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Charlweed
Asked: 2017-05-04 19:26:26 +0800 CST

/bin and /usr/bin set to 400, way to fix without live disk?

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We have a minor disaster on a Centos7 system. A bug in a config script recursively set /, /bin, and /usr/bin, to 400 permissions. This means that basic commands like, chmod, mount, and almost everything else is un-executable. I'm pretty confident I can fix this by booting from a live-usb, but I'd have to make one. Also, the damaged machine is our router, so when it goes down, we lose our internet access.

I have another box with linux x64 binaries for chmod, bash, mount and the rest, is there some clever way to execute them from a usb (or the network or whatever) without rebooting?

linux

1 Answers

  1. Best Answer

    On centos7 64 bit, the ld program is located at /lib64/ld-2.17.so. I would not have found it unless I had another centos7 system running. I used the binary ld-2.17.so to execute /bin/chmod , and fixed /bin, /usr/bin, and /bin/chmod. That was enough to allow me to start correcting everything else. On the other centos system, I ran:

    for dir in /* ; do getfacl -pR "$dir" > /root/"$dir"_acls.txt  ; done

    This gave me references on what the correct permissions are for my distro. I copied these txt files to the damaged system, and the for bin,boot,dev,etc, and home, I ran

    for perm in /root/perms/*_acls.txt ; do setfacl --restore $perm ; done

    This was not an exact match in files, but it is much better than doing every file at once, or every file individually.

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