About

This is a data protection wrapper for mkfs.X tools. Generally speaking, it can be used with any tool of calling signature tool [options] target, where the target is either a block device or some raw image file (accepted filename extensions: bin, disk, img, part, raw).

Among mkfs.X tools there are smart and dumb ones.

Smart tools check if the target contains something before doing anything. In the case, some tools ask for confirmation (e.g. the mkfs.ext family), while others refuse to proceed (e.g. mkfs.xfs).

Dumb tools just format the target without any checks (e.g. mkfs.fat).

This script makes those dumb tools safer to use by emulating the smart behavior. It relies on libblk for the check, just like the mkfs.ext family does.

Notice: The smart behaviour is only emulated when you run the script on a terminal. The mkfs.ext family does the same to not break existing scripts (quoted from mke2fs.c).

Notice: Some mkfs.X tools accept an extra non-option argument: filesystem size. This script does not support that, it assumes the last argument is the target.

Notice: Some mkfs.X tools can create the fs starting at some offset (e.g. mkfs.fat with its --offset option). This script does not parse any options, it just assumes the last argument is the target as-is.

Setup

There are two ways to use the script:

• standalone mode: when called as ifempty tool ... It is easier to install but you have to manually prepend ifempty each time
• symlink mode: when you override your tools with symlinks to ifempty and call them like you always do with just tool ..

In any case:

• save the script as /usr/local/bin/ifempty and make it executable

Extra steps for the symlink mode:

• check if /usr/local/sbin is in your PATH and overrides /usr/sbin
• in /usr/local/sbin, create symlinks for the dumb tools, pointing to /usr/local/bin/ifempty

Example for the standalone mode

> ifempty mkfs.fat disk.img
'disk.img' contains some GPT partition table
Proceed anyway? (y,N) n
> ifempty mkfs.fat part1.img
'part1.img' contains some XFS superblock
Proceed anyway? (y,N) n

Example for the symlink mode

> tree /usr/local/sbin
/usr/local/sbin
├── mkfs.exfat -> /usr/local/bin/ifempty
├── mkfs.fat -> /usr/local/bin/ifempty
├── mkfs.msdos -> /usr/local/bin/ifempty
└── mkfs.vfat -> /usr/local/bin/ifempty

> command -v mkfs.fat
/usr/local/sbin/mkfs.fat

> mkfs.fat disk.img
'disk.img' contains some GPT partition table
Proceed anyway? (y,N) n
> mkfs.fat part1.img
'part1.img' contains some XFS superblock
Proceed anyway? (y,N) n