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mmdebstrap-autopkgtest-build-qemu: add documentation of some unshare magic

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Johannes Schauer Marin Rodrigues 2024-03-23 22:49:27 +01:00
parent cdf6959a41
commit 9726836ac4
Signed by: josch
GPG key ID: F2CBA5C78FBD83E1
1 changed files with 4 additions and 1 deletions
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mmdebstrap-autopkgtest-build-qemu
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@ -308,12 +308,15 @@ FAT_SIZE_SECTORS=$((1024*254))
# - users who prefer qcow2 get to choose to run it themselves with their own # - users who prefer qcow2 get to choose to run it themselves with their own
# custom options like compression # custom options like compression
# #
# --map-users=auto --map-user=0 => 0:$UID:1 + 1:$SUBUIDBASE:65535
# --map-users=auto --map-user=65536 => 0:$SUBUIDBASE:65536 + 65536:$UID:1
#
# Make the image writeable to the first subgid. mmdebstrap will map this gid to # Make the image writeable to the first subgid. mmdebstrap will map this gid to
# the root group. unshare instead will map the current gid to 0 and the first # the root group. unshare instead will map the current gid to 0 and the first
# subgid to 1. Therefore mmdebstrap will be able to write to the image. # subgid to 1. Therefore mmdebstrap will be able to write to the image.
rm -f "$IMAGE" rm -f "$IMAGE"
: >"$IMAGE" : >"$IMAGE"
unshare -U -r --map-groups=auto chown 0:1 "$IMAGE" unshare --map-user=0 --map-group=0 --map-groups=auto chown 0:1 "$IMAGE"
chmod 0660 "$IMAGE" chmod 0660 "$IMAGE"
# Make sure that the unshared user is able to access the file. # Make sure that the unshared user is able to access the file.