PACKER_LOG=1
enables logging output. Pipe with 2>&1 | tee packer.log
to a file.
$ pve_user=root@pam pve_pass=s3cr3t pve_url=https://pve.domain.tld:8006/api2/json packer build -only=proxmox -var-file=vars/pve.json build.json
...might hit me on ubuntu as well.
$ ulimit -a # show value of file descriptors
-t: cpu time (seconds) unlimited
-f: file size (blocks) unlimited
-d: data seg size (kbytes) unlimited
-s: stack size (kbytes) 8192
-c: core file size (blocks) 0
-v: address space (kbytes) unlimited
-l: locked-in-memory size (kbytes) unlimited
-u: processes 1418
-n: file descriptors 256
$ ulimit -n 4096 # set new value, temporary for this session
This fixes the error "socket: too many open files" or "tcp: lookup: no such host"