Linking directories

[Amiel Tutolo]

I am going to create a new /usr called /usr so that I can move some of the directories there. My question is how do I link the directories correctly? Do you copy the files first, link the directories and then remove the ones you copied? I just need some steps to follow. I have done this in a lab setting but not in the real world. Thanks

[Steven E. Protter · Accepted solution]

move the files first then do a hard or soft link with the ln command

SEP

[A. Clay Stephenson]

Typically, /usr is a filesystem rather than a simple directory so that you would create a new filesystem (on a new logical volume), mount the new filesystem as /usr2, cpio all the files in /usr to the new /usr2. I would then alter /etc/fstab and mount the new filesystem as /usr.

If all you want to do is mount some directories (possibly in a different filesystem) under /usr then the key to this is the symbolic (soft) link.

e.g.


ln -s /newfs/newdir /usr/flea
ln -s /newfs2/newdir2 /usr/dog

Now /usr/dog will point to /newfs2/newdir2 and this redirection will be invisible to the application.

[Sridhar Bhaskarla]

Hi,

If this new filesystem is going to be part of another volume group, then I would suggest you to pay attention to the directories that you would like to link. Typically you may want to keep bin,lib,sbin etc., in /usr as during the external storage maintaince, you will have the basic /usr functionality available. If you have