[bug#69090] [PATCH v2] gnu: services: Add resize-fs-service.

[Richard Sent <richard@freakingpenguin.com>]

From: Gabriel Wicki <gabriel@erlikon.ch>

* gnu/services/admin.scm (resize-fs-configuration): New configuration
type.
(resize-fs-script, resize-fs-shepherd-service): New procedures.
resize-fs-service-type): New variable.
* doc/guix.texi (Miscallaneous Services): Document it.

Change-Id: Ib80c1af99ff62b68a79d7c463a5173f530514227
---
Hi Guix!

This is a resubmission of V1 this patch. It looks like the email got
messed up a bit and QA missed it. If QA still misses it I might send
it out again as a separate issue and link back to here.

To be 100% clear, this is Gabriel Wicki's code, not mine! Credit goes
to them for the contribution.

Some feedback: resize-fs-configuration's device field shouldn't be a
hardcoded string. It should be as flexible as the file-system record,
i.e. allow for labels and UUIDs. This should be possible using
canonicalize-device-name in gnu build file-system. The service should
also be extendable.

Depending on how parted operates this might not be trivial. I'm not
familiar with the tool, but I'd hope it can operate on partition
device files just as well as a block device + partition #.

 doc/guix.texi          | 41 +++++++++++++++++++
 gnu/services/admin.scm | 89 +++++++++++++++++++++++++++++++++++++++++-
 2 files changed, 129 insertions(+), 1 deletion(-)

diff --git a/doc/guix.texi b/doc/guix.texi
index 8073e3f6d4..29fde6bad5 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -41090,6 +41090,47 @@ Miscellaneous Services
 
 @c End of auto-generated fail2ban documentation.
 
+@cindex resize-fs
+@subsubheading Resize Filesystem service
+
+This service type lets you resize a live file-system during boot, which
+can be convenient if you flashed Guix on an SD Card (e.g. for an
+embedded device) or uploaded the image to a VPS.  In both cases the
+medium the image will reside upon may be larger than the image you want
+to produce.
+For an embedded device booting from an SD card you may use something like:
+@lisp
+(service resize-fs-service-type
+  (resize-fs-configuration
+    (device "/dev/mmcblk0")
+    (partition 2)))
+@end lisp
+
+Be extra cautious to use the correct device, partiion and end value, for
+the service will circumvent parted's safety checks - wrong use could end
+in loss of data or the corruption of your operating system.
+
+@table @asis
+
+@item @code{parted} (default: @code{parted}) (type: file-like)
+The parted package to use.
+
+@item @code{e2fsprogs} (default: @code{e2fsprogs}) (type: file-like)
+The e2fsprogs package to use.
+
+@item @code{device} (default: @code{"/dev/sdZ"}) (type: string)
+The device containing the file-system that shall be resized.
+
+@item @code{partition} (default: @code{-1}) (type: number)
+The partition number of the file-system that shall be resized.
+
+@item @code{end} (default: @code{"100%"}) (type: string)
+The end position of the resized partition as understood by the parted
+utility (e.g. "100%", "500M" or "16GiB").
+
+@end table
+
+
 @node Setuid Programs
 @section Setuid Programs
 
diff --git a/gnu/services/admin.scm b/gnu/services/admin.scm
index 0b325fddb1..acd7cacd3e 100644
--- a/gnu/services/admin.scm
+++ b/gnu/services/admin.scm
@@ -23,8 +23,11 @@ (define-module (gnu services admin)
   #:use-module (gnu packages admin)
   #:use-module ((gnu packages base)
                 #:select (canonical-package findutils coreutils sed))
+  #:use-module (gnu packages bash)
   #:use-module (gnu packages certs)
+  #:use-module (gnu packages disk)
   #:use-module (gnu packages package-management)
+  #:use-module (gnu packages linux)
   #:use-module (gnu services)
   #:use-module (gnu services configuration)
   #:use-module (gnu services mcron)
@@ -93,7 +96,16 @@ (define-module (gnu services admin)
             unattended-upgrade-configuration-services-to-restart
             unattended-upgrade-configuration-system-expiration
             unattended-upgrade-configuration-maximum-duration
-            unattended-upgrade-configuration-log-file))
+            unattended-upgrade-configuration-log-file
+
+            resize-fs-configuration
+            resize-fs-configuration?
+            resize-fs-configuration-parted
+            resize-fs-configuration-e2fsprogs
+            resize-fs-configuration-device
+            resize-fs-configuration-partition
+            resize-fs-configuration-end
+            resize-fs-service-type))
 
 ;;; Commentary:
 ;;;
@@ -537,4 +549,79 @@ (define unattended-upgrade-service-type
     "Periodically upgrade the system from the current configuration.")
    (default-value (unattended-upgrade-configuration))))
 
+\f
+;;;
+;;; Resize filesystem.
+;;;
+
+(define-configuration/no-serialization resize-fs-configuration
+  (parted
+   (file-like parted)
+   "The parted package to use.")
+  (e2fsprogs
+   (file-like e2fsprogs)
+   "The e2fsprogs package providing the resize2fs utility.")
+  (device
+   (string "/dev/sdZ")
+   "The device containing the partition to be resized.")
+  (partition
+   (number -1)
+   "The partition number that is to be resized.")
+  (end
+   (string "100%")
+   "The end position of the resized partition as understood by the parted \
+utility (e.g. \"100%\", \"500M\" or \"16GiB\")."))
+
+(define (resize-fs-script config)
+  (match-record
+      config <resize-fs-configuration> (parted e2fsprogs device partition end)
+    (let ((parted-bin (file-append parted "/sbin/parted"))
+          (resize2fs  (file-append e2fsprogs "/sbin/resize2fs"))
+          (device+partition (string-append device "p" (number->string partition))))
+      (mixed-text-file "resize-fs.sh"
+                       "#!/bin/sh
+echoerr() { printf \"$*\\n\" >&2 ; }
+
+cmd() {
+    " parted-bin " " device " ---pretend-input-tty <<EOF && " resize2fs " " device+partition "
+resizepart
+" (number->string partition) "
+Yes
+" end "
+EOF
+}
+
+set -o errexit
+set -o pipefail
+
+if cmd; then
+  echoerr \"Resizing successful\"
+else
+  echoerr \"resize-script returned $?\"
+fi
+"))))
+
+(define (resize-fs-shepherd-service config)
+  "Return a list of <shepherd-service> for resize-fs-service for CONFIG."
+  (let ((resize-script (resize-fs-script config)))
+    (shepherd-service
+     (documentation "Resize a file-system.  Intended for Guix Systems that are \
+booted from a system image flashed onto a larger medium.")
+     (provision '(resize-fs))
+     (requirement '(user-processes))
+     (one-shot? #t)
+     (respawn? #f)
+     (start #~(make-forkexec-constructor
+               (list #$(file-append bash "/bin/sh") #$resize-script))))))
+
+(define resize-fs-service-type
+  (service-type
+   (name 'resize-fs)
+   (description "Resize a partition during boot.")
+   (extensions
+    (list
+     (service-extension shepherd-root-service-type
+                        (compose list resize-fs-shepherd-service))))
+   (default-value (resize-fs-configuration))))
+
 ;;; admin.scm ends here

base-commit: 3597c736588c45efde3c22d533ea8774c3fdd235
-- 
2.41.0