cpio文件的压缩与解压缩
cpio解压方法：
1. # gunzip XXX.cpio.gz
2. cpio -idmv < XXX.cpio
制作cpio格式文件系统的方法：
1. 执行gen_initramfs_list.sh脚本：
# gen_initramfs_list.sh ./Filesystem/ >filelist
其中Filesystem文件夹是由上一步解压出来的cpio文件系统目录
2. 执行gen_init_cpio产生cpio文件：
# gen_init_cpio filelist >rootfs.cpio
３. 压缩cpio生成cpio.gz文件：
# gzip rootfs.cpio
所使用文件说明：
gen_initramfs_list.sh：用于产生filelist
gen_init_cpio.c ：工具gen_init_cpio的源码，编译后可以用
gen_init_cpio：用于产生cpio格式文件系统的可执行文件
gen_initramfs_list.sh的源码：
#!/bin/sh
# Copyright (C) Martin Schlemmer <azarah@nosferatu.za.org>
# Copyright (C) 2006 Sam Ravnborg <sam@ravnborg.org>
#
# Released under the terms of the GNU GPL
#
# Generate a cpio packed initramfs. It uses gen_init_cpio to generate
# the cpio archive, and then compresses it.
# The script may also be used to generate the inputfile used for gen_init_cpio
# This script assumes that gen_init_cpio is located in usr/ directory# error out on errors
set -eusage() {
cat << EOF
Usage:
$0 [-o <file>] [-u <uid>] [-g <gid>] {-d | <cpio_source>} ...-o <file> Create compressed initramfs file named <file> usinggen_init_cpio and compressor depending on the extension-u <uid> User ID to map to user ID 0 (root).<uid> is only meaningful if <cpio_source> is adirectory. "squash" forces all files to uid 0.-g <gid> Group ID to map to group ID 0 (root).<gid> is only meaningful if <cpio_source> is adirectory. "squash" forces all files to gid 0.<cpio_source> File list or directory for cpio archive.If <cpio_source> is a .cpio file it will be usedas direct input to initramfs.-d Output the default cpio list.All options except -o and -l may be repeated and are interpreted
sequentially and immediately. -u and -g states are preserved across
<cpio_source> options so an explicit "-u 0 -g 0" is required
to reset the root/group mapping.
EOF
}# awk style field access
# $1 - field number; rest is argument string
field() {shift $1 ; echo $1
}list_default_initramfs() {# echo usr/kinit/kinit:
}default_initramfs() {cat <<-EOF >> ${output}# This is a very simple, default initramfsdir /dev 0755 0 0nod /dev/console 0600 0 0 c 5 1dir /root 0700 0 0# file /kinit usr/kinit/kinit 0755 0 0# slink /init kinit 0755 0 0EOF
}filetype() {local argv1="$1"# symlink test must come before file testif [ -L "${argv1}" ]; thenecho "slink"elif [ -f "${argv1}" ]; thenecho "file"elif [ -d "${argv1}" ]; thenecho "dir"elif [ -b "${argv1}" -o -c "${argv1}" ]; thenecho "nod"elif [ -p "${argv1}" ]; thenecho "pipe"elif [ -S "${argv1}" ]; thenecho "sock"elseecho "invalid"fireturn 0
}list_print_mtime() {:
}print_mtime() {local my_mtime="0"if [ -e "$1" ]; thenmy_mtime=$(find "$1" -printf "%T@\n" | sort -r | head -n 1)fiecho "# Last modified: ${my_mtime}" >> ${output}echo "" >> ${output}
}list_parse() {[ ! -L "$1" ] && echo "$1 \\" || :
}# for each file print a line in following format
