[gparted/systemd-masking: 4/5] Only mask Systemd mounts on block devices (#129)

[Curtis Gedak <gedakc src gnome org>]

commit 1a5614b3dddcb4830d5b6e86fd5c526a30c714a0
Author: Mike Fleetwood <mike fleetwood googlemail com>
Date:   Mon Jan 4 23:00:54 2021 +0000

    Only mask Systemd mounts on block devices (#129)
    
    The gparted shell wrapper masks Systemd mount units to prevent it
    automounting file systems while GParted is running [1], excluding
    virtual file system which GParted isn't interested in [2].  The problem
    is that there are a lot of virtual file systems and they have changed
    between Fedora 19 and 33 so now the exclusion list is out of date.
    
    Run GParted on Fedora 33 and query the mount units while it is running:
        $ systemctl list-units -t mount --full --all
          UNIT                          LOAD   ACTIVE   SUB     DESCRIPTION
          -.mount                       loaded active   mounted Root Mount
        * boot.mount                    masked active   mounted /boot
          dev-hugepages.mount           loaded active   mounted Huge Pages File System
          dev-mqueue.mount              loaded active   mounted POSIX Message Queue File System
        * home.mount                    masked active   mounted /home
        * proc-fs-nfsd.mount            masked inactive dead    proc-fs-nfsd.mount
          proc-sys-fs-binfmt_misc.mount loaded inactive dead    Arbitrary Executable File Formats File System
          run-user-1000-gvfs.mount      loaded active   mounted /run/user/1000/gvfs
        * run-user-1000.mount           masked active   mounted /run/user/1000
        * run-user-42.mount             masked active   mounted /run/user/42
          sys-fs-fuse-connections.mount loaded active   mounted FUSE Control File System
          sys-kernel-config.mount       loaded active   mounted Kernel Configuration File System
          sys-kernel-debug.mount        loaded active   mounted Kernel Debug File System
        * sys-kernel-tracing.mount      masked active   mounted /sys/kernel/tracing
        * sysroot.mount                 masked inactive dead    sysroot.mount
        * tmp.mount                     masked active   mounted /tmp
        * var-lib-machines.mount        masked inactive dead    var-lib-machines.mount
        * var-lib-nfs-rpc_pipefs.mount  masked active   mounted /var/lib/nfs/rpc_pipefs
        * var.mount                     masked inactive dead    var.mount
    
        LOAD   = Reflects whether the unit definition was properly loaded.
        ACTIVE = The high-level unit activation state, i.e. generalization of SUB.
        SUB    = The low-level unit activation state, values depend on unit type.
    
        19 loaded units listed.
        To show all installed unit files use 'systemctl list-unit-files'.
    
    So it masked these virtual file systems which didn't need to be masked:
        * proc-fs-nfsd.mount            masked inactive dead    proc-fs-nfsd.mount
        * run-user-1000.mount           masked active   mounted /run/user/1000
        * run-user-42.mount             masked active   mounted /run/user/42
        * sys-kernel-tracing.mount      masked active   mounted /sys/kernel/tracing
        * var-lib-machines.mount        masked inactive dead    var-lib-machines.mount
        * var-lib-nfs-rpc_pipefs.mount  masked active   mounted /var/lib/nfs/rpc_pipefs
    
    Lines from /proc/partitions for some of these virtual file systems:
        $  egrep '/run/user|/sys/kernel/tracing|/var/lib/nfs/rpc_pipefs' /proc/mounts
        tmpfs /run/user/42 tmpfs 
rw,seclabel,nosuid,nodev,relatime,size=202656k,nr_inodes=50664,mode=700,uid=42,gid=42,inode64 0 0
        tmpfs /run/user/1000 tmpfs 
rw,seclabel,nosuid,nodev,relatime,size=202656k,nr_inodes=50664,mode=700,uid=1000,gid=1000,inode64 0 0
        none /sys/kernel/tracing tracefs rw,seclabel,relatime 0 0
        sunrpc /var/lib/nfs/rpc_pipefs rpc_pipefs rw,relatime 0 0
        gvfsd-fuse /run/user/1000/gvfs fuse.gvfsd-fuse rw,nosuid,nodev,relatime,user_id=1000,group_id=1000 0 0
    
    And for contrast the lines from /proc/mounts for disk backed file systems:
        $ egrep '^/dev/' /proc/mounts
        /dev/sda1 /boot ext4 rw,seclabel,relatime 0 0
        /dev/sda2 / btrfs rw,seclabel,relatime,space_cache,subvolid=258,subvol=/root 0 0
        /dev/sda2 /home btrfs rw,seclabel,relatime,space_cache,subvolid=256,subvol=/home 0 0
    
    Going back to first principles GParted cares that Systemd doesn't
    automount file systems on block devices.  So instead only mask mount
    units which are on block devices.  Where the 'What' property starts
    "/dev/".
    
    Systemd maintains hundreds of properties for each unit.
        $ systemctl show boot.mount | wc -l
        221
    
    The properties of interest for all mount units can be queries like this:
        $ systemctl show --all --property=What,Id,LoadState '*.mount'
        ...
    
        What=sunrpc
        Id=var-lib-nfs-rpc_pipefs.mount
        LoadState=masked
    
        What=/dev/sda1
        Id=boot.mount
        LoadState=masked
    
        ...
    
    [1] 4c109df9b59e55699bd42023cf4007ee359793e9
        Use systemctl runtime mask to prevent automounting (#701676)
    
    [2] 43de8e326a9f6f099e5274619f16039bdc20c1a4
        Do not mask virtual file systems when using systemctl (#708378)
    
    Closes #129 - Unit \xe2\x97\x8f.service does not exist, proceeding
                  anyway

 gparted.in | 19 ++++++++++++++++---
 1 file changed, 16 insertions(+), 3 deletions(-)
---
diff --git a/gparted.in b/gparted.in
index 7fa8b363..4ddd7b90 100755
--- a/gparted.in
+++ b/gparted.in
@@ -144,9 +144,22 @@ done
 #  Use systemctl to prevent automount by masking currently unmasked mount points
 #
 if test "x$HAVE_SYSTEMCTL" = "xyes"; then
-       MOUNTLIST=`systemctl list-units --full --all -t mount --no-legend --plain \
-         | grep -v masked | cut -f1 -d' ' \
-         | egrep -v 
'^(dev-hugepages|dev-mqueue|proc-sys-fs-binfmt_misc|run-user-.*-gvfs|sys-fs-fuse-connections|sys-kernel-config|sys-kernel-debug)'`
+       MOUNTLIST=`systemctl show --all --property=What,Id,LoadState '*.mount' | \
+       awk '
+       function clear_properties() {
+               what = ""; id = ""; loadstate = ""
+       }
+       function process_unit() {
+               if (substr(what,1,5) == "/dev/" && loadstate != "masked")
+                       print id
+               clear_properties()
+       }
+       /^What=/      { what      = substr($0,6) }
+       /^Id=/        { id        = substr($0,4) }
+       /^LoadState=/ { loadstate = substr($0,11) }
+       /^$/          { process_unit() }
+       END           { process_unit() }
+       '`
        systemctl --runtime mask --quiet -- $MOUNTLIST
 fi