIT. Performing cleanup...\n");
    // Perform cleanup operations
    fflush(stdout);
    exit(0); // Exit gracefully
}

int main() {
    signal(SIGQUIT, sigquit_handler);
    // Your application code here
    while(1) {
        // Main loop
    }
    return 0;
}

5 Prevent Accidental Ctrl+\ Triggers

Configure terminal or shell to ignore or remap Ctrl+\ key combination.

BASH

 $ # Disable Ctrl+\ in bash
stty quit undef

# Or remap to another key
stty quit ^x  # Change to Ctrl+x

# Make permanent in ~/.bashrc
echo 'stty quit undef' >> ~/.bashrc