Inadvertently nuked my disk permission structure - why?

permissions chown

5,599

Solution 1

This happened because you used:

sudo chown -R root:www-data .*

when you should have used this instead:

sudo chown -R root:www-data ./*

First, -R is recursive for all directories under the target directory.

Additionally, * will match all files and directories under the current directory. Next, .* will match all files and directories one level above the current directory.

To avoid this in the future, you can use the ls command to verify the path before you execute the chown command like in these examples:

ls -a ./*
ls -a *
ls -a .*
ls -a ../*

Another way to avoid this is to always use the full path to the directory you wish to run a command to.

Here is an example:

sudo chown -R root:www-data /opt/*

Edit:

You can use the following command to chmod all hidden files or directories directly under /opt (assuming the first character after the . that makes them hidden is a letter, a number, a dash or an underscore which should be true for most files).

for i in /opt/.[A-Za-z0-9-_]*; do sudo chmod root:www-data "/opt/$i"; done

You can verify what files this will chmod by running the following command:

ls /opt/.[A-Za-z0-9-_]*

The first part of the command: for i in /opt/.[A-Za-z0-9-_]* says that, for all the results of the glob /opt/.[A-Za-z0-9-_]* assign each result to the variable "i".

The glob here says that the first character must be . and that the next character [A-Za-z0-9-_] must be any character that is A-Z or a-z or any number 0-9 or a - or a _.

This will exclude the results . and .. which represent the current directory and the directory above the current directory and will only include hidden files and directories.

The second part of the command: do sudo chmod root:www-data "/opt/$i" says to run the command for all variables that match the current value of $i.

The third part of the command: done says that I am finished.

Additionally, you used the -R option with chmod and the -R option is recursive and will apply to all directories and files.

When you only only use the chmod command with no options, the command will only apply to the specific file or directory you gave it and will not apply recursively to directories.

Solution 2

The shell glob .* matches .. (the parent directory) in this case unfortunately that's /:

steeldriver@t400s:/opt$ ls .*
.:

..:
bin  boot  cdrom  dev  etc  home  initrd.img  initrd.img.old  lib  lib32  lib64
libx32  lost+found  media  mnt  opt  proc  root  run  sbin  snap  srv  swapfile  sys
tmp  usr  var  vmlinuz  vmlinuz.old

For additional discussion see:

Solution 3

Your troubles came because .* matches everything that begins with a dot. The context is the current directory, since this expression does not include a path. So, if there are any hidden files or folders like .git in the current directory, you'll match them. But (as you'll see by running ls -a in that folder), you will also match . and ..

And .., of course, is the parent directory, so chmod -R recursively targeted everything in the parent directory.

5,599

Duke Dougal

Updated on September 18, 2022

Comments

Duke Dougal almost 2 years

I was trying to chown within /opt and for some reason chown jumped up to the parent and chowned everything.

Can anyone suggest why/how this might happen, and how to avoid doing it in future? It's a bit concerning that running a command in a given dir can effectively jump up and run it in root dir.

ubuntu: /opt > sudo chown -R root:www-data .*
chown: changing ownership of '../var/lib/lxcfs/proc/cpuinfo': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/proc/meminfo': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/proc/stat': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/proc/uptime': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/proc/diskstats': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/proc/swaps': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/proc': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/devices': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/blkio': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/hugetlb': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/rdma': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/pids': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/freezer': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/cpuset': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/memory': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/perf_event': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/cpu,cpuacct': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/net_cls,net_prio': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/name=systemd': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup/unified': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs/cgroup': Operation not permitted
chown: changing ownership of '../var/lib/lxcfs': No such file or directory
^C
:ubuntu: /opt >

Joshua Besneatte almost 5 years

I would have done it like this: sudo chown -R root:wwwdata /opt as per the --help dialog... perhaps using that pipe caused some issue???
Duke Dougal almost 5 years

I figure it's something to do with me specifying dotstar .*
steeldriver almost 5 years

.* matches .. (the parent directory, which is /) - see Does “chmod 777 .* -R” chmod parent directories (..)?
Joshua Besneatte almost 5 years

dotStar... too close to a deathStar to be safe :/
Joshua Besneatte almost 5 years

@steeldriver that sounds like it should be posted as an answer ;)
Duke Dougal almost 5 years

Hmmm. So presumably the entire system is now in a somewhat unknown state and I should restore/rebuild?
Duke Dougal almost 5 years

So what is the correct way to set permissions on hidden files, which is what I was trying to do?
mchid almost 5 years

