How do I make read-only file system writable?

using opensuse
Thanks
--Glenn

steps done so far:

# mount /dev/sdb /media/disk

# df -h
Filesystem Size Used Avail Use% Mounted on
/dev/sdb 1.8T 747G 1.0T 43% /media/disk

# id
uid=0(root) gid=0(root) groups=0(root)

# ll /media/disk
ls: cannot access /media/disk/nvidia-installer.log: No such file or directory
ls: cannot access /media/disk/opensuseurl.txt: No such file or directory
ls: cannot access /media/disk/packman.txt: No such file or directory
ls: cannot access /media/disk/q1.txt: No such file or directory
ls: cannot access /media/disk/q1.txt~: No such file or directory
ls: cannot access /media/disk/read-only,txt: No such file or directory
ls: cannot access /media/disk/remove.txt: No such file or directory
ls: cannot access /media/disk/repos.txt: No such file or directory
ls: cannot access /media/disk/rpmlist.log: No such file or directory
ls: cannot access /media/disk/to-remove: No such file or directory
ls: cannot access /media/disk/x: No such file or directory
ls: cannot access /media/disk/zgl: No such file or directory
ls: cannot access /media/disk/lost_name_2a:73746200000000:3f1ed: No such file or directory
ls: cannot access /media/disk/pub_linux_utils_fs_reiser4_libaal.html: No such file or directory
total 180
drwx------ 4 root root 4 Sep 5 15:42 .Trash-0
lrwxrwxrwx 1 root root 55 Jul 5 2009 NVIDIA-Linux-x86_64-185.18.14-pkg2.run -> nvidia/laptop-7x/NVIDIA-Linux-x86_64-185.18.14-pkg2.run

drwxr-xr-x 2 root root 863 Feb 22 2010 packages
drwxr-xr-x 5 root root 14 May 14 2011 packman
?????????? ? ? ? ? ? packman.txt
drwxr-xr-x 3 root root 4 Aug 11 2009 partitioning
drwxr-xr-x 7 root root 17 Nov 3 2009 phoronix
drwxr-xr-x 2 root root 3 Mar 15 2011 pictures
drwxr-xr-x 3 root root 4 Sep 23 2009 plugins
?????????? ? ? ? ? ? pub_linux_utils_fs_reiser4_libaal.html
?????????? ? ? ? ? ? q1.txt
?????????? ? ? ? ? ? q1.txt~
?????????? ? ? ? ? ? read-only,txt
?????????? ? ? ? ? ? remove.txt
?????????? ? ? ? ? ? repos.txt
drwxr-xr-x 3 root root 4 Jan 25 2010 rpm-description
drwxr-xr-x 4 root root 8 Sep 23 2009 rpm-help
?????????? ? ? ? ? ? rpmlist.log
drwxr-xr-x 2 root root 22 Jul 22 2010 rpms-old
drwxr-xr-x 2 root root 4 Jun 3 2011 sharon
?????????? ? ? ? ? ? to-remove
?????????? ? ? ? ? ? x
?????????? ? ? ? ? ? zgl
drwxr-xr-x 2 root root 6 Jul 20 2011 zz-iso


# echo zzzzzzzzzz >/media/disk/zjunk.txt
bash: /media/disk/zjunk.txt: Read-only file system


#

The filesystem on that disk is damaged, and the kernel will refuse to make it writable until it has been repaired by fsck. Judging from what you have shown, fsck might result in losing a lot of data. If that data is important, you should use ddrescue to copy as much of the image as can be recovered to a new 2TB (or larger) disk drive before you play with it.

Fix the filesystem. Although read-only so you can fix it while "using" it, semi-safely. Otherwise push the I'm feeling lucky button. Systemd will default to read-only for / if / isn't listed in /etc/fstab.

$ sudo mount -o remount,rw /

Where / is the mount point that is (ro,...) in the output of mount without parameters, that you want to change.

$ mount

As soon as the kernel detects an error in the filesystem it will be remounted read-only again. There is an "error behavior" field in the filesystem super block. It is typically set to "remount-ro". You can use tune2fs to change it. The other options are "continue" and "panic". Changing it to "continue" is not recommended. Writing to a corrupted filesystem is like using a rotary lawnmower in a meadow where there are cow droppings. Cr*p gets spread around and makes the problem much worse.

Do what the others have suggested would be better.

modded due to mis understanding of question

File permissions have absolutely nothing to do with a "Read-only filesystem" error. And anyway, attempting to change permissions on such a filesystem would just fail with a "Read-only filesystem" error.

If you do that you will make all of your programs not executable.

----------------------------------
Steve Stites

@BW-userx, you seem to have formed a pattern of posting snide, sarcastic and off-topic remarks in a variety of threads. This isn't acceptable at LQ. Please refrain from this behavior moving forward. If you have any questions, feel free to contact a mod or myself privately. Thanks.

--jeremy

2 members found this post helpful.

I would suggest censoring/removing that chmod command from this thread as it is very dangerous and destructive and wrong. A beginner might happen upon it and run it. I'm reporting it as such to the mods.

shouldn't you have done... (and NOBODY RUN THIS)

.c.h.m.o.d. ugo+w / -R

still a terrible idea to actually run of course but at least you can actually do things in directories and don't lose all of your executes on all of your commands. Of course this doesn't fix a certain issue I once had to deal with where somebody did (ANOTHER ONE TO NEVER RUN)

c.h.a.t.t.r. +i /

Needless to say I think this has gone off topic enough now.

It seems that many have seen my answer and not my recommendations to same said answer, beginner or not one has to learn this eventually. that being so then when? the person then will always be in the dark about that command, then perhaps one day find out the hard way, by actually doing that to his or her system.

I explicitly said
"But I'd not recommend that."

which then raises a question.

why not?

which promotes what?

thinking.
which does what, especially if one asks more questions or seek the answers to these questions?
gains knowledge.

If one keeps treating a child as a child he will always act like a child.
If one treats a child like an adult (within that child limits) he will become an adult.

and even adults act like children sometimes, that is called regression.


How some people love to take things out of content so they can fire up their torches and scream burn him burn him...

just one additional comment:
on a read-only filesystem the chmod command will not do anything but fail.

"Gentlebeings, let us stay 'on point' here ..."

Another situation where you can encounter a read-only filesystem is when you boot a "rescue" DVD or USB-stick, and when you boot into single-user mode. The file system, although undamaged, might be initially be purposely mounted Read/Only so that it requires a conscious act ("remounting it") to subject its content to change. (Think: "the safety on a gun.")

Glenn - if, in fact, there is damage to the file system on the medium in question, the above-quoted recommendation is the best one so far, in my opinion, for the reason mentioned by rknichols. I wouldn't recommend any other file-system repair commands until you have made an image of the disk with ddrescue.

Best of luck !