qemu runner: define static mount tag for mount_cache#2023
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89luca89 merged 1 commit intoJun 3, 2025
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In 2c1640e ("fix: handle CACHEDIR properly (chainguard-dev#2021)"), the qemu runner was changed to mount the host's melange-cache into the vm as a disk based overlayfs. However, when it does this, it set the mount_tag that the 9p client in the guest uses to identify what to mount as the path in the host system, based on $TMPDIR. Unfortunately, the mount_tag has a limit of 31 characters, so if $TMPDIR is set to not /tmp, this can cause failures, like it did for me: ``` WARN qemu: qemu-system-x86_64: -device virtio-9p-pci,id=fs101,fsdev=fsdev101,mount_tag=/home/sbeattie/tmp/melange-cache: mount tag '/home/sbeattie/tmp/melange-cache' (32 bytes) is longer than maximum (31 bytes) ERRO failed to build package: unable to start pod: qemu: VM exited unexpectedly: exit status 1 ``` To fix this, convert the mount_tag for the melange cache in the qemu invocation to a static tag called "melange_cache", and pass that in the 9p mount invocation. Signed-off-by: Steve Beattie <steve.beattie@chainguard.dev>
89luca89
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Jun 3, 2025
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In 2c1640e ("fix: handle CACHEDIR properly (#2021)"), the qemu runner was changed to mount the host's melange-cache into the vm as a disk based overlayfs. However, when it does this, it set the mount_tag that the 9p client in the guest uses to identify what to mount as the path in the host system, based on $TMPDIR. Unfortunately, the mount_tag has a limit of 31 characters, so if $TMPDIR is set to not /tmp, this can cause failures, like it did for me:
To fix this, convert the mount_tag for the melange cache in the qemu invocation to a static tag called "melange_cache", and pass that in the 9p mount invocation.