diff --git a/src/cmd/cli_dd.cpp b/src/cmd/cli_dd.cpp
index e43a494d..fd052d6f 100644
--- a/src/cmd/cli_dd.cpp
+++ b/src/cmd/cli_dd.cpp
@@ -37,7 +37,6 @@ struct dd_in_info_t
     // in
     std::string iimg, ifile;
     bool in_direct = false;
-    bool detect_size = true;
 
     // out
     cli_result_t result;
@@ -68,10 +67,7 @@ struct dd_in_info_t
                 return;
             }
             in_granularity = pool_it->second.bitmap_granularity;
-            if (detect_size)
-            {
-                in_size = iwatch->cfg.size;
-            }
+            in_size = iwatch->cfg.size;
             in_seekable = true;
             return;
         }
@@ -92,33 +88,31 @@ struct dd_in_info_t
         {
             ifd = 0;
         }
-        if (detect_size)
+        struct stat st;
+        if (fstat(ifd, &st) < 0)
         {
-            struct stat st;
-            if (fstat(ifd, &st) < 0)
+            result = (cli_result_t){ .err = errno, .text = "Failed to stat "+ifile+": "+std::string(strerror(errno)) };
+            close(ifd);
+            ifd = -1;
+            return;
+        }
+        if (S_ISREG(st.st_mode))
+        {
+            in_size = st.st_size;
+        }
+        else if (S_ISBLK(st.st_mode))
+        {
+            if (ioctl(ifd, BLKGETSIZE64, &in_size) < 0)
             {
-                result = (cli_result_t){ .err = errno, .text = "Failed to stat "+ifile+": "+std::string(strerror(errno)) };
+                result = (cli_result_t){ .err = errno, .text = "Failed to get "+ifile+" size: "+std::string(strerror(errno)) };
                 close(ifd);
                 ifd = -1;
                 return;
             }
-            if (S_ISREG(st.st_mode))
-            {
-                in_size = st.st_size;
-            }
-            else if (S_ISBLK(st.st_mode))
-            {
-                if (ioctl(ifd, BLKGETSIZE64, &in_size) < 0)
-                {
-                    result = (cli_result_t){ .err = errno, .text = "Failed to get "+ifile+" size: "+std::string(strerror(errno)) };
-                    close(ifd);
-                    ifd = -1;
-                    return;
-                }
-            }
         }
         in_seekable = false;
-        if (lseek(ifd, 1, SEEK_SET) == (off_t)1)
+        // a seekable character device has no size (st_size 0), read it like a pipe
+        if (!S_ISCHR(st.st_mode) && lseek(ifd, 1, SEEK_SET) == (off_t)1)
         {
             in_seekable = true;
             lseek(ifd, 0, SEEK_SET);
@@ -175,7 +169,7 @@ struct dd_out_info_t
         return NULL;
     }
 
-    bool open_output(cli_tool_t *parent, int & state, int base_state)
+    bool open_output(cli_tool_t *parent, int & state, int base_state, uint64_t oseek, uint64_t blocksize)
     {
         if (state == base_state)
             goto resume_1;
@@ -212,6 +206,13 @@ struct dd_out_info_t
                     return true;
                 }
             }
+            if ((oseek % out_granularity) || (blocksize % out_granularity))
+            {
+                result = (cli_result_t){ .err = EINVAL, .text = "Unaligned write to Vitastor is not supported" };
+                parent->cli->st_cli->close_watch(owatch);
+                owatch = NULL;
+                return true;
+            }
             if (out_size % 4096)
             {
                 out_size += (4096 - (out_size % 4096));
@@ -288,13 +289,13 @@ resume_2:
         }
         if (ofile != "")
         {
