The tmpfs plugin allows you to mount a tmpfs on the chroot dir. This plugin is disabled by default.

Configuration

You can enable the plugin using this settings:

config_opts['plugin_conf']['tmpfs_enable'] = True
config_opts['plugin_conf']['tmpfs_opts'] = {}
config_opts['plugin_conf']['tmpfs_opts']['required_ram_mb'] = 1024
config_opts['plugin_conf']['tmpfs_opts']['max_fs_size'] = '768m'
config_opts['plugin_conf']['tmpfs_opts']['mode'] = '0755'
config_opts['plugin_conf']['tmpfs_opts']['keep_mounted'] = False

• required_ram_mb - If system has less memory than this value, the Tmpfs plugin is disabled and a warning is omitted, but mock will continue.
• max_fs_size - this is passed to mount.tmpfs as -o size=X
• mode - this is passed to to mount.tmpfs as -o mode=X
• keep_mounted - when set to True, the buildroot is not unmounted when mock exits (which will destroy it’s content). Additionally when mock is starting and it detects the tmpfs from a previous run, it will reuse it.

You can not combine Tmpfs plugin and Lvm_root plugin, because it is not possible to mount Logical Volume as tmpfs.