# <filetype> <name> <path to file> <octal mode> <uid> <gid>
# for links, devices etc the format differs. See gen_init_cpio for details
parse() {local location="$1"local name="/${location#${srcdir}}"# change '//' into '/'name=$(echo "$name" | sed -e 's://*:/:g')local mode="$2"local uid="$3"local gid="$4"local ftype=$(filetype "${location}")# remap uid/gid to 0 if necessary[ "$root_uid" = "squash" ] && uid=0 || [ "$uid" -eq "$root_uid" ] && uid=0[ "$root_gid" = "squash" ] && gid=0 || [ "$gid" -eq "$root_gid" ] && gid=0local str="${mode} ${uid} ${gid}"[ "${ftype}" = "invalid" ] && return 0[ "${location}" = "${srcdir}" ] && return 0case "${ftype}" in"file")str="${ftype} ${name} ${location} ${str}";;"nod")local dev=`LC_ALL=C ls -l "${location}"`local maj=`field 5 ${dev}`local min=`field 6 ${dev}`maj=${maj%,}[ -b "${location}" ] && dev="b" || dev="c"str="${ftype} ${name} ${str} ${dev} ${maj} ${min}";;"slink")local target=`readlink "${location}"`str="${ftype} ${name} ${target} ${str}";;*)str="${ftype} ${name} ${str}";;esacecho "${str}" >> ${output}return 0
}unknown_option() {printf "ERROR: unknown option \"$arg\"\n" >&2printf "If the filename validly begins with '-', " >&2printf "then it must be prefixed\n" >&2printf "by './' so that it won't be interpreted as an option." >&2printf "\n" >&2usage >&2exit 1
}list_header() {:
}header() {printf "\n#####################\n# $1\n" >> ${output}
}# process one directory (incl sub-directories)
dir_filelist() {${dep_list}header "$1"srcdir=$(echo "$1" | sed -e 's://*:/:g')dirlist=$(find "${srcdir}" -printf "%p %m %U %G\n")# If $dirlist is only one line, then the directory is emptyif [ "$(echo "${dirlist}" | wc -l)" -gt 1 ]; then${dep_list}print_mtime "$1"echo "${dirlist}" | \while read x; do${dep_list}parse ${x}donefi
}# if only one file is specified and it is .cpio file then use it direct as fs
# if a directory is specified then add all files in given direcotry to fs
# if a regular file is specified assume it is in gen_initramfs format
input_file() {source="$1"if [ -f "$1" ]; then${dep_list}header "$1"is_cpio="$(echo "$1" | sed 's/^.*\.cpio\(\..*\)\?/cpio/')"if [ $2 -eq 0 -a ${is_cpio} = "cpio" ]; thencpio_file=$1echo "$1" | grep -q '^.*\.cpio\..*' && is_cpio_compressed="compressed"[ ! -z ${dep_list} ] && echo "$1"return 0fiif [ -z ${dep_list} ]; thenprint_mtime "$1" >> ${output}cat "$1" >> ${output}elseecho "$1 \\"cat "$1" | while read type dir file perm ; doif [ "$type" = "file" ]; thenecho "$file \\";fidonefielif [ -d "$1" ]; thendir_filelist "$1"elseecho " ${prog}: Cannot open '$1'" >&2exit 1fi
}prog=$0
root_uid=0
root_gid=0
dep_list=
cpio_file=
cpio_list=
output="/dev/stdout"
output_file=""
is_cpio_compressed=
compr="gzip -n -9 -f"arg="$1"
case "$arg" in"-l") # files included in initramfs - used by kbuilddep_list="list_"echo "deps_initramfs := $0 \\"shift;;"-o") # generate compressed cpio image named $1shiftoutput_file="$1"cpio_list="$(mktemp ${TMPDIR:-/tmp}/cpiolist.XXXXXX)"output=${cpio_list}echo "$output_file" | grep -q "\.gz$" && compr="gzip -n -9 -f"echo "$output_file" | grep -q "\.bz2$" && compr="bzip2 -9 -f"echo "$output_file" | grep -q "\.lzma$" && compr="lzma -9 -f"echo "$output_file" | grep -q "\.xz$" && \compr="xz --check=crc32 --lzma2=dict=1MiB"echo "$output_file" | grep -q "\.lzo$" && compr="lzop -9 -f"echo "$output_file" | grep -q "\.cpio$" && compr="cat"shift;;
esac