-            ofd = open(ofile.c_str(), (out_direct ? O_DIRECT : 0) | (out_append ? O_APPEND : O_RDWR) | (out_create ? O_CREAT : 0), 0666);
+            ofd = open(ofile.c_str(), (out_direct ? O_DIRECT : 0) | (out_append ? O_WRONLY|O_APPEND : O_RDWR) | (out_create ? O_CREAT : 0), 0666);
             if (ofd < 0)
             {
                 result = (cli_result_t){ .err = errno, .text = "Failed to open "+ofile+": "+std::string(strerror(errno)) };
                 return true;
             }
-            if (out_trunc && ftruncate(ofd, out_size) < 0)
+            if (out_trunc && ftruncate(ofd, out_size ? out_size : oseek) < 0)
             {
                 result = (cli_result_t){ .err = errno, .text = "Failed to truncate "+ofile+": "+std::string(strerror(errno)) };
                 return true;
@@ -314,6 +315,16 @@ resume_2:
             out_seekable = true;
             lseek(ofd, 0, SEEK_SET);
         }
+        struct stat st;
+        if (fstat(ofd, &st) < 0)
+        {
+            result = (cli_result_t){ .err = errno, .text = "Failed to stat "+(ofile != "" ? ofile : "stdout")+": "+std::string(strerror(errno)) };
+            return true;
+        }
+        if (!S_ISREG(st.st_mode) && !S_ISBLK(st.st_mode))
+        {
+            end_fsync = false;
+        }
         return true;
     }
 
@@ -395,6 +406,7 @@ struct cli_dd_t
     uint64_t written_size = 0;
     uint64_t written_progress = 0;
     timespec tv_begin = {}, tv_progress = {};
+    bool progress_shown = false;
     int state = 0;
     int copy_error = 0;
     int in_waiting = 0, out_waiting = 0;
@@ -413,6 +425,7 @@ struct cli_dd_t
             auto res = read(fd, buf, blocksize < to_skip ? blocksize : to_skip);
             if (res <= 0)
             {
+                free(buf);
                 return res == 0 ? -EPIPE : -errno;
             }
             to_skip -= res;
@@ -722,6 +735,12 @@ struct cli_dd_t
         {
             return;
         }
+        if (end && !end_status && !parent->json_output)
+        {
+            if (progress_shown)
+                fprintf(stderr, "\r\033[K");
+            return;
+        }
         timespec tv_now;
         clock_gettime(CLOCK_REALTIME, &tv_now);
         double sec_delta = ((tv_now.tv_sec - tv_progress.tv_sec) + (double)(tv_now.tv_nsec - tv_progress.tv_nsec)/1000000000.0);
@@ -764,6 +783,7 @@ struct cli_dd_t
                 format_size((uint64_t)(delta/sec_delta), true).c_str(),
                 format_size((uint64_t)(written_size/sec_total), true).c_str()
             );
+            progress_shown = true;
         }
     }
 
@@ -826,6 +846,12 @@ struct cli_dd_t
             state = 100;
             return;
         }
+        if (oinfo.ofile != "" && oinfo.out_append && oinfo.out_trunc)
+        {
+            result = (cli_result_t){ .err = EINVAL, .text = "conv=trunc and oflag=append can't be used together" };
+            state = 100;
+            return;
+        }
         if ((iinfo.iimg != "" ? "i"+iinfo.iimg : "f"+iinfo.ifile) == (oinfo.oimg != "" ? "i"+oinfo.oimg : "f"+oinfo.ofile))
         {
             result = (cli_result_t){ .err = EINVAL, .text = "Input and output image/file can't be equal" };
@@ -848,13 +874,20 @@ struct cli_dd_t
             state = 100;
             return;
         }
-        if (!oinfo.out_size)
+        if (iinfo.in_seekable && iseek >= iinfo.in_size)
+        {
+            iinfo.close_input(parent);
+            result = (cli_result_t){ .err = EINVAL, .text = "Input seek position is beyond end of input" };
