podman-container-tools/podman · error

failed to allocate ps argv

Error message

failed to allocate ps argv

What it means

C helper behind 'podman top': create_argv() (called from podmanTopInner in libpod/container_top_linux.go:133) mallocs (len+1) char* slots for the argv of the ps command and exits 255 (special_exit_code, kept in sync with the Go side) when malloc returns NULL. len is the number of ps arguments: the ps binary path plus every ps option/descriptor passed to 'podman top'. A NULL return means the reexec'ed podman process could not allocate memory — real OOM, a tiny RLIMIT_AS, or an absurd argument count.

Solutions

1. Retry 'podman top' without extra ps options (fewer arguments, smaller allocation)
2. Raise the memory limit on the podman process's cgroup (systemd MemoryMax/arena) or ulimit -v
3. Free memory / check for OOM killer activity (dmesg | tail) and retry when pressure passes
4. If persistent, report upstream with 'podman info' — allocation size is only pointer-sized per ps arg, so failure indicates environment-level memory starvation

# Sanity-check process limits and arg count before sampling with podman top
#!/bin/sh
# 1. keep ps descriptor lists modest (each becomes an argv slot)
[ $# -le 32 ] || { echo 'too many top descriptors' >&2; exit 1; }
# 2. make sure the calling context is not memory-starved
ulimit -v 2>/dev/null | grep -qv unlimited || true
v=$(ulimit -v 2>/dev/null || echo unlimited)
[ "$v" = unlimited ] || [ "$v" -gt 65536 ] || { echo "ulimit -v too low: $v" >&2; exit 1; }
exec podman top "$@"

When it happens

Trigger: 'podman top CTOR [ps options...]' on a host where the reexec'ed helper is under a cgroup memory limit or ulimit -v that the small malloc exceeds; passing an enormous number/column list of ps descriptors; fork/exec under severe memory pressure. The error appears on stderr of 'podman top' and the command exits 255.

Common situations: cgroups v2 memory.max set very low (systemd slices like MemoryMax=10M); heavy swap exhaustion; scripts looping 'podman top' with long -o column lists; ulimit -v inherited from a restricted service unit.

Related errors

• cannot read argv: %m
• cannot write to file descriptor: %m
• execve: %m
• fork: %m
• malloc: %m

AI-assisted analysis of podman-container-tools/podman@a2409076ef (2026-08-15). Data as JSON: /api/errors/b4f53252b6cdd708. Report an issue: GitHub.

Appendix: source

Thrown at libpod/container_top_linux.c:26

#include <stdio.h>
#include <stdlib.h>
#include <sys/mount.h>
#include <sys/wait.h>
#include <unistd.h>

/* keep special_exit_code in sync with container_top_linux.go */
int special_exit_code = 255;
int join_userns = 0;
char **argv = NULL;

void
create_argv (int len)
{
  /* allocate one extra element because we need a final NULL in c */
  argv = malloc (sizeof (char *) * (len + 1));
  if (argv == NULL)
    {
      fprintf (stderr, "failed to allocate ps argv");
      exit (special_exit_code);
    }
  /* add final NULL */
  argv[len] = NULL;
}

void
set_argv (int pos, char *arg)
{
  argv[pos] = arg;
}

void
set_userns ()
{
  join_userns = 1;
}

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