Linux /proc and Process Debugging

tr "\0" " " < /proc/1234/cmdline; echo

# Print the null-separated command line from /proc.

tr "\0" "
" < /proc/1234/environ | head

# Inspect environment variables of a process when permitted.

ls -l /proc/1234/fd | head

# Inspect file descriptors directly from procfs.

cat /proc/1234/limits

# Display RLIMIT values for a process.

head -40 /proc/1234/maps

# Inspect mapped memory regions and permissions.

head -80 /proc/1234/smaps

# Inspect detailed per-region memory accounting.

sudo cat /proc/1234/stack

# Inspect a sleeping task kernel stack when permitted.

cat /proc/1234/sched | head -40

# Inspect scheduling statistics and vruntime data.

strace -o trace.log ./program

# Trace syscalls made by a new command.

sudo strace -p 1234

# Attach to a live process and trace syscalls.

strace -ff -o trace ./server

# Write one trace file per process and follow forks.

strace -e trace=network -p 1234

# Focus on network-related system calls only.

strace -e trace=file -p 1234

# Focus on file and pathname operations.

ltrace -o ltrace.log ./program

# Trace dynamic library calls if ltrace is installed.

sudo perf top

# Sample hot functions on the system in real time.

sudo perf record -p 1234 -- sleep 30

# Collect CPU samples for one PID over time.

sudo perf report

# Analyze a perf recording interactively.

gdb -p 1234

# Attach a debugger to a running process.

gdb -batch -ex "thread apply all bt" -p 1234

# Collect all-thread backtraces from a live process.

coredumpctl list

# List core dumps managed by systemd-coredump.

coredumpctl gdb 1234

# Load the newest core dump for a PID into gdb.

ulimit -c unlimited

# Allow the shell to generate core dumps.