while [ $# -gt 0 ]; doarg="$1"shiftcase "$arg" in"-u") # map $1 to uid=0 (root)root_uid="$1"shift;;"-g") # map $1 to gid=0 (root)root_gid="$1"shift;;"-d") # display default initramfs listdefault_list="$arg"${dep_list}default_initramfs;;"-h")usageexit 0;;*)case "$arg" in"-"*)unknown_option;;*) # input file/dir - process itinput_file "$arg" "$#";;esac;;esac
done# If output_file is set we will generate cpio archive and compress it
# we are careful to delete tmp files
if [ ! -z ${output_file} ]; thenif [ -z ${cpio_file} ]; thentimestamp=if test -n "$KBUILD_BUILD_TIMESTAMP"; thentimestamp="$(date -d"$KBUILD_BUILD_TIMESTAMP" +%s || :)"if test -n "$timestamp"; thentimestamp="-t $timestamp"fificpio_tfile="$(mktemp ${TMPDIR:-/tmp}/cpiofile.XXXXXX)"usr/gen_init_cpio $timestamp ${cpio_list} > ${cpio_tfile}elsecpio_tfile=${cpio_file}firm ${cpio_list}if [ "${is_cpio_compressed}" = "compressed" ]; thencat ${cpio_tfile} > ${output_file}else(cat ${cpio_tfile} | ${compr} - > ${output_file}) \|| (rm -f ${output_file} ; false)fi[ -z ${cpio_file} ] && rm ${cpio_tfile}
fi
exit 0
gen_init_cpio.c的源码：
#include <stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <string.h>
#include <unistd.h>
#include <time.h>
#include <fcntl.h>
#include <errno.h>
#include <ctype.h>
#include <limits.h>/** Original work by Jeff Garzik** External file lists, symlink, pipe and fifo support by Thayne Harbaugh* Hard link support by Luciano Rocha*/#define xstr(s) #s
#define str(s) xstr(s)static unsigned int offset;
static unsigned int ino = 721;
static time_t default_mtime;struct file_handler {const char *type;int (*handler)(const char *line);
};static void push_string(const char *name)
{unsigned int name_len = strlen(name) + 1;fputs(name, stdout);putchar(0);offset += name_len;
}static void push_pad (void)
{while (offset & 3) {putchar(0);offset++;}
}static void push_rest(const char *name)
{unsigned int name_len = strlen(name) + 1;unsigned int tmp_ofs;fputs(name, stdout);putchar(0);offset += name_len;tmp_ofs = name_len + 110;while (tmp_ofs & 3) {putchar(0);offset++;tmp_ofs++;}
}static void push_hdr(const char *s)
{fputs(s, stdout);offset += 110;
}static void cpio_trailer(void)
{char s[256];const char name[] = "TRAILER!!!";sprintf(s, "%s%08X%08X%08lX%08lX%08X%08lX""%08X%08X%08X%08X%08X%08X%08X","070701", /* magic */0, /* ino */0, /* mode */(long) 0, /* uid */(long) 0, /* gid */1, /* nlink */(long) 0, /* mtime */0, /* filesize */0, /* major */0, /* minor */0, /* rmajor */0, /* rminor */(unsigned)strlen(name)+1, /* namesize */0); /* chksum */push_hdr(s);push_rest(name);while (offset % 512) {putchar(0);offset++;}
}static int cpio_mkslink(const char *name, const char *target,unsigned int mode, uid_t uid, gid_t gid)
{char s[256];if (name[0] == '/')name++;sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX""%08X%08X%08X%08X%08X%08X%08X","070701", /* magic */ino++, /* ino */S_IFLNK | mode, /* mode */(long) uid, /* uid */(long) gid, /* gid */1, /* nlink */(long) default_mtime, /* mtime */(unsigned)strlen(target)+1, /* filesize */3, /* major */1, /* minor */0, /* rmajor */0, /* rminor */(unsigned)strlen(name) + 1,/* namesize */0); /* chksum */push_hdr(s);push_string(name);push_pad();push_string(target);push_pad();return 0;
