# OpenWrt sysupgrade 升级原理

OpenWrt的升级是使用sysupgrade工具来升级的，该工具为`/sbin/sysupgrade`脚本，可以附带很多参数，但是我们一般就直接使用命令`sysupgrade openwrt-ramips-mt7621-device-squashfs-sysupgrade.bin`升级

|参数	|说明         |
|-------|-------------|
|-i	    |开启交互模式|
|-d	    |重启前延迟，延迟秒数是传进来的|
|-v	    |会打印sysupgrade脚本中的一些信息，脚本中默认打印|
|-q	    |与-v相反|
|-n	    |升级后不保存配置，默认保存配置|
|-c	    |保存所有的改动配置文件到/etc/|
|-b	    |用sysupgrade.conf中指定的文件，创建.tar.gz格式备份文件|
|-r	    |用上步创建的.tar.gz文件，恢复配置|
|-l	    |列出将会备份的文件列表|
|-f	    |从.tar.gz恢复配置|
|-F	    |即使升级文件检测失败，也要升级，这个参数是危险的，慎用|
|-T	    |验证升级文件和.tar.gz配置文件，但不升级|
|-h	    |打印帮助信息|

## 脚本分析

sysupgrade的升级流程查看`/sbin/sysupgrade`脚本

1. check校验固件合法性
   sysupgrade的第一步就是校验固件合法性，如下判断platform_check_image函数存在则开始执行。

   ```bash
   type platform_check_image >/dev/null 2>/dev/null || {
   	echo "Firmware upgrade is not implemented for this platform."
   	exit 1
   }
   
   for check in $sysupgrade_image_check; do
           ( eval "$check \"\$1\"" ) || {             
                   echo "Image check '$check' $1 failed."
                   return 1
           }                         
   done   
   
   ```

   该函数位于`lib/upgrade/platform.sh`中，根据产品的型号来判断各自的magic值。

   ```bash
   platform_check_image() {
   	local board=$(ramips_board_name)
   	local magic="$(get_magic_long "$1")"
   
   	[ "$#" -gt 1 ] && return 1
   
   	case "$board" in
   
   	br-6475nd)
   		[ "$magic" != "43535953" ] && {
   			echo "Invalid image type."
   			return 1
   		}
   		return 0
   		;;
   	ubnt-erx)
   		nand_do_platform_check "$board" "$1"
   		return $?;
   		;;
   	mt7621-*)
   		[ "$magic" != "d00dfeed" ] && {
   			echo "Invalid image type."
   			return 1
   		}
   		return 0;
   		;;
   	esac
   
   	echo "Sysupgrade is not yet supported on $board."
   	return 1
   }
   
   ```

   我们一般会在该check函数下面添加私有的校验方式，如固件的验签等功能。

   

2. 保存config配置文件

   ```bash
   export SAVE_CONFIG=1
   ```

   默认的`SAVE_CONFIG`标志为为1，所以默认要保存uci配置文件

   ```bash
   if [ -n "$CONF_IMAGE" ]; then
   	case "$(get_magic_word $CONF_IMAGE cat)" in
   		# .gz files
   		1f8b) ;;
   		*)
   			echo "Invalid config file. Please use only .tar.gz files"
   			exit 1
   		;;
   	esac
   	get_image "$CONF_IMAGE" "cat" > "$CONF_TAR"
   	export SAVE_CONFIG=1
   elif ask_bool $SAVE_CONFIG "Keep config files over reflash"; then
   	[ $TEST -eq 1 ] || do_save_conffiles
   	export SAVE_CONFIG=1
   else
   	export SAVE_CONFIG=0
   fi
   
   ```

    保存config文件函数如下：

   ```bash
   do_save_conffiles() {
   	local conf_tar="${1:-$CONF_TAR}"
   
   	[ -z "$(rootfs_type)" ] && {
   		echo "Cannot save config while running from ramdisk."
   		ask_bool 0 "Abort" && exit
   		return 0
   	}
   	run_hooks "$CONFFILES" $sysupgrade_init_conffiles
   	ask_bool 0 "Edit config file list" && vi "$CONFFILES"
   
   	v "Saving config files..."
   	[ "$VERBOSE" -gt 1 ] && TAR_V="v" || TAR_V=""
   	tar c${TAR_V}zf "$conf_tar" -T "$CONFFILES" 2>/dev/null
   
   	rm -f "$CONFFILES"
   }
   
   
   ```

