openwrt编译报错，dd的bs参数没了

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1. dd if=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin of=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin.new bs= conv=sync
   
2. dd: invalid number: ''
   
3. make[5]: *** [Makefile:208: /opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin] Error 1
   
4. make[5]: Leaving directory '/opt/tsxor/openwrt/openwrt/target/linux/ramips/image'
   
5. make[4]: *** [Makefile:23: install] Error 2
   
6. make[4]: Leaving directory '/opt/tsxor/openwrt/openwrt/target/linux/ramips'
   
7. make[3]: *** [Makefile:11: install] Error 2
   
8. make[3]: Leaving directory '/opt/tsxor/openwrt/openwrt/target/linux'
   
9. time: target/linux/install#87.20#25.25#106.18
   
10.     ERROR: target/linux failed to build.
    
11. make[2]: *** [target/Makefile:25: target/linux/install] Error 1
    
12. make[2]: Leaving directory '/opt/tsxor/openwrt/openwrt'
    
13. make[1]: *** [target/Makefile:19: /opt/tsxor/openwrt/openwrt/staging_dir/target-mipsel_24kc_musl/stamp/.target_install] Error 2
    
14. make[1]: Leaving directory '/opt/tsxor/openwrt/openwrt'
    
15. make: *** [/opt/tsxor/openwrt/openwrt/include/toplevel.mk:230：world] 错误 2

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我认为问题在

1. dd
   
2. if=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin
   
3. 
   
4. of=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin.new
   
5. bs= conv=sync
   
6. dd: invalid number: ''

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如上，dd的bs参数没了，可能是这个参数通过变量定义，然后变量错误了，然而我也不知道这个dd是在哪个脚本里执行的，有什么头绪吗

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地方找到了，可是给我整不会了：
是include/image.mk的：

1. define Image/pad-to
   
2.         dd if=$(1) of=$(1).new bs=$(2) conv=sync
   
3.         mv $(1).new $(1)
   
4. endef

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23***

用了一个小trick过了这个错误，把上一楼提到的代码的bs参数去掉
百度了一下发现bs只影响dd写入速度，应该不会影响写入结果

1. define Image/pad-to
   
2.         #dd if=$(1) of=$(1).new bs=$(2) conv=sync
   
3.         dd if=$(1) of=$(1).new conv=sync && echo $(2)
   
4.         mv $(1).new $(1)
   
5. endef
   

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于是过了：

1. #dd if=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin of=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin.new bs= conv=sync
   
2. dd if=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin of=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin.new conv=sync && echo
   
3. 4477+1 records in
   
4. 4478+0 records out
   
5. 4585472 bytes (4.6 MB, 4.4 MiB) copied, 0.0268627 s, 171 MB/s
   
6. tar: Option --mtime: Treating date '@1650113974' as 2022-04-16 12:59:34
   
7. sysupgrade-zte_e8820s/
   
8. sysupgrade-zte_e8820s/CONTROL
   
9. sysupgrade-zte_e8820s/kernel
   
10. sysupgrade-zte_e8820s/root
    
11. 4744+1 records in
    
12. 4745+0 records out
    
13. 2429440 bytes (2.4 MB, 2.3 MiB) copied, 0.0200686 s, 121 MB/s

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这样应该是过编译了吧？

1. Signing package index...
   
2. make[2]: Leaving directory '/opt/tsxor/openwrt/openwrt'
   
3. export MAKEFLAGS= ;make -w -r json_overview_image_info
   
4. make[2]: Entering directory '/opt/tsxor/openwrt/openwrt'
   
5. make[2]: Nothing to be done for 'json_overview_image_info'.
   
6. make[2]: Leaving directory '/opt/tsxor/openwrt/openwrt'
   
7. export MAKEFLAGS= ;make -w -r checksum
   
8. make[2]: Entering directory '/opt/tsxor/openwrt/openwrt'
   
9. make[2]: Leaving directory '/opt/tsxor/openwrt/openwrt'
   
10. make[1]: Leaving directory '/opt/tsxor/openwrt/openwrt'

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23***

讲一下找到include/image.mk的过程，水个经验
看发生错误的命令：

1. dd if=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin of=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin.new bs= conv=sync

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分析一下，原命令应该长这样：（这是伪代码）

1. dd if=[path1] of=[path2] bs=[variable] conv=sync

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虽然我也怀疑conv=sync中的sync也是变量定义，但是我还是姑且猜他是被写死的
于是在openwrt的github repo中搜索带conv=sync的code
target/linux/mpc85xx/image/p1020.mk，target/linux/apm821xx/image/Makefile等文件有这段，但是我直接排除，因为我编的是mt7621
剩下的文件中，进行人工筛选，看conv=sync前面是否有bs=[variable]
然后剩下俩：
scripts/combined-image.sh

1. # Make sure provided images are 64k aligned.
   
2. kern="${IMAGE}.kernel"
   
3. root="${IMAGE}.rootfs"
   
4. dd if="$1" of="$kern" bs=$BLKSZ conv=sync 2>/dev/null
   
5. dd if="$2" of="$root" bs=$BLKSZ conv=sync 2>/dev/null

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以及2楼那段。
再看看出错的命令的if和of选项：

1. if=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin
   
2. of=/opt/tsxor/openwrt/openwrt/build_dir/target-mipsel_24kc_musl/linux-ramips_mt7621/tmp/openwrt-ramips-mt7621-zte_e8820s-squashfs-factory.bin.new

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发现就差一个.new
再看看2楼那段的if和of选项：

1. if=$(1)
   
2. of=$(1).new

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实锤了，就是它！（2楼那段的if和of选项的意思就是of比if多个.new）
然后就开改

怎么样，逆向思维，很神奇吧