Subject: Re: [bug#41259] [PATCH] etc: Add a systemd unit to bind-mount @storedir@ read-only.

From: Julien Lepiller <[email-masked]>
Date: Thu, 14 May 2020 14:49:15 -0400

Le 14 mai 2020 12:35:12 GMT-04:00, Julien Lepiller <[email-masked]> a écrit :
>Le 14 mai 2020 10:01:51 GMT-04:00, Julien Lepiller <[email-masked]>
>a écrit :
>>Le 14 mai 2020 09:48:46 GMT-04:00, Tobias Geerinckx-Rice via
>>Guix-patches via <[email-masked]> a écrit :
>>>* etc/gnu-store.mount.in: New file.
>>>* nix/local.mk (nodist_systemdservice_DATA): Add it.
>>>(etc/%.mount): New rule.
>>>* etc/guix-install.sh (sys_enable_guix_daemon): Install it.
>>>* doc/guix.texi (Binary Installation): Document it.
>>>---
>>>
>>>For
>>><https://lists.gnu.org/archive/html/help-guix/2020-05/msg00097.html>.
>>>
>>> doc/guix.texi          |  5 +++--
>>> etc/gnu-store.mount.in | 14 ++++++++++++++
>>> etc/guix-install.sh    | 12 +++++++++---
>>> nix/local.mk           | 12 +++++++++++-
>>> 4 files changed, 37 insertions(+), 6 deletions(-)
>>> create mode 100644 etc/gnu-store.mount.in
>>>
>>>diff --git a/doc/guix.texi b/doc/guix.texi
>>>index d6fbd85fde..5d80a7e405 100644
>>>--- a/doc/guix.texi
>>>+++ b/doc/guix.texi
>>>@@ -659,9 +659,10 @@ with these commands:
>>> @c
>>https://lists.gnu.org/archive/html/guix-devel/2017-01/msg01199.html
>>> 
>>> @example
>>>-# cp
>>~root/.config/guix/current/lib/systemd/system/guix-daemon.service
>>>\
>>>+# cp ~root/.config/guix/current/lib/systemd/system/gnu-store.mount \
>>>+    
>>~root/.config/guix/current/lib/systemd/system/guix-daemon.service
>>>\
>>>      /etc/systemd/system/
>>>-# systemctl enable --now guix-daemon
>>>+# systemctl enable --now gnu-store.mount guix-daemon
>>> @end example
>>> 
>>> If your host distro uses the Upstart init system:
>>>diff --git a/etc/gnu-store.mount.in b/etc/gnu-store.mount.in
>>>new file mode 100644
>>>index 0000000000..c94f2db72b
>>>--- /dev/null
>>>+++ b/etc/gnu-store.mount.in
>>>@@ -0,0 +1,14 @@
>>>+[Unit]
>>>+Description=Read-only @storedir@ for GNU Guix
>>>+DefaultDependencies=no
>>>+ConditionPathExists=@storedir@
>>>+Before=guix-daemon.service
>>>+
>>>+[Install]
>>>+WantedBy=guix-daemon.service
>>>+
>>>+[Mount]
>>>+What=@storedir@
>>>+Where=@storedir@
>>>+Type=none
>>>+Options=bind,ro
>>>diff --git a/etc/guix-install.sh b/etc/guix-install.sh
>>>index 4909d3f162..d252c132fb 100755
>>>--- a/etc/guix-install.sh
>>>+++ b/etc/guix-install.sh
>>>@@ -342,7 +342,13 @@ sys_enable_guix_daemon()
>>>                 _msg "${PAS}enabled Guix daemon via upstart"
>>>             ;;
>>>         systemd)
>>>-            { cp
>>>"${ROOT_HOME}/.config/guix/current/lib/systemd/system/guix-daemon.service"
>>>\
>>>+            { # systemd .mount units must be named after the target
>>>directory.
>>>+              # Here we assume a hard-coded name of /gnu/store.
>>>+              cp
>>>"${ROOT_HOME}/.config/guix/current/lib/systemd/system/gnu-store.mount"
>>>\
>>>+                 /etc/systemd/system/;
>>>+              chmod 664 /etc/systemd/system/gnu-store.mount;
>>>+
>>>+              cp
>>>"${ROOT_HOME}/.config/guix/current/lib/systemd/system/guix-daemon.service"
>>>\
>>>                  /etc/systemd/system/;
>>>               chmod 664 /etc/systemd/system/guix-daemon.service;
>>> 
>>>@@ -357,8 +363,8 @@ sys_enable_guix_daemon()
>>> 	      fi;
>>> 
>>>               systemctl daemon-reload &&
>>>-                  systemctl start guix-daemon &&
>>>-                  systemctl enable guix-daemon; } &&
>>>+                  systemctl start  gnu-store.mount guix-daemon &&
>>>+                  systemctl enable gnu-store.mount guix-daemon; } &&
>>>                 _msg "${PAS}enabled Guix daemon via systemd"
>>>             ;;
>>>         sysv-init)
>>>diff --git a/nix/local.mk b/nix/local.mk
>>>index a64bdd2137..435fdd389a 100644
>>>--- a/nix/local.mk
>>>+++ b/nix/local.mk
>>>@@ -155,7 +155,17 @@ noinst_HEADERS =						\
>>> 
>>> # The '.service' files for systemd.
>>> systemdservicedir = $(libdir)/systemd/system
>>>-nodist_systemdservice_DATA = etc/guix-daemon.service
>>>etc/guix-publish.service
>>>+nodist_systemdservice_DATA =			\
>>>+  etc/gnu-store.mount				\
>>>+  etc/guix-daemon.service			\
>>>+  etc/guix-publish.service
>>>+
>>>+etc/%.mount: etc/%.mount.in	\
>>>+			 $(top_builddir)/config.status
>>>+	$(AM_V_GEN)$(MKDIR_P) "`dirname $@`";	\
>>>+	$(SED) -e 's|@''storedir''@|$(storedir)|' <	\
>>>+	       "$<" > "$@.tmp";		\
>>>+	mv "$@.tmp" "$@"
>>> 
>>> etc/guix-%.service: etc/guix-%.service.in	\
>>> 			 $(top_builddir)/config.status
>>
>>I see that's how it's done with the existing service, but why sed the
>>.in file when we could let configure.ac take care of it?
>>
>>I'll try that on a VM of a foreign distro soonish and report. Thanks!
>
>I tested it on a debian VM and it worked well. I tested the installer
>script and it fails at installing the .mount unit, because it does not
>exist in the tarball.
>
>After installing the unit manually, I could start the .mount service
>and found that I was not able to remove store store items with rm. I
>checked that Guix is able to install new store items.

For non systemd distros, adding the following line to /etc/fstab works:

@storedir@ @storedir@ none defaults,bind,ro 0 0

Then running "mount -a" remounts the store read-only.

I'm not sure how to integrate this properly in the installer script.