Add remove image support

README.md

@@ -390,6 +390,16 @@ forge            latest                 10.17M  2021-05-27 00:32:08
 %
 ```
 
+To remove an image, give its name and tag (the tag defaults to `latest`):
+```
+% sudo cblock images --remove freebsd-13_4:latest
+Removed freebsd-13_4:latest
+%
+```
+If the image has other tags, only this tag is removed. The image itself is
+removed with its last tag, and cblockd refuses to remove an image that a
+running cellblock or build is using.
+
 ### Launching your Cellblock
 
 Now we are ready to launch the container. Note with `--host-networking` the cblock daemon

src/cblock/image.c

@@ -43,23 +43,28 @@
 struct image_config {
 	int		 i_quiet;
 	int		 i_do_prune;
+	int		 i_do_remove;
 };
 
 static struct option image_options[] = {
 	{ "help",		no_argument, 0, 'h' },
 	{ "quiet",		no_argument, 0, 'q' },
 	{ "prune",		no_argument, 0, 'p' },
+	{ "remove",		no_argument, 0, 'r' },
 	{ 0, 0, 0, 0 }
 };
 
 static void
 image_usage(void)
 {
 	(void) fprintf(stderr,
-	    "Usage: cblock images [OPTIONS]\n\n"
+	    "Usage: cblock images [OPTIONS]\n"
+	    "       cblock images --remove NAME[:TAG] ...\n\n"
 	    "Options\n"
 	    " -h, --help                  Print help\n"
 	    " -p, --prune                 Remove stopped/dead images\n"
+	    " -r, --remove                Remove image tags, and each image\n"
+	    "                             with its last tag unless it is in use\n"
 	    " -q, --quiet                 Do not print column headers\n");
 	exit(1);
 }
@@ -78,6 +83,37 @@ image_prune(struct image_config *icp __attribute__((unused)), int ctlsock)
 	sock_ipc_from_sock_to_tty(ctlsock);
 }
 
+static void
+image_remove(int argc, char *argv[], int ctlsock)
+{
+	struct cblock_generic_command arg;
+	char *marshalled;
+	vec_t *vec;
+	int k;
+
+	vec = vec_init(argc + 1);
+	if (vec == NULL) {
+		err(1, "vec_init failed");
+	}
+	for (k = 0; k < argc; k++) {
+		vec_append(vec, argv[k]);
+	}
+	vec_finalize(vec);
+	marshalled = vec_marshal(vec);
+	if (marshalled == NULL) {
+		err(1, "vec_marshal failed");
+	}
+	bzero(&arg, sizeof(arg));
+	snprintf(arg.p_cmdname, sizeof(arg.p_cmdname), "image_remove");
+	arg.p_mlen = vec->vec_marshalled_len;
+	if (sock_ipc_write_u32(ctlsock, PRISON_IPC_GENERIC_COMMAND) == -1 ||
+	    proto_send_generic_command(ctlsock, &arg, marshalled) == -1) {
+		errx(1, "failed to send image request");
+	}
+	vec_free(vec);
+	sock_ipc_from_sock_to_tty(ctlsock);
+}
+
 static void
 image_get(struct image_config *icp __attribute__((unused)), int ctlsock)
 {
@@ -102,7 +138,7 @@ image_main(int argc, char *argv [], int ctlsock)
 	reset_getopt_state();
 	while (1) {
 		option_index = 0;
-		c = getopt_long(argc, argv, "qhp", image_options,
+		c = getopt_long(argc, argv, "qhpr", image_options,
 		    &option_index);
 		if (c == -1) {
 			break;
@@ -111,6 +147,9 @@ image_main(int argc, char *argv [], int ctlsock)
 		case 'p':
 			ic.i_do_prune = 1;
 			break;
+		case 'r':
+			ic.i_do_remove = 1;
+			break;
 		case 'q':
 			ic.i_quiet = 1;
 			break;
@@ -124,6 +163,13 @@ image_main(int argc, char *argv [], int ctlsock)
 	}
 	argc -= optind;
 	argv += optind;
+	if (ic.i_do_remove) {
+		if (argc == 0) {
+			image_usage();
+		}
+		image_remove(argc, argv, ctlsock);
+		return (0);
+	}
 	if (ic.i_do_prune) {
 		image_prune(&ic, ctlsock);
 		return (0);

src/cblockd/exec.c

@@ -55,6 +55,7 @@ static struct command_ent command_list[] = {
 	{ "instance_prune",	"cmd_instance_prune.sh" },
 	{ "image_prune",	"cmd_image_prune.sh" },
 	{ "image_list",		"cmd_image.sh" },
+	{ "image_remove",	"cmd_image_remove.sh" },
 	{ NULL,			NULL }
 };
 
@@ -128,6 +129,11 @@ dispatch_generic_command(int sock)
 		vec_append(cmd_vec, script_path);
 		vec_append(cmd_vec, "-R");
 		vec_append(cmd_vec, gcfg.c_data_dir);
+		/*
+		 * The client's arguments follow "--" so the script can't
+		 * take any of them as an option, such as another -R.
