Don't halt boot if loopback mount fails

I mount the installation DVD image for my distribution with loopback mount so that I don't have to download packages if they are on the ISO image and up to date. To do this I have a line in /etc/fstab that looks like this:

/home/data/software/opensuse/openSUSE-Leap-42.2-DVD-x86_64.iso /srv/www/htdocs/42.2 iso9660 auto,ro,loop

The problem with this is that if for some reason the mount fails, say the ISO file has been renamed, or somehow the directory of the image or mountpoint are inaccessible, the boot process fails.

Enter the nofail option of systemd.mount. If the line is changed to this:

/home/data/software/opensuse/openSUSE-Leap-42.2-DVD-x86_64.iso /srv/www/htdocs/42.2 iso9660 auto,ro,loop,nofail,x-systemd.device-timeout=10

this prevents failure to mount from affecting the boot process. The problem can then be investigated after the machine has started up. The option x-systemd.device-timeout=10 specifies a shorter timeout than the default.

cd to directory containing a file

Many times I have run a program on a file and then immediately, wanted to change to the directory containing it, to do more operations. For example:

vim path/to/some/dir/file

then I next want to do:

cd path/to/some/dir

I used to do

cd !$

and then use the up arrow key to get the previous failed command to edit out the trailing filename and re-execute. Then I decided I should write a shell alias or function to do this. It has to be an alias or a function and not a script as cd needs to work in the current shell.

This is what I came up with:

cdf() { cd ${1%/[^/]*}; }

This uses the remove matching suffix operation of parameter substitution, see the bash manual page for details. So now I can do:

cdf !$

and I will end up in the directory containing the file I just worked on.

I picked cdf as an abbreviation for change to directory of file, but you may prefer some other name.