Ubuntu – Cannot change directory into home directory, although permissions are set correct

chmodpermissionsUbuntuunix

I guess I need some help from an advanced Unix user…

On a Ubuntu System I did something stupid. I typed sudo chmod 774 .* or the like, in a subfolder of my home folder and then I suddenly could not change the directory to my home directory anymore.
I'm not quite sure about the exact numbers in the command, but I am sure about the .*.

Now, after a reboot, I can't even log into the GUI anymore and when I Ctrl + Alt + F1 into a console and log in, I get the message No directory, logging in with HOME=/.

When I then try to cd into /home/myusername, I get the error: -bash: cd: /home/myusername: Permission denied. Also, ls can't access the folder.

I checked the permissions of /home/myusername using sudo, and they are all correctly set to:

drwxr-xr-x 25 myusername myusername 4096 Aug 26 17:30 myusername

A testuser, that I created, has the same promblems. It cannot log into the GUI, either. Only a guest session can do it (I guess that is because the guest home folder is created inside /tmp).

What do I need to do, to restore my permissions/get access to my home folder again??? Any suggestions?

Cheers, Sebastian

Best Answer

So, you own your home direcory /home/myusername, and have rwx permissions on it.

But a
cd /home/myusername
gives a Permission denied?

That looks like you are not allowed to look at /home in the to begin with, before it comes to actually looking up myusername in that directory.

With
sudo chmod 774 .*
in /home/myusername, you included the file ...
And /home/myusername/.. is the same as /home.

The permissions were applied as root, so the 4 is what applies to you a a normal user. this is r--, it does not contain the execute permission. On a directory, the execute permission is what allows you to look inside the directory.

The problem applies to all users that have their home directory under /home, as you already found out.

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The /sys directory in Linux is deceptive. Unlike most other directories, it does not provide persistent storage for arbitrary files.

Rather, it's a way to look at the systems's devices - their states and configurations. These files go away between boots and are dynamically generated by your system at startup. It is normal to be denied permission to write new files or directories there, even as root. You can detect these filesystems by viewing the mount type:

$ mount
none on /dev/pts type devpts (rw,nosuid,noexec,relatime,mode=600)
none on /proc type proc (rw,nosuid,nodev,noexec,relatime)
none on /sys type sysfs (rw,nosuid,nodev,noexec,relatime)
none on /proc/sys/fs/binfmt_misc type binfmt_misc (rw,nosuid,nodev,noexec,relatime)
none on /sys/fs/fuse/connections type fusectl (rw,relatime)
none on /run type tmpfs (rw,nosuid,noexec,relatime,size=3284248k,mode=755)
/dev/md2 on /home type ext4 (rw,relatime,user_xattr,acl,barrier=1,data=ordered,discard)

devpts, proc, sysfs, binfmt_misc, and fusectl are all dynamically generated filesystems that reflect internal system information, and aren't for normal filesystem use. You will likely get permission denied errors even as root or other issues if you try to use these as a normal filesystem.
tmpfs is a temporary filesystem which resides within RAM - You can write to here and use it like a normal filesystem, but anything saved here will be erased as soon as the computer shuts down. Copy your files elsewhere if you want to save them.
ext4 is an actual filesystem on a device somewhere. Data saved here will be preserved like you would expect on a harddisk. There are many filesystems, but the key note is how this line has /dev/md2 instead of none: none means that there is no device backing the filesystem - it doesn't really exist, and is entirely virtual. If a mount point has an actual device (like /dev/sda1 or /dev/md1), then that means the contents actually exist on a device somewhere.

Would you be able to put your edited files in another directory? Or do you specifically mean to edit the configuration of a device?

Best Answer

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