}static int cpio_mkslink_line(const char *line)
{char name[PATH_MAX + 1];char target[PATH_MAX + 1];unsigned int mode;int uid;int gid;int rc = -1;if (5 != sscanf(line, "%" str(PATH_MAX) "s %" str(PATH_MAX) "s %o %d %d", name, target, &mode, &uid, &gid)) {fprintf(stderr, "Unrecognized dir format '%s'", line);goto fail;}rc = cpio_mkslink(name, target, mode, uid, gid);fail:return rc;
}static int cpio_mkgeneric(const char *name, unsigned int mode,uid_t uid, gid_t gid)
{char s[256];if (name[0] == '/')name++;sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX""%08X%08X%08X%08X%08X%08X%08X","070701", /* magic */ino++, /* ino */mode, /* mode */(long) uid, /* uid */(long) gid, /* gid */2, /* nlink */(long) default_mtime, /* mtime */0, /* filesize */3, /* major */1, /* minor */0, /* rmajor */0, /* rminor */(unsigned)strlen(name) + 1,/* namesize */0); /* chksum */push_hdr(s);push_rest(name);return 0;
}enum generic_types {GT_DIR,GT_PIPE,GT_SOCK
};struct generic_type {const char *type;mode_t mode;
};static struct generic_type generic_type_table[] = {[GT_DIR] = {.type = "dir",.mode = S_IFDIR},[GT_PIPE] = {.type = "pipe",.mode = S_IFIFO},[GT_SOCK] = {.type = "sock",.mode = S_IFSOCK}
};static int cpio_mkgeneric_line(const char *line, enum generic_types gt)
{char name[PATH_MAX + 1];unsigned int mode;int uid;int gid;int rc = -1;if (4 != sscanf(line, "%" str(PATH_MAX) "s %o %d %d", name, &mode, &uid, &gid)) {fprintf(stderr, "Unrecognized %s format '%s'",line, generic_type_table[gt].type);goto fail;}mode |= generic_type_table[gt].mode;rc = cpio_mkgeneric(name, mode, uid, gid);fail:return rc;
}static int cpio_mkdir_line(const char *line)
{return cpio_mkgeneric_line(line, GT_DIR);
}static int cpio_mkpipe_line(const char *line)
{return cpio_mkgeneric_line(line, GT_PIPE);
}static int cpio_mksock_line(const char *line)
{return cpio_mkgeneric_line(line, GT_SOCK);
}static int cpio_mknod(const char *name, unsigned int mode,uid_t uid, gid_t gid, char dev_type,unsigned int maj, unsigned int min)
{char s[256];if (dev_type == 'b')mode |= S_IFBLK;elsemode |= S_IFCHR;if (name[0] == '/')name++;sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX""%08X%08X%08X%08X%08X%08X%08X","070701", /* magic */ino++, /* ino */mode, /* mode */(long) uid, /* uid */(long) gid, /* gid */1, /* nlink */(long) default_mtime, /* mtime */0, /* filesize */3, /* major */1, /* minor */maj, /* rmajor */min, /* rminor */(unsigned)strlen(name) + 1,/* namesize */0); /* chksum */push_hdr(s);push_rest(name);return 0;
}static int cpio_mknod_line(const char *line)
{char name[PATH_MAX + 1];unsigned int mode;int uid;int gid;char dev_type;unsigned int maj;unsigned int min;int rc = -1;if (7 != sscanf(line, "%" str(PATH_MAX) "s %o %d %d %c %u %u",name, &mode, &uid, &gid, &dev_type, &maj, &min)) {fprintf(stderr, "Unrecognized nod format '%s'", line);goto fail;}rc = cpio_mknod(name, mode, uid, gid, dev_type, maj, min);fail:return rc;
}static int cpio_mkfile(const char *name, const char *location,unsigned int mode, uid_t uid, gid_t gid,unsigned int nlinks)
