RFE: check for environment variables' existence in fstab

[kcgthb]

Hi!

The Image Format allows using environment variables from the host in the fstab specification:

References to environment variables from the host of the form ${ENVVAR} will be substituted.

This is great, but it could lead to errors when those environment variables are not defined. Typically, like this:

$ enroot start image echo ok
enroot-mount: failed to mount: none at /tmp/.enroot/data/image/none: No such file or directory

This is because when $VAR is undefined, a fstab like

${VAR}            ${VAR}   none    x-create=dir,bind,rw,nosuid

will result in just none x-create=dir,bind,rw,nosuid being passed to enroot-mount.

The parsing of those environment variables is done via awk in common::envsubst() (common.sh), so usual bash substitution can't be used there (like for instance ${VAR:-#}).

Since it's not really possible to make the .fstab files in mounts.d/* conditional or select/disable them at run time, would it be possible to add a test to prevent undefined environment variables in .fstab files from generating mounting errors?

Thanks!

[3XX0]

The mount file format is really basic, I would suggest you use hooks if you need conditional logic

[kcgthb]

Ah yes, using hooks for conditional mounts makes perfect sense, thanks for the suggestion!