diff --git a/include/tpax/tpax.h b/include/tpax/tpax.h
index 332bc67..9e9fa38 100644
--- a/include/tpax/tpax.h
+++ b/include/tpax/tpax.h
@@ -147,6 +147,7 @@ tpax_api int  tpax_get_driver_fdctx     (const struct tpax_driver_ctx *, struct 
 tpax_api int  tpax_set_driver_fdctx     (struct tpax_driver_ctx *, const struct tpax_fd_ctx *);
 
 /* core api */
+tpax_api int  tpax_archive_append       (const struct tpax_driver_ctx *, const struct tpax_unit_ctx *);
 
 /* helper api */
 tpax_api int  tpax_path_copy            (char *, const char *, size_t, uint32_t, size_t *);
diff --git a/project/common.mk b/project/common.mk
index fcca006..378de0c 100644
--- a/project/common.mk
+++ b/project/common.mk
@@ -4,6 +4,7 @@ API_SRCS = \
 	src/driver/tpax_unit_ctx.c \
 	src/helper/tpax_path_copy.c \
 	src/helper/tpax_stat_compare.c \
+	src/logic/tpax_archive_append.c \
 	src/logic/tpax_init_ustar_header.c \
 	src/logic/tpax_file_create_memory_snapshot.c \
 	src/logic/tpax_file_create_tmpfs_snapshot.c \
diff --git a/src/logic/tpax_archive_append.c b/src/logic/tpax_archive_append.c
new file mode 100644
index 0000000..ce357b5
--- /dev/null
+++ b/src/logic/tpax_archive_append.c
@@ -0,0 +1,174 @@
+/******************************************************/
+/*  tpax: a topological pax implementation            */
+/*  Copyright (C) 2020  Z. Gilboa                     */
+/*  Released under GPLv2 and GPLv3; see COPYING.TPAX. */
+/******************************************************/
+
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <unistd.h>
+#include <fcntl.h>
+#include <errno.h>
+#include <grp.h>
+#include <pwd.h>
+#include <sys/stat.h>
+
+#include <tpax/tpax.h>
+#include <tpax/tpax_specs.h>
+#include "tpax_driver_impl.h"
+#include "tpax_tmpfile_impl.h"
+#include "tpax_errinfo_impl.h"
+
+#ifndef ssizeof
+#define ssizeof(x) (ssize_t)(sizeof(x))
+#endif
+
+static int tpax_archive_append_memory_data(
+	int                             fdout,
+	void *                          buf,
+	ssize_t                         nbytes)
+{
+	ssize_t ret;
+	char  * ch;
+
+	for (ch=buf; nbytes; ch+=ret) {
+		ret = write(fdout,ch,nbytes);
+
+		while ((ret < 0) && (errno == EINTR))
+			ret = write(fdout,ch,nbytes);
+
+		if (ret < 0)
+			return ret;
+
+		nbytes -= ret;
+	}
+
+	return 0;
+}
+
+static int tpax_archive_append_pad(
+	int                     fdout,
+	const struct stat *     st)
+{
+	ssize_t nbytes;
+	char    buf[512];
+
+	nbytes  = st->st_size;
+	nbytes += 0x1ff;
+	nbytes |= 0x1ff;
+	nbytes ^= 0x1ff;
+	nbytes -= st->st_size;
+
+	memset(buf,0,nbytes);
+
+	return tpax_archive_append_memory_data(
+		fdout,buf,nbytes);
+}
+
+int tpax_archive_append(
+	const struct tpax_driver_ctx *  dctx,
+	const struct tpax_unit_ctx *    uctx)
+{
+	struct tpax_ustar_header        uhdr;
+	int                             fdout;
+	int                             fdtmp;
+	ssize_t                         nread;
+	ssize_t                         nbytes;
+	void *                          buf;
+	size_t                          buflen;
+	size_t                          cmplen;
+	void *				membuf;
+	char                            sbuf[2048];
+
+	/* record errors */
+	tpax_driver_set_ectx(
+		dctx,0,
+		*uctx->path);
+
+	/* driver */
+	fdout = tpax_driver_fdout(dctx);
+
+	/* header */
+	if (tpax_init_ustar_header(
+			dctx,*uctx->path,uctx->st,
+			*uctx->link,&uhdr) < 0)
+		return TPAX_NESTED_ERROR(dctx);
+
+	/* buffer  */
+	membuf = 0;
+	fdtmp  = -1;
+
+	if ((buf = tpax_get_driver_anon_map_addr(dctx,&buflen)))
+		if (buflen >= (cmplen = uctx->st->st_size))
+			membuf = buf;
+
+	if (ssizeof(sbuf) >= (uctx->st->st_size))
+		membuf = sbuf;
+
+	/* snapshot */
+	if (membuf) {
+		if (tpax_file_create_memory_snapshot(
+				dctx,*uctx->path,
+				uctx->st,membuf) < 0)
+			return TPAX_NESTED_ERROR(dctx);
+	} else {
+		if ((fdtmp = tpax_file_create_tmpfs_snapshot(
+				dctx,*uctx->path,
+				uctx->st)) < 0)
+			return TPAX_NESTED_ERROR(dctx);
+
+		if (lseek(fdtmp,0,SEEK_SET) < 0)
+			return TPAX_SYSTEM_ERROR(dctx);
+	}
+
+	/* append header */
+	if (tpax_archive_append_memory_data(fdout,&uhdr,ssizeof(uhdr)) < 0) {
+		if (fdtmp >= 0)
+			close(fdtmp);
+
+		return TPAX_SYSTEM_ERROR(dctx);
+	}
+
+	/* append data from snapshot */
+	if (fdtmp >= 0) {
+		if (!buf) {
+			buf    = sbuf;
+			buflen = sizeof(sbuf);
+		}
+
+		for (nread=0; nread<uctx->st->st_size; ) {
+			nbytes = read(fdtmp,buf,buflen);
+
+			while ((nbytes < 0) && (errno == EINTR))
+				nbytes = read(fdtmp,buf,buflen);
+
+			if (nbytes < 0) {
+				close(fdtmp);
+				return TPAX_SYSTEM_ERROR(dctx);
+
+			} else if (nbytes == 0) {
+				close(fdtmp);
+				return TPAX_CUSTOM_ERROR(dctx,TPAX_ERR_FLOW_ERROR);
+
+			} else {
+				nread += nbytes;
+			}
+
+			if (tpax_archive_append_memory_data(fdout,buf,nbytes) < 0) {
+				close(fdtmp);
+				return TPAX_SYSTEM_ERROR(dctx);
+			}
+		}
+
+		close(fdtmp);
+	} else {
+		if (tpax_archive_append_memory_data(
+				fdout,membuf,
+				uctx->st->st_size) < 0)
+			return TPAX_SYSTEM_ERROR(dctx);
+	}
+
+	return tpax_archive_append_pad(
+		fdout,uctx->st);
+}