{char s[256];char *filebuf = NULL;struct stat buf;long size;int file = -1;int retval;int rc = -1;int namesize;int i;mode |= S_IFREG;file = open (location, O_RDONLY);if (file < 0) {fprintf (stderr, "File %s could not be opened for reading\n", location);goto error;}retval = fstat(file, &buf);if (retval) {fprintf(stderr, "File %s could not be stat()'ed\n", location);goto error;}filebuf = malloc(buf.st_size);if (!filebuf) {fprintf (stderr, "out of memory\n");goto error;}retval = read (file, filebuf, buf.st_size);if (retval < 0) {fprintf (stderr, "Can not read %s file\n", location);goto error;}size = 0;for (i = 1; i <= nlinks; i++) {/* data goes on last link */if (i == nlinks) size = buf.st_size;if (name[0] == '/')name++;namesize = strlen(name) + 1;sprintf(s,"%s%08X%08X%08lX%08lX%08X%08lX""%08lX%08X%08X%08X%08X%08X%08X","070701", /* magic */ino, /* ino */mode, /* mode */(long) uid, /* uid */(long) gid, /* gid */nlinks, /* nlink */(long) buf.st_mtime, /* mtime */size, /* filesize */3, /* major */1, /* minor */0, /* rmajor */0, /* rminor */namesize, /* namesize */0); /* chksum */push_hdr(s);push_string(name);push_pad();if (size) {if (fwrite(filebuf, size, 1, stdout) != 1) {fprintf(stderr, "writing filebuf failed\n");goto error;}offset += size;push_pad();}name += namesize;}ino++;rc = 0;error:if (filebuf) free(filebuf);if (file >= 0) close(file);return rc;
}static char *cpio_replace_env(char *new_location)
{char expanded[PATH_MAX + 1];char env_var[PATH_MAX + 1];char *start;char *end;for (start = NULL; (start = strstr(new_location, "${")); ) {end = strchr(start, '}');if (start < end) {*env_var = *expanded = '\0';strncat(env_var, start + 2, end - start - 2);strncat(expanded, new_location, start - new_location);strncat(expanded, getenv(env_var), PATH_MAX);strncat(expanded, end + 1, PATH_MAX);strncpy(new_location, expanded, PATH_MAX);} elsebreak;}return new_location;
}static int cpio_mkfile_line(const char *line)
{char name[PATH_MAX + 1];char *dname = NULL; /* malloc'ed buffer for hard links */char location[PATH_MAX + 1];unsigned int mode;int uid;int gid;int nlinks = 1;int end = 0, dname_len = 0;int rc = -1;if (5 > sscanf(line, "%" str(PATH_MAX) "s %" str(PATH_MAX)"s %o %d %d %n",name, location, &mode, &uid, &gid, &end)) {fprintf(stderr, "Unrecognized file format '%s'", line);goto fail;}if (end && isgraph(line[end])) {int len;int nend;dname = malloc(strlen(line));if (!dname) {fprintf (stderr, "out of memory (%d)\n", dname_len);goto fail;}dname_len = strlen(name) + 1;memcpy(dname, name, dname_len);do {nend = 0;if (sscanf(line + end, "%" str(PATH_MAX) "s %n",name, &nend) < 1)break;len = strlen(name) + 1;memcpy(dname + dname_len, name, len);dname_len += len;nlinks++;end += nend;} while (isgraph(line[end]));} else {dname = name;}rc = cpio_mkfile(dname, cpio_replace_env(location),mode, uid, gid, nlinks);fail:if (dname_len) free(dname);return rc;
}static void usage(const char *prog)
