add --skip=chroot/mount and --skip=chroot/mount/dev, --skip=chroot/mount/proc, --skip=chroot/mount/sys

coverage.txt

@@ -266,6 +266,9 @@ Test: remove-start-stop-daemon-and-policy-rc-d-in-hook
 
 Test: skip-start-stop-daemon-policy-rc
 
+Test: skip-mount
+Modes: unshare
+
 Test: compare-output-with-pre-seeded-var-cache-apt-archives
 Needs-QEMU: true
 Variants: any

mmdebstrap

@@ -1104,8 +1104,10 @@ sub run_chroot {
                     }
                 } elsif ($type == 3 or $type == 4) {
                     # character/block special
-                    if ((any { $_ eq $options->{mode} } ('root', 'unshare'))
-                        && !$options->{canmount}) {
+                    if (any { $_ =~ '^chroot/mount(?:/dev)?$' }
+                        @{ $options->{skip} }) {
+                        info "skipping chroot/mount/dev as requested";
+                    } elsif (!$options->{canmount}) {
                         warning "skipping bind-mounting ./dev/$fname";
                     } elsif (!$options->{havemknod}) {
                         if (!-d "$options->{root}/dev") {
@@ -1160,15 +1162,19 @@ sub run_chroot {
                             "$options->{root}/dev/$fname")
                           or error "mount ./dev/$fname failed: $?";
                     }
-                } elsif ($type == 5
-                    && (any { $_ eq $options->{mode} } ('root', 'unshare'))
-                    && !$options->{canmount}) {
+                } elsif ($type == 5) {
+                    # directory
+                    if (any { $_ =~ '^chroot/mount(?:/dev)?$' }
+                        @{ $options->{skip} }) {
+                        info "skipping chroot/mount/dev as requested";
+                    } elsif (!$options->{canmount}) {
                         warning "skipping bind-mounting ./dev/$fname";
-                } elsif ($type == 5) {    # directory
+                    } else {
                         if (!-d "$options->{root}/dev") {
                             warning(
                                 "skipping creation of ./dev/$fname because the"
-                              . " /dev directory is missing in the target");
+                                  . " /dev directory is missing in the target"
+                            );
                             next;
                         }
                         if (!-e "/dev/$fname" && $fname ne "pts/") {
@@ -1192,7 +1198,8 @@ sub run_chroot {
                             };
                             if (-e "$options->{root}/dev/$fname") {
                                 if (!-d "$options->{root}/dev/$fname") {
-                                error "./dev/$fname already exists but is not"
+                                    error
+                                      "./dev/$fname already exists but is not"
                                       . " a directory";
                                 }
                             } else {
@@ -1209,8 +1216,8 @@ sub run_chroot {
                                             } @$err
                                         ));
                                 } elsif ($num_created == 0) {
-                                error
-                                  "cannot create $options->{root}/dev/$fname";
+                                    error(  "cannot create $options->{root}"
+                                          . "/dev/$fname");
                                 }
                             }
                             chmod $mode, "$options->{root}/dev/$fname"
@@ -1251,6 +1258,7 @@ sub run_chroot {
                                 "$options->{root}/dev/$fname")
                               or error "mount ./dev/$fname failed: $?";
                         }
+                    }
                 } else {
                     error "unsupported type: $type";
                 }
@@ -1269,6 +1277,9 @@ sub run_chroot {
         # set because if we mount it before, then base-files will not be able
         # to extract those
         if ((any { $_ eq $options->{mode} } ('root', 'unshare'))
+            && (any { $_ =~ '^chroot/mount(?:/sys)?$' } @{ $options->{skip} })) {
+            info "skipping chroot/mount/sys as requested";
+        } elsif ((any { $_ eq $options->{mode} } ('root', 'unshare'))
             && !$options->{canmount}) {
             warning "skipping mount sysfs";
         } elsif ((any { $_ eq $options->{mode} } ('root', 'unshare'))
@@ -1344,6 +1355,9 @@ sub run_chroot {
             error "unknown mode: $options->{mode}";
         }
         if ((any { $_ eq $options->{mode} } ('root', 'unshare'))
+            && (any { $_ =~ '^chroot/mount(?:/proc)?$' } @{ $options->{skip} })) {
+            info "skipping chroot/mount/proc as requested";
+        } elsif ((any { $_ eq $options->{mode} } ('root', 'unshare'))
             && !$options->{canmount}) {
             warning "skipping mount proc";
         } elsif ((any { $_ eq $options->{mode} } ('root', 'unshare'))
@@ -6783,6 +6797,12 @@ out in B<extract> mode.
 Run B<--customize-hook> options and all F<customize*> scripts in B<--hook-dir>.
 This step is not carried out in B<extract> mode.
 
+Whenever B<mmdebstrap> does a chroot call in B<root> or B<unshare> modes, it
+will mount relevant device nodes, F</proc> and F</sys> into the chroot and
+unmount them afterwards. This can be disabled using B<--skip=chroot/mount> or
+specifically by B<--skip=chroot/mount/dev>, B<--skip=chroot/mount/proc> and
+B<--skip=chroot/mount/sys>, respectively.
+
 For each command that is run inside the chroot, B<mmdebstrap> will disable
 running services by temporarily moving F</usr/sbin/policy-rc.d> and
 F</sbin/start-stop-daemon> if they exist. This can be disabled with

tests/skip-mount

@@ -0,0 +1,12 @@
+#!/bin/sh
+set -eu
+export LC_ALL=C.UTF-8
+[ "{{ MODE }}" = "unshare" ]
+trap "rm -f /tmp/debian-chroot.tar" EXIT INT TERM
+{{ CMD }} --mode=unshare --variant=apt \
+	--skip=chroot/mount/proc,chroot/mount/sys \
+	--customize-hook='mountpoint "$1"/dev/null' \
+	--customize-hook='if mountpoint "$1"/sys; then exit 1; fi' \
+	--customize-hook='if mountpoint "$1"/proc; then exit 1; fi' \
+	{{ DIST }} /tmp/debian-chroot.tar {{ MIRROR }}
+tar -tf /tmp/debian-chroot.tar | sort | diff -u tar1.txt -