   如果sysupgrade的时候带参数-n，`sysupgrade -n openwrt-ramips-mt7621-device-squashfs-sysupgrade. bin`，则会将`SAVE_CONFIG=0`

3. run_hooks “” $sysupgrade_pre_upgrade

   这句的意思是：运行函数sysupgrade_pre_upgrade。先介绍下run_hooks函数，定义在文件common.sh中。

   ```bash
   run_hooks() {
       localarg="$1"; shift
       forfunc in "$@"; do
       eval"$func $arg"
       done
   }
   
   ```

   run_hooks函数是钩子函数，其中传过来的第一个参数是函数运行的参数，其余参数为要运行的函数。

   ```bash
   disable_watchdog() {
       killall watchdog
       ( ps | grep -v 'grep' | grep '/dev/watchdog' ) && {
           echo 'Could not disable watchdog'
           return 1
       }   
   }
   
   append sysupgrade_pre_upgrade disable_watchdog
   
   ```

   就是在升级前，去清除watchdog进程

4. ubus call system upgrade

   调用注册到ubus进程的system路径下的update方法，update方法设置了upgrade_running变量值为1，使得在ubus上注册的服务退出时无需等待。

   ```bash
   root@zihome:/usr/sbin# ubus list system -v
   'system' @3b46ff0c
           "board":{}
           "info":{}
           "upgrade":{}
           "watchdog":{"frequency":"Integer","timeout":"Integer","stop":"Boolean"}
           "signal":{"pid":"Integer","signum":"Integer"}
           "nandupgrade":{"path":"String"}
   
   ```

   

5. do_upgrade升级

   ```bash
   if [ -n "$(rootfs_type)" ]; then              
       v "Switching to ramdisk..."                     
       (run_ramfs '. /lib/functions.sh; include /lib/upgrade; do_upgrade') &
   else                                      
       (do_upgrade) &                     
   fi 
   
   ```

   vim /lib/upgrade/common.sh

   ```bash
   do_upgrade() {                                                    
       clear_caches
       v "Performing system upgrade..."
       if type 'platform_do_upgrade' >/dev/null 2>/dev/null; then
               platform_do_upgrade "$ARGV"
       else
               default_do_upgrade "$ARGV"
       fi
   }  
   
   ```

   image升级，保存到对应的mtd分区，这边的PART_NAME在头部会定义为fireware

   ```bash
   default_do_upgrade() {
       sync
       if [ "$SAVE_CONFIG" -eq 1 ]; then
           get_image "$1" "$2" | mtd $MTD_CONFIG_ARGS -j "$CONF_TAR" write - "${PART_NAME:-image}"
       else
           get_image "$1" "$2" | mtd write - "${PART_NAME:-image}"
       fi  
   }
   
   
   ```

   

6. config保存/删除

   保存完固件之后，就开始处理config配置文件

   ```bash
   if [ "$SAVE_CONFIG" -eq 1 ] && type 'platform_copy_config' >/dev/null 2>/dev/null; then
           platform_copy_config
   fi
   
   if [ "$SAVE_CONFIG" -eq 0 ] && type 'platform_remove_config' >/dev/null 2>/dev/null; then
           platform_remove_config
   fi
   
   
   ```

   如果需要保存配置文件，则将config拷贝到/overlay下，`这边的$CONF_TAR压缩包就是上面第二步保存的配置文件

   ```bash
   platform_copy_config() {
       local board_flash=$(mtk_board_flash)
   
       case "$board_flash" in
       "nand"|"spi")
               upgrade_log "Save config"
               rm -rf $1/*
               cp -af "$CONF_TAR" $1/
               sync
               ;;
       esac
   }
   
   
   ```

   如果不需要保存则删除/overlay下的config

   ```bash
   platform_remove_config() {
       local board_flash=$(mtk_board_flash)
   
       case "$board_flash" in
       "nand"|"spi")
               upgrade_log "Drop config"
               rm -rf $1/*
               ;;
       esac
   }
   
   
   ```

   

7. 重启

   ```bash
   v "Upgrade completed"
                                 
   [ -n "$DELAY" ] && sleep "$DELAY" 
   v "Rebooting system..."          
   upgrade_log_end                  
   reboot -f                        
   sleep 2                          
   force_reboot   
   
   ```