After a recent Windows 10 security update, the cygwin installation stopped working, as mintty was unable to fork bash. The last time this happened, none of the nostrums on the internet had worked, and a complete re-install was required. However, this time I had an alternative, Windows Subsystem for Linux (WSL).
I'd been watching its progress for a while and now that, in the Fall Creator's Update, the use of network shares had been enabled, it seemed to have the features I needed.
First, you have to turn on WSL via the Settings->Apps & Features->Related Settings (Programs and Features)->Turn Windows Features on or off and tick the box labelled Windows Subsystem for Linux. A reboot will be required.
Once enabled, I discovered that Debian was now available for WSL - much better than Ubuntu. Installing was a matter of moments from the Microsoft Store. Pretty much all the configuration information it needs is a user name.
Now, I needed a decent terminal emulator to front it. It turns out that mintty has been forked for WLS, named wsltty (natch). This was also a simple install.
Once fired up, I was presented with a bash prompt. The first things to do were to
sudo apt-get update sudo apt-get upgrade sudo apt-get install python ssh rsync mg
mg is a lightweight terminal-only version of emacs, which I
prefer to use rather than vim, which is included.
Linux-based editing tools are necessary because you must not edit Linux
files with Windows tools, as the Windows tools do not handle the
Linux file metadata. See this graphic
warning.
NOTE: Things have changed recently. See these
chmod improvements. Furthermore, automount options can be
specified in /etc/wsl.conf. See this.
However, the WSL version I have doesn't contain these capabilities.
My first (and presumably not the last) footshooting incident occured
when I edited the /etc/sudoers file in an attempt to remove
the need for entering a password when running sudo. The result was
that I introduced a syntax error and sudo cried out in horror and
refused to run. Now what? Advice on the internet either involved
tools that did not exist on the WSL Debian install, or required
booting into single user mode. However, there is a simple
workaround. It is possible to set the default user name when WSL is
started. The normal default is the user name entered as part of the
installation.
I figured I could change the default user to root (hopefully no
password required) and fix the syntax error. The debian
executable is located in
C:\Users\mark\AppData\Local\Microsoft\WindowsApps.
debian config --default-user root
I restarted Debian and was in as root. Foot unshot.
To make the WSL enviroment comfortable, I wanted to have my Windows home
directory be the Debian home directory. By default, the home
directory for the default user is under /home, as one would
expect. Initially, I tried making /home/mark a soft link
to /mnt/c/Users/mark/home. This worked, but then the ssh
client was unable to use my certs, as it is not possible to set the
file permissions on a file in the Windows file system as ssh
expects, due to above file metadata issues.
The compromise I made was to leave /home/mark as my home
directory in /etc/passwd, then place the
.bash_profile file, plus the .ssh directory in
/home/mark. In /home/mark/.bash_profile, I set the HOME
variable to the Windows home location:
export HOME=/mnt/c/Users/mark/home
This seems to do what I need. Bash thinks my Windows home is my WSL
home and the ssh client is still using /home/mark/.ssh to
access the certs, as it ignores the value of $HOME value and
directly accesses /etc/passwd.
The last useful piece of setup was related to the ability to
right-click in a folder window and invoke bash with the folder as
the current working directory. This involves setting up Windows
registry entries to add the appropriate menu items. wsltty
provides scripts for to put the entries in the Windows registry.
However, subverting the default rcfile name was the only way I could
find to make bash behave as a login shell and still use the selected
folder as the current directory.
%LOCALAPPDATA%\wsltty\bin\mintty.exe --WSL="Debian" \
--configdir="%APPDATA%\wsltty" /bin/bash --rcfile /home/mark/.bash_profile
Network shares can be mounted like this:
sudo mount -t drvfs '\\crimson\public' /mnt/share/crimson/public
I tried using rsync to synchronise my home directory to a directory on the share. Even with nothing to update, it took 4 minutes 30 seconds. By contrast, rsync under cygwin, also with no updates required, took 49 seconds. I/O through drvfs must be very inefficient.
