[Error] Hitting thread / process resource limits in systemd container

[sir-yells-alot]

Description
Trying to create more than ~400 processes / threads fails

To Reproduce

distrobox create --name test --init --image quay.io/archlinux/archlinux:latest --additional-packages "systemd"
distrobox enter test
for i in {1..400} ; do ( sleep 1 & ); done

Error:
bash: fork: retry: Resource temporarily unavailable

Expected behavior
Bash does not fail to create more than ~400 processes

Logs
distrobox-test.log
podman-logs.log

Desktop:
Using podman version 4.9.0
Using distrobox version 1.6.0.1
On: NixOS 24.05 (Uakari) & unstable packages
Distrobox was installed with the installation scripts into ~/.local

Additional context
I'm not entirely sure if it is resource limits, but it seems to have something to do with the distrobox enter command putting your shell in init.scope

[siryellsalot@test ~]$ systemctl status
● test.gengar
    State: running
    Units: 554 loaded (incl. loaded aliases)
     Jobs: 0 queued
   Failed: 0 units
    Since: Thu 2024-02-01 22:26:37 UTC; 11min ago
  systemd: 255.3-1-arch
   CGroup: /
           ├─init.scope
           │ ├─   1 /usr/lib/systemd/systemd --system --log-target=console --unit=multi-user.target
           │ ├─ 951 script -c "cat /var/console" /dev/null
           │ ├─ 954 cat /var/console
           │ ├─1045 /usr/sbin/bash -l
           │ ├─1939 /usr/sbin/bash -l
           │ ├─1949 systemctl status // <- status command and shell is here
           │ └─1950 less
           ├─system.slice
// you get the idea ...

However using machinectl to make systemd start a shell for you works around this issue:

[siryellsalot@test ~]$ for i in {1..400} ; do ( sleep 1024 & ); done
[siryellsalot@test ~]$ systemctl status
● test.gengar
    State: running
    Units: 563 loaded (incl. loaded aliases)
     Jobs: 0 queued
   Failed: 0 units
    Since: Thu 2024-02-01 22:26:37 UTC; 20min ago
  systemd: 255.3-1-arch
   CGroup: /
           ├─init.scope
           │ ├─   1 /usr/lib/systemd/systemd --system --log-target=console --unit=multi-user.target
           │ ├─ 951 script -c "cat /var/console" /dev/null
           │ ├─ 954 cat /var/console
           │ ├─1045 /usr/sbin/bash -l
           │ ├─1939 /usr/sbin/bash -l
           │ ├─1951 sudo machinectl shell siryellsalot@.host
           │ ├─1952 sudo machinectl shell siryellsalot@.host
           │ ├─1953 machinectl shell siryellsalot@.host
           │ ├─2780 /usr/sbin/bash -l
           │ ├─2790 systemctl status
           │ └─2791 less
           ├─system.slice
           │ ├─dbus-broker.service
           │ │ ├─1050 /usr/bin/dbus-broker-launch --scope system --audit
           │ │ └─1057 dbus-broker --log 4 --controller 9 --machine-id a33d0612fca8459588a9801705f6f80e --max-bytes 53687>
           │ ├─systemd-journald.service
           │ │ └─1019 /usr/lib/systemd/systemd-journald
           │ ├─systemd-logind.service
           │ │ └─1058 /usr/lib/systemd/systemd-logind
           │ └─systemd-machined.service
           │   └─1954 /usr/lib/systemd/systemd-machined
           └─user.slice
             ├─user-1000.slice
             │ ├─session-3.scope
             │ │ ├─1955 /usr/sbin/bash -l <- new shell is here
             │ │ ├─1981 sleep 1024
             │ │ ├─1983 sleep 1024
             │ │ ├─1985 sleep 1024
// sleeping beauty be like: 

This doesn't work to fix the my original use case, which was to use VsCode + Platform IO (that hit the limit) because``machinectl shell``` discards all stuff that distrobox does to integrate with host.
Any ideas?
The workaround also only raises the limit to somewhere around 660 however that should still be enough

[89luca89]

Hi @sir-yells-alot pushed a fix for it now, and seems to work correclty: