dnf --installroot documentation needs updating for newer Fedora and DNF

[DCKcode]

Currently Buildah's documentation mentions two examples where dnf --installroot is used to generate a rootfs for Buildah:

• The buildah unshare manpage
• The tutorial
• A demo script

Best I can tell this still works on EL9, EL10 as well as Fedora 40 and below. However, trying these on Fedora 41+, these commands don't actually work. Presumably this is because Fedora 41+ have switched to DNF5, which is not fully backwards compatible with earlier versions of DNF.

In my testing I needed to at least add the option --use-host-config to my dnf invocation to reproduce these commands on Fedora 41. That itself would be an easy fix, but I noticed at least on some Fedora 41 variants an additional workaround is necessary when attempting to do the rootless install the buildah unshare documentation describes. I'm not sure that's a workaround that'd be appropriate to include in documentation, or whether that points to an issue elsewhere.

[tanwald]

I cannot build images from scratch since Fedora 42.

I used the following within a script that I run with buildah unshare:

dnf install \
    --use-host-config \
    --releasever 42 \
    --assumeyes \
    --noplugins \
    --nodocs \
    --setopt countme=false \
    --setopt install_weak_deps=0 \
    $PKGS

Since Fedora 42 I get the following errors:

>>> Finished pre-transaction scriptlet: filesystem-0:3.18-36.fc42.x86_64                                                                                                                                                                                                         
>>> [RPM] Unable to get systemd shutdown inhibition lock: Did not receive a reply. Possible causes include: the remote application did not send a reply, the message bus security policy blocked the reply, the reply timeout expired, or the network connection was broken.    
...
>>> Running sysusers scriptlet: setup-0:2.15.0-13.fc42.noarch                                                                                                                                                                                                                    
>>> Error in sysusers scriptlet: setup-0:2.15.0-13.fc42.noarch                                                                                                                                                                                                                   
>>> [RPM] %sysusers(setup-2.15.0-13.fc42.noarch) scriptlet failed, exit status 127                                                                                                                                                                                               
[10/72] Installing filesystem-0:3.18-36.fc42.x86_64                                                                                                                                                                                      100% |   1.7 MiB/s | 212.4 KiB |  00m00s
>>> [RPM] setup-2.15.0-13.fc42.noarch: install failed                                                                                                                                                                                                                            
>>> [RPM] failed to open /etc/group for id/name lookup: No such file or directory                                                                                                                                                                                                
>>> [RPM] group mail does not exist - using root  
...
Transaction failed: Rpm transaction failed.

Adding --setopt persistdir=$(mktemp -d) did not help.

[rhatdan]

Looks like the install is trying to communicate with systemd?

Could you try this in rootful mode?