/usr dir with all permissions denied even from root

Question

First, I ran:

sudo chmod -R -777 /usr

Now, my /usr dir permissions looks like this:

d---------

So nobody has permissions I can't even get in the dir or run bash commands.

-777=000. The command you used changed the permissions of /usr and all subdirectories and files in /usr to 000 recursively. It's hard to replicate the original schema of /usr. I think OS reinstallation is the only solution unless somebody else can replicate the exact permissions of files and sub-folders of /usr — Kulfy, Nov 03 '19 at 17:47
I agree with Kulfy. Re-install w/o formatting is the quickest way to get a working system. And please don't do that again "Now, my /usr dir permissions looks like this: d---------" that is exactly what you asked it to do ;-) — Rinzwind, Nov 03 '19 at 17:53
@Kulfy If I'm not mistaken, /usr is all 755. If there is any way to change to 755 you will be good. — mchid, Nov 03 '19 at 17:53
@mchid Right. /usr has 755. But what about the files in it? For example: /usr/bin/sudo has -rwsr-xr-x, /usr/include/glob.h has 644. IMO this can't be achieved in one shot. Remember permissions were changed recursively — Kulfy, Nov 03 '19 at 17:57
@mchid no -but- those that are 644 might not mind being 755 Kulfy in 2 you can set 755 for dirs and 644 for files but it is a system directory. I would still just reinstall w/o a format. Probably the easiest method with the most desired result — Rinzwind, Nov 03 '19 at 17:58
I will agree with the reinstallation is the best steps for this. Yes, the folder of /usr is 755, however, there is a lot of SUIDs and other special permissions of files in that folder and the subfolders that need to be set. — Terrance, Nov 03 '19 at 17:58
Possible duplicate of Set myself as owner of /etc with chown command now getting all kinds of errors (see terdon's answer and What if I accidentally run command chmod -R on system directories — Zanna, Nov 03 '19 at 17:59
@Rinzwind I now see there is a lot of lib files that are not 755. Re-install without formatting is probably best. At least you get to keep the home directory. — mchid, Nov 03 '19 at 17:59
@mchid indeed but those all seem to be 644. That is easily set with a find (1 for dirs, 1 for files). — Rinzwind, Nov 03 '19 at 18:00
all the different permissions I have in /usr (this command took several minutes to run) — Zanna, Nov 03 '19 at 18:10

score 1 · Answer 1 · answered Nov 03 '19 at 18:16

This shows all the different file permissions in /usr, that you'd have to change back:

walt@bat:~(0)$ sudo find /usr -xdev -print0 | xargs -0 -r -n 1000 sudo stat --format="%A" | sort | uniq -c | sort -rn
 440550 -rw-r--r--
  86783 lrwxrwxrwx
  51877 drwxr-xr-x
  16293 -r--r--r--
   8060 -rwxr-xr-x
   1174 drwxrwxr-x
    461 -rw-rw-r--
    363 -r-xr-xr-x
     28 -rwxrwxr-x
     22 drwxrwsr-x
     17 -rwxr-sr-x
     16 -rwsr-xr-x
      6 -rwxr--r--
      4 -rwsr-sr-x
      2 -r-xr-sr-x
      2 -r-xr--r--
      2 -rwsr-xr--
      1 -rwxr-xr--
      1 -rwx------
      1 drwxrwsr-t

This shows all the permissions AND ownerships in /usr that you would have to change back:

walt@bat:~(0)$ sudo find /usr -xdev -print0 | xargs -0 -r -n 1000 sudo stat --format="%A %U:%G" | sort | uniq -c | sort -rn
[sudo] password for walt: 
 440517 -rw-r--r-- root:root
  86783 lrwxrwxrwx root:root
  51870 drwxr-xr-x root:root
  16293 -r--r--r-- root:root
   8058 -rwxr-xr-x root:root
   1174 drwxrwxr-x root:root
    461 -rw-rw-r-- root:root
    363 -r-xr-xr-x root:root
     33 -rw-r--r-- walt:walt
     28 -rwxrwxr-x root:root
     22 drwxrwsr-x root:staff
     16 -rwsr-xr-x root:root
      6 -rwxr-sr-x root:mail
      6 -rwxr--r-- root:root
      6 drwxr-xr-x walt:walt
      3 -rwxr-sr-x root:tty
      2 -r-xr-sr-x root:postdrop
      2 -r-xr--r-- root:root
      2 -rwxr-xr-x walt:walt
      2 -rwxr-sr-x root:utmp
      2 -rwxr-sr-x root:shadow
      2 -rwsr-sr-x root:root
      1 -rwxr-xr-- root:wireshark
      1 -rwxr-sr-x root:ssh
      1 -rwxr-sr-x root:mlocate
      1 -rwxr-sr-x root:games
      1 -rwxr-sr-x root:crontab
      1 -rwx------ root:root
      1 -rwsr-xr-- root:messagebus
      1 -rwsr-xr-- root:dip
      1 -rwsr-sr-x root:mail
      1 -rwsr-sr-x daemon:daemon
      1 drwxr-xr-x walt:root
      1 drwxrwsr-t root:lpadmin

You have stirred your system with a root stick. It's broken. Reinstall, and don't do that.

The following answer (in the comments) explains how to install without formatting so that you can maybe keep your home directory. However, you should always make a backup just in case, of course. https://askubuntu.com/a/270045/167115 — mchid, Nov 03 '19 at 18:26

/usr dir with all permissions denied even from root

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