@DukeDougal See here: askubuntu.com/q/43621/167115
Monty Harder almost 5 years

@JoshuaBesneatte I try to avoid running recursive commands on arguments beginning with / because most keyboards put / fairly close to the Enter key, and it's too easy to accidentally hit Enter before typing the rest of the command. To mitigate this risk, one can either cd to the root directory and omit the leaing /, or start the command with (, which means the command won't be executed until the matching ) is typed, giving the opportunity to hit Ctrl-C and bail out of a bad mistake (such as rm -rf /tmp/foo-install and hitting Enter instead of T).
Joshua Besneatte almost 5 years

@MontyHarder Excellent tip! Thanks!

Duke Dougal almost 5 years

My intent was to target hidden files. I mistakenly assumed that the syntax used for grepping hidden files as described here stackoverflow.com/questions/10375689/… is generally valid syntax for hidden files. Seems not.
mchid almost 5 years

@DukeDougal The problem with that answer you have is that it also matches . and .. which represent the current directory and the directory above your current directory as well as hidden files.
Giacomo Alzetta almost 5 years

@DukeDougal You shouldn't accept the first answer that comes up right away. It's generally better to wait, say, 24 hours before accepting. In that time other more useful or better written answers may come up that would deserve accepting. You can upvote all answers you think are useful. StackExchange is not (or should not be) about "who answers first" but "who provides the best answer" (both in terms of content and clarity).
ilkkachu almost 5 years

should this answer perhaps explain why, exactly using .* is wrong here? (And well, you could also use chmod -R . instead of chmod -R ./*, but of course they're also slightly different...)
val is still with Monica almost 5 years

Edit is terrible. It suggests to parse ls output and is very slow while answer is to use find.
Scott almost 5 years

(1) No wildcard (glob/pattern) is recursive in bash except for **, and even that has to be explicitly enabled. IMHO, you should be clearer about the role of -R. (2) People are advised to avoid using plain * because it can match filenames beginning with -, which will then be interpreted as options. command -- * should protect against that, but I’m not sure all commands honor that convention. … (Cont’d)
Scott almost 5 years

(Cont’d) … (3) *, ./* and even /opt/* fail to find “dot files” (.*) unless the dotglob option is set. As Joshua Besneatte and ilkkachu say, chown -R /opt and chown -R . are better. … (Cont’d)
abligh almost 5 years

This is the correct, and much simpler, answer
marcelm almost 5 years

@DukeDougal "I mistakenly assumed that the syntax used for grepping hidden files as described here … is generally valid syntax for hidden files." - Actually, this problem also exists for grep (because it's nothing to do with chmod and grep, it's bash's fault for including .. in globbing .*). This is pointed out by the cumments below the accepted answer!
alexis almost 5 years

This analysis is incorrect. The command is only recursive because -R means "recursive" to chmod. And .* does not mean what you say it means.
wjandrea almost 5 years

Are you aware of ls -A? It will automatically exclude . and ... Regardless though, don't parse ls.
terdon almost 5 years

@val please see the latest edit. There's no reason to use find for something like that. A (proper) shell loop is fine. It might be slower, yes, but on modern machines and for manually run commands the difference will be negligible.
rexkogitans almost 5 years

I don't get it. A day after and this answer is still totally wrong. * is not recursive.
terdon almost 5 years

@rexkogitans it is when used with chmod /path/*: that will cause chmod to change the permission of path and all files and directories under it. So it is recursive in that sense. Compare it to chmod /path/ which will only change the permissions of /path and nothing under it.
Peter Cordes almost 5 years

An absolute path like /opt/.* wouldn't help, /opt/.. is the same as .. with CWD = /opt.
mchid almost 5 years

@wjandrea Thanks, I was not aware because I have an alias set for ls where ls=ls -a.
rexkogitans almost 5 years

@terdon Shell glob of * is not recursive, butchmod with the switch -R is.
alexis almost 5 years

@Peter: Yes, that is correct: If the expression included a path, that would give the context (the starting point), instead of it being the current directory. The OP meant to use . as the context, but it didn't work out that way due to the missing slash...
terdon almost 5 years

@rexkogitans yes, but chmod dir/* is also recursive since that will change the permissions of the contents of dir. I'm not saying that * is recursive, I'm saying that dir/* will cause a command to recurse one level down into dir.
rexkogitans almost 5 years

@terdon This is not what the word "recursion" means, because also this shell glob is not recursive.