{fprintf(stderr, "Usage:\n""\t%s [-t <timestamp>] <cpio_list>\n""\n""<cpio_list> is a file containing newline separated entries that\n""describe the files to be included in the initramfs archive:\n""\n""# a comment\n""file <name> <location> <mode> <uid> <gid> [<hard links>]\n""dir <name> <mode> <uid> <gid>\n""nod <name> <mode> <uid> <gid> <dev_type> <maj> <min>\n""slink <name> <target> <mode> <uid> <gid>\n""pipe <name> <mode> <uid> <gid>\n""sock <name> <mode> <uid> <gid>\n""\n""<name> name of the file/dir/nod/etc in the archive\n""<location> location of the file in the current filesystem\n"" expands shell variables quoted with ${}\n""<target> link target\n""<mode> mode/permissions of the file\n""<uid> user id (0=root)\n""<gid> group id (0=root)\n""<dev_type> device type (b=block, c=character)\n""<maj> major number of nod\n""<min> minor number of nod\n""<hard links> space separated list of other links to file\n""\n""example:\n""# A simple initramfs\n""dir /dev 0755 0 0\n""nod /dev/console 0600 0 0 c 5 1\n""dir /root 0700 0 0\n""dir /sbin 0755 0 0\n""file /sbin/kinit /usr/src/klibc/kinit/kinit 0755 0 0\n""\n""<timestamp> is time in seconds since Epoch that will be used\n""as mtime for symlinks, special files and directories. The default\n""is to use the current time for these entries.\n",prog);
}struct file_handler file_handler_table[] = {{.type = "file",.handler = cpio_mkfile_line,}, {.type = "nod",.handler = cpio_mknod_line,}, {.type = "dir",.handler = cpio_mkdir_line,}, {.type = "slink",.handler = cpio_mkslink_line,}, {.type = "pipe",.handler = cpio_mkpipe_line,}, {.type = "sock",.handler = cpio_mksock_line,}, {.type = NULL,.handler = NULL,}
};#define LINE_SIZE (2 * PATH_MAX + 50)int main (int argc, char *argv[])
{FILE *cpio_list;char line[LINE_SIZE];char *args, *type;int ec = 0;int line_nr = 0;const char *filename;default_mtime = time(NULL);while (1) {int opt = getopt(argc, argv, "t:h");char *invalid;if (opt == -1)break;switch (opt) {case 't':default_mtime = strtol(optarg, &invalid, 10);if (!*optarg || *invalid) {fprintf(stderr, "Invalid timestamp: %s\n",optarg);usage(argv[0]);exit(1);}break;case 'h':case '?':usage(argv[0]);exit(opt == 'h' ? 0 : 1);}}if (argc - optind != 1) {usage(argv[0]);exit(1);}filename = argv[optind];if (!strcmp(filename, "-"))cpio_list = stdin;else if (!(cpio_list = fopen(filename, "r"))) {fprintf(stderr, "ERROR: unable to open '%s': %s\n\n",filename, strerror(errno));usage(argv[0]);exit(1);}while (fgets(line, LINE_SIZE, cpio_list)) {int type_idx;size_t slen = strlen(line);line_nr++;if ('#' == *line) {/* comment - skip to next line */continue;}if (! (type = strtok(line, " \t"))) {fprintf(stderr,"ERROR: incorrect format, could not locate file type line %d: '%s'\n",line_nr, line);ec = -1;break;}if ('\n' == *type) {/* a blank line */continue;}if (slen == strlen(type)) {/* must be an empty line */continue;}if (! (args = strtok(NULL, "\n"))) {fprintf(stderr,"ERROR: incorrect format, newline required line %d: '%s'\n",line_nr, line);ec = -1;}for (type_idx = 0; file_handler_table[type_idx].type; type_idx++) {int rc;if (! strcmp(line, file_handler_table[type_idx].type)) {if ((rc = file_handler_table[type_idx].handler(args))) {ec = rc;fprintf(stderr, " line %d\n", line_nr);}break;}}if (NULL == file_handler_table[type_idx].type) {fprintf(stderr, "unknown file type line %d: '%s'\n",line_nr, line);}}if (ec == 0)cpio_trailer();exit(ec);
}