+            state = 100;
+            return;
+        }
+        if (!oinfo.out_size && (iinfo.in_seekable || bytelimit))
         {
             oinfo.out_size = oseek + (iinfo.in_seekable && (!bytelimit || iinfo.in_size-iseek < bytelimit) ? iinfo.in_size-iseek : bytelimit);
         }
 resume_1:
 resume_2:
-        if (!oinfo.open_output(parent, state, 1))
+        if (!oinfo.open_output(parent, state, 1, oseek, blocksize))
         {
             return;
         }
@@ -865,17 +898,7 @@ resume_2:
             state = 100;
             return;
         }
-        if (oinfo.owatch && ((oseek % oinfo.out_granularity) || (blocksize % oinfo.out_granularity)))
-        {
-            result = (cli_result_t){ .err = EINVAL, .text = "Unaligned write to Vitastor is not supported" };
-            goto close_end;
-        }
         // Copy data
-        if (iinfo.in_seekable && iseek >= iinfo.in_size)
-        {
-            result = (cli_result_t){ .err = EINVAL, .text = "Input seek position is beyond end of input" };
-            goto close_end;
-        }
         if (!iinfo.iwatch && !iinfo.in_seekable && iseek)
         {
             // Read and ignore some data from input
@@ -889,9 +912,8 @@ resume_2:
         in_iodepth = iinfo.in_seekable ? iodepth : 1;
         out_iodepth = oinfo.out_seekable ? iodepth : 1;
         write_zero = write_zero || !oinfo.out_seekable;
-        oinfo.end_fsync = oinfo.end_fsync && oinfo.out_seekable;
         read_offset = 0;
-        read_end = iinfo.in_seekable ? iinfo.in_size-iseek : 0;
+        read_end = iinfo.in_seekable ? iinfo.in_size-iseek : UINT64_MAX;
         if (oinfo.out_size && (!read_end || read_end > oinfo.out_size-oseek))
             read_end = oinfo.out_size-oseek;
         if (bytelimit && (!read_end || read_end > bytelimit))
@@ -1000,10 +1022,14 @@ std::function<bool(cli_result_t &)> cli_tool_t::start_dd(json11::Json cfg)
     if (!dd->iodepth)
         dd->iodepth = 4;
     if (cfg["status"] == "none")
+    {
+        dd->end_status = false;
+        progress = false;
+    }
+    else if (cfg["status"] == "noxfer")
         dd->end_status = false;
     else if (cfg["status"] == "progress")
         progress = true;
-    dd->iinfo.detect_size = cfg["size"].is_null();
     dd->oinfo.out_size = parse_size(cfg["size"].as_string());
     dd->conv = explode_json(",", cfg["conv"]);
     dd->iflag = explode_json(",", cfg["iflag"]);
diff --git a/tests/test_dd.sh b/tests/test_dd.sh
index 36366e28..75ed2647 100755
--- a/tests/test_dd.sh
+++ b/tests/test_dd.sh
@@ -24,4 +24,85 @@ $VITASTOR_CLI dd iimg=testimg2 iodepth=4 bs=1M count=128 > ./testdata/testfile1
 diff ./testdata/testfile ./testdata/testfile1
 rm ./testdata/testfile1
 
+# size= sets the output size, the input size is still detected
+$VITASTOR_CLI dd iimg=testimg oimg=testimg3 iodepth=4 size=192M
+$VITASTOR_CLI dd if=./testdata/testfile oimg=testimg4 iodepth=4 size=192M
+for img in testimg3 testimg4; do
+    size=$($VITASTOR_CLI ls --json | jq -r '.[] | select(.name == "'$img'") | .size')
+    [[ "$size" = $((192*1024*1024)) ]] || format_error "dd size=192M created $img with size $size"
+    $VITASTOR_CLI dd iimg=$img iodepth=4 bs=1M count=128 > ./testdata/testfile1
+    diff ./testdata/testfile ./testdata/testfile1
+    rm ./testdata/testfile1
+done
+
+# skip beyond the end of input fails before the output image is created
+rc=0
+$VITASTOR_CLI dd iimg=testimg oimg=testimg5 bs=1M skip=200 count=1 || rc=$?