+		 */
+		vec_append(cmd_vec, "--");
 		if (vec_merge(vec, cmd_vec) != 0) {
 			err(1, "error argv vectors: HINT: increase cmd_vec");
 		}

src/libcblock/vec.c

@@ -172,7 +172,8 @@ vec_merge(vec_t *from, vec_t *to)
 {
 	int k;
 
-	if ((from->vec_used + to->vec_used) > to->vec_alloc) {
+	/* Leave room for the NULL that vec_finalize() adds. */
+	if ((from->vec_used + to->vec_used) >= to->vec_alloc) {
 		fprintf(stderr, "vec_append: overflow\n");
 		return (VEC_OVERFLOW);
 	}

src/shell/Makefile

@@ -1,4 +1,5 @@
 TARGETS=cmd_image.sh \
+	cmd_image_remove.sh \
 	cmd_image_prune.sh \
 	cmd_instance_prune.sh \
 	common.sh \

src/shell/cmd_image_prune.sh

@@ -49,19 +49,7 @@ do_image_purge()
             continue
         fi
         printf "Removing un-referenced image: %s\n" $(basename $image)
-        case $CBLOCK_FS in
-        zfs)
-            vol=$(path_to_vol $image)
-            zfs destroy -r "$vol"
-            rm -fr "$vol"
-            ;;
-        ufs)
-            chflags -R noschg "$image"
-            rm -Wfr "$image"
-            ;;
-        *)
-            echo "No match on CBLOCK_FS"
-        esac
+        remove_image "$image"
     done
 }
 

src/shell/cmd_image_remove.sh

@@ -0,0 +1,94 @@
+#!/bin/sh
+#
+# Copyright (c) 2026 Christian S.J. Peron
+# All rights reserved.
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions
+# are met:
+# 1. Redistributions of source code must retain the above copyright
+#    notice, this list of conditions and the following disclaimer.
+# 2. Redistributions in binary form must reproduce the above copyright
+#    notice, this list of conditions and the following disclaimer in the
+#    documentation and/or other materials provided with the distribution.
+#
+# THIS SOFTWARE IS PROVIDED BY THE AUTHOR AND CONTRIBUTORS ``AS IS'' AND
+# ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR OR CONTRIBUTORS BE LIABLE
+# FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
+# DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
+# OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
+# HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
+# LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
+# OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+# SUCH DAMAGE.
+#
+# Remove image tags: cmd_image_remove.sh -R DATA_DIR -- NAME[:TAG] ...
+# A missing tag means "latest". The image itself is deleted with its
+# last tag, unless a running instance or build is using it.
+#
+. "$(dirname "$0")/common.sh"
+data_dir=""
+
+remove_tag()
+{
+    name="${1%%:*}"
+    tag="latest"
+    case "$1" in
+    *:*)
+        tag="${1#*:}"
+        ;;
+    esac
+    # The names come from the client. Keep them inside the images
+    # directory.
+    case "$name:$tag" in
+    -*|*/*|:*|*:|*:*:*)
+        echo "${1}: invalid image name"
+        return 1
+        ;;
+    esac
+    link="${data_dir}/images/${name}:${tag}"
+    if [ ! -h "$link" ]; then
+        echo "${name}:${tag}: no such image"
+        return 1
+    fi
+    image=$(readlink "$link")
+    for other in $(symlinks); do
+        if [ "$other" != "$link" ] && [ "$(readlink "$other")" = "$image" ]; then
+            rm "$link"
+            echo "Untagged ${name}:${tag}"
+            return 0
+        fi
+    done
+    if image_in_use "$image"; then
+        echo "${name}:${tag}: image is in use, not removed"
+        return 1
+    fi
+    rm "$link"
+    remove_image "$image" || return 1
+    echo "Removed ${name}:${tag}"
+}
+
+while getopts "R:" opt; do
+    case $opt in
+        R)
+            data_dir="$OPTARG"
+            ;;
+        *)
+            exit 1
+            ;;
+    esac
+done
+shift $((OPTIND - 1))
+
+if [ ! "$data_dir" ]; then
+    echo "Must specify cblock data directory -R"
+    exit 1
+fi
+
+status=0
+for arg in "$@"; do
+    remove_tag "$arg" || status=1
+done
+exit $status

src/shell/common.sh

@@ -42,6 +42,46 @@ symlinks()
       -mindepth 1 -maxdepth 1 -type l
 }
 
+# Delete an image directory (or dataset) under ${data_dir}/images. The
+# caller makes sure no tag points at it and nothing is using it.
+remove_image()
+{
+    case $CBLOCK_FS in
+    zfs)
+        zfs destroy -r "$(path_to_vol "$1")"
+        rm -fr "$1"
+        ;;
+    ufs)
+        chflags -R noschg "$1"
+        rm -fr "$1"
+        ;;
+    *)
+        echo "No match on CBLOCK_FS"
+        return 1
+        ;;
+    esac
+}
+
+# Succeeds if a running instance or build is using the image in $1.
+# Launches and builds mount the image's root as the lower layer of a
+# unionfs (ufs), or clone a snapshot of its dataset (zfs).
+image_in_use()
+{
+    case $CBLOCK_FS in
+    zfs)
+        zfs list -H -o clones -t snapshot -d 1 "$(path_to_vol "$1")" | \
+          grep -qv '^-$'
+        ;;
+    ufs)
+        mount -p | awk -v dir="$1/root" '
+            { n = split($1, layer, ":")
+              for (i = 1; i <= n; i++)
+                  if (layer[i] == dir) found = 1 }
+            END { exit !found }'
+        ;;
+    esac
+}
+
 ip_to_int()
 {
     echo "$1" | awk -F. '{ print (($1 * 256 + $2) * 256 + $3) * 256 + $4 }'