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84eff9ef3b
closes: #27411
Adjust SUB_UID and SUB_GID ranges to support running rootless Podman inside a rootless run Podman container.
Also add a test to verify the change and prevent regression.
By default, a new user is assigned the following sub-ID ranges:
SUB_UID_MIN=100000, SUB_GID_MIN=100000, SUB_UID_COUNT=65536, SUB_GID_COUNT=65536
This means the user’s sub-UID and sub-GID ranges are 100000–165535.
When the container is run rootless with the user defined below, ID mappings occur as follows:
- Container ID 0 (root) maps to user ID 1000 on the host (which is the user created below).
- Container IDs 1–65536 map to IDs 100000–165535 on host (the subid range previously mentioned).
If a new user is created inside this container (to build containers for example), it will
attempt to use the default sub-ID range (100000–165535). However, this exceeds the container’s
available ID mapping, since only IDs up to 65536 are mapped. This causes nested rootless Podman
to fail.
To enable container-in-container builds, the sub-ID ranges for the user must be large enough
to provide at least 65536 usable IDs. A minimum SUB_UID_COUNT and SUB_GID_COUNT of 165536 is
required, but 1,000,000 is used here to provide additional margin.
1,000,000 matches the subid range other machines are using, defined in [ignition.go](69b397af49/pkg/machine/ignition/ignition.go (L284-L289)).
The script of other machines modify the subid files directly for 1 user, the `sed` command used in
this fix mimics that.
The test is added as en extension to the 'simple init with username' test case, to prevent having
to create a new VM.
Signed-off-by: dvorst <87502756+dvorst@users.noreply.github.com>