+[[ $rc = 22 ]] || format_error "dd skip beyond the end of input returned $rc instead of EINVAL"
+if $VITASTOR_CLI ls --json | jq -e '.[] | select(.name == "testimg5")'; then
+    format_error "dd skip beyond the end of input created the output image"
+fi
+
+# status=none prints nothing, also with the default --progress 1
+$VITASTOR_CLI dd iimg=testimg of=./testdata/testfile1 iodepth=4 status=none 2>./testdata/dd.err
+[[ ! -s ./testdata/dd.err ]] || format_error "dd status=none printed: $(cat ./testdata/dd.err)"
+diff ./testdata/testfile ./testdata/testfile1
+rm ./testdata/testfile1
+
+# status=noxfer drops the final statistics line
+$VITASTOR_CLI --progress 0 dd iimg=testimg of=./testdata/testfile1 iodepth=4 status=noxfer 2>./testdata/dd.err
+[[ ! -s ./testdata/dd.err ]] || format_error "dd status=noxfer printed: $(cat ./testdata/dd.err)"
+rm ./testdata/testfile1
+# with --progress 1 the progress line, if it was shown at all, is cleared at the end
+clear_line=$'\r\033[K'
+for count in 128 4; do
+    $VITASTOR_CLI dd iimg=testimg of=./testdata/testfile1 iodepth=4 bs=1M count=$count status=noxfer 2>./testdata/dd.err
+    if [[ $(wc -l < ./testdata/dd.err) != 0 || ( -s ./testdata/dd.err && "$(cat ./testdata/dd.err)" != *copied*"$clear_line" ) ]]; then
+        format_error "dd status=noxfer count=$count printed: $(cat -v ./testdata/dd.err)"
+    fi
+    head -c ${count}M ./testdata/testfile | cmp - ./testdata/testfile1
+    rm ./testdata/testfile1
+done
+
+# oflag=append appends to the output file
+cp ./testdata/over ./testdata/testfile1
+$VITASTOR_CLI dd iimg=testimg of=./testdata/testfile1 iodepth=4 bs=1M count=8 oflag=append
+(cat ./testdata/over; head -c 8M ./testdata/testfile) | cmp - ./testdata/testfile1 || format_error "dd oflag=append did not append to the output file"
+rm ./testdata/testfile1
+# conv=trunc contradicts oflag=append: fail without touching the output file
+cp ./testdata/over ./testdata/testfile1
+rc=0
+$VITASTOR_CLI dd iimg=testimg of=./testdata/testfile1 iodepth=4 bs=1M count=8 oflag=append conv=trunc || rc=$?
+[[ $rc = 22 ]] || format_error "dd conv=trunc oflag=append returned $rc instead of EINVAL"
+cmp ./testdata/over ./testdata/testfile1 || format_error "dd conv=trunc oflag=append changed the output file"
+rm ./testdata/testfile1
+
+# pipe in without count - copy to the end of input
+$VITASTOR_CLI dd iimg=testimg iodepth=4 | $VITASTOR_CLI dd of=./testdata/testfile1 iodepth=4
+diff ./testdata/testfile ./testdata/testfile1
+rm ./testdata/testfile1
+$VITASTOR_CLI dd iimg=testimg iodepth=4 | $VITASTOR_CLI dd of=./testdata/testfile1 iodepth=4 bs=1M seek=4
+(head -c 4M /dev/zero; cat ./testdata/testfile) | cmp - ./testdata/testfile1 || format_error "dd from a pipe with seek= did not copy the whole input"
+rm ./testdata/testfile1
+
+# unaligned image I/O fails with EINVAL before the output image is created or resized
+for args in "if=./testdata/testfile oimg=testimg6 seek=512B" "if=./testdata/testfile oimg=testimg2 seek=512B" "iimg=testimg oimg=testimg7 skip=512B"; do
+    rc=0
+    $VITASTOR_CLI dd iodepth=4 $args || rc=$?
+    [[ $rc = 22 ]] || format_error "dd $args returned $rc instead of EINVAL"
+done
+if $VITASTOR_CLI ls --json | jq -e '.[] | select(.name == "testimg6" or .name == "testimg7")'; then
+    format_error "dd with unaligned image I/O created the output image"
+fi
+size=$($VITASTOR_CLI ls --json | jq -r '.[] | select(.name == "testimg2") | .size')
+[[ "$size" = $((128*1024*1024)) ]] || format_error "dd with unaligned seek resized testimg2 to $size"
+
+# a character device is read like a pipe, up to count= or size=
+$VITASTOR_CLI dd if=/dev/zero oimg=testimg8 size=32M
+size=$($VITASTOR_CLI ls --json | jq -r '.[] | select(.name == "testimg8") | .size')
+[[ "$size" = $((32*1024*1024)) ]] || format_error "dd if=/dev/zero size=32M created testimg8 with size $size"
+$VITASTOR_CLI dd if=/dev/zero of=./testdata/testfile1 bs=1M count=4 conv=nosparse
+head -c 4M /dev/zero | cmp - ./testdata/testfile1 || format_error "dd if=/dev/zero count=4 did not write 4 MiB of zeros"
+rm ./testdata/testfile1
+
 format_green OK