I get automatically logged out instantly after logging in

Question

In ubuntu terminal whenever I try to log in it instantly logs me out. On one account it just logs me out for no reason and on all other accounts it says

Could not chdir to home directory /home/tom: Permission denied
/bin/bash: Permission denied
Connection to 192.168.0.58 closed.

Beforehand I ran the command sudo chmod 700 / This means that I can't run any commands and am trapped on the login screen because no users have access to any files.

How do I fix this? I'm on a Raspberry PI so I can't use the GRUB recovery system. Thanks in advance, Tom

Have you changed permissions/ownership of directories system-wide? ... Have you copied users' home directories with sudo? ... Explain what you did before this had happened. — Raffa, Jul 16 '22 at 16:53
Yeah... i did 'sudo chmod / 700' I read permission codes wrong — Tomsoz, Jul 16 '22 at 16:57
Well, it's clearly logging you out for a very good reason: You don't have correct permission anymore. Edit your question to ask your REAL question which is "I did X, now how do I fix all the damage that I caused?" The more information you provide in your Question (not in comments), the more useful answers you will get. — user535733, Jul 16 '22 at 17:38
Does this answer your question? What if I accidentally run command "chmod -R" on system directories (/, /etc, ...) — Pilot6, Jul 16 '22 at 18:45

Raffa · Answer 1 · 2022-07-17T07:59:36.357

sudo chmod 700 / is a bad idea but, should be completely(Assuming you did only and exactly that ... i.e. you did not use chmod -R nor change ownership with chown) recoverable ... A 700 permissions on / will deny other users all rights(read, write and execute) and allow only the owner(root) ... Hence the message you see and the behavior you experience because only the user root can access the system root directory / and no other user can even read that directory or anything under it.

The default permissions for the root directory / are 755:

Permissions     Owner  Group  
755(drwxr-xr-x) root   root   /

Therefore you need to boot into recovery mode, drop to a root shell(Alternatively, boot into a live USB, mount your root partition and chroot to it) then change the permissions back like so:

chmod 755 /

then reboot and try to login normally again.

If you make it and login back successfully ... You might want to check system directories permissions and compare them to another intact Ubuntu system and fix what might need fixing if there are any ... Below is the information of directories and files under / for reference:

Permissions       Owner Group Name               Linked to
777   lrwxrwxrwx  root  root  '/bin'         ->  'usr/bin'
755   drwxr-xr-x  root  root  '/boot'            
775   drwxrwxr-x  root  root  '/cdrom'           
755   drwxr-xr-x  root  root  '/dev'             
755   drwxr-xr-x  root  root  '/etc'             
755   drwxr-xr-x  root  root  '/home'            
777   lrwxrwxrwx  root  root  '/lib'         ->  'usr/lib'
777   lrwxrwxrwx  root  root  '/lib32'       ->  'usr/lib32'
777   lrwxrwxrwx  root  root  '/lib64'       ->  'usr/lib64'
777   lrwxrwxrwx  root  root  '/libx32'      ->  'usr/libx32'
700   drwx------  root  root  '/lost+found'      
755   drwxr-xr-x  root  root  '/media'           
755   drwxr-xr-x  root  root  '/mnt'             
755   drwxr-xr-x  root  root  '/opt'             
555   dr-xr-xr-x  root  root  '/proc'            
700   drwx------  root  root  '/root'            
755   drwxr-xr-x  root  root  '/run'             
777   lrwxrwxrwx  root  root  '/sbin'        ->  'usr/sbin'
755   drwxr-xr-x  root  root  '/snap'            
755   drwxr-xr-x  root  root  '/srv'             
600   -rw-------  root  root  '/swapfile'        
555   dr-xr-xr-x  root  root  '/sys'             
1777  drwxrwxrwt  root  root  '/tmp'             
755   drwxr-xr-x  root  root  '/usr'             
755   drwxr-xr-x  root  root  '/var'

@user535733 Thanks ... added those to the answer ... Although they should be OK if it was just chmod with no -R option passed ... "complete recovery" hopefully :-) — Raffa, Jul 16 '22 at 18:27
I can't use the ubuntu GRUB recovery menu because I'm on a rasperry pi and they don't support GRUB. — Tomsoz, Jul 16 '22 at 21:18

I get automatically logged out instantly after logging in

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