Can't change permissions; "read-only filesystem"

Gustin Johnson gustin at
Thu Jul 24 01:03:13 BST 2008

Hash: SHA1

Paul DeShaw wrote:
| I wrote:
|     pad at Studio909:~$ ls -l /media
|     total 12<snip>
|     drwxrwxrwx  1 root root   19 2008-06-22 22:46 PPA1.2
|     drwxr-xr-x 21 root root 4096 2008-07-09 09:22 UbuntuStudio
|     PPA1.2 is the external drive; UbuntuStudio is the old semi-broken
|     installation.  I can mount it and access files, like the permissions
|     indicate.  But on PPA1.2, I get messeges saying I don't have the
|     permissions, even though it's rwx all the way across.
|     I will mess with that later.
| I've been messing with it.  When I try to cheat and use the GUI file
| browser as root,
| I can't make any of these sessions read-and-write. (Right-clicking on
| "properties", then clicking the "permissions" tab, lets you change
| permissions in a GUI file browser).  I get an error; 'cannot change
| permissions to something.wav  Read-only file system' Either a .wav file
| or a file with a name like
| "93992436libardourvampplugins:perusssionsets:2" will get this error.  I
| will get out my Linux command book tomorrow and try to use chmod and/or
| chown to see if it works any better.
| These same files and folders are now suddenly read-only on my other
| installation, which had full access before I did the new install.  I had
| the drive plugged in when I ran the install.  Could that be the reason?
| They are owned by pad, which is the user name I'm using on the new

The name is not as important as the UID.  What UID does "pad" have in
/etc/passwd  I make sure that my username has the same uid accross all
three systems at home.  Of course it helps that they are all Debian
derived so this is not usually a problem.

| installation as well.  Curiously, files owned by 99 are read-and-write.
| These are sessions I started in Ardour under Mac OS X; I don't know why
| the owner is 99, because there is no user account on any system I use
| called '99'.   But I set the permissions in OS X so that 'others' has

This is probably the UID, not the username.  It was likely set by
another system that has a user with a UID of 99.  Your current system
probably does not have a user with that UID hence it just shows the UID.

grep for your username in /etc/passwd, it will show your UID (probably
1000 if it is the first user you created).

| read and write access.  At least one of these sessions now works
| everywhere, including the new install.

What does the entry in /etc/fstab say about this disk?  Also, what file
system are you using on the external drive?  It sounds like NTFS from
the problems you described.  That or you have enabled extended ACLs.
man getfacl/setfacl is your friend here.

You could always mount the drive the with umask option:
mount -t <fstype> /dev/disk/by-id/<disk name>-part<#> /path/to/mount -o

You can also put the umask option in /etc/fstab
| Every time I fix something, something else breaks, and I never end up
| with a useable system.  I started building this system in the summer of
| '06, and still haven't been able to really use it.  Is this some kind of
| record?

That is how I got into computers in the first place.  I once broke my
Dad's laptop, and a friend showed me how to fix it (recreate
autoexec.bat).  I have been breaking things in new ways on different
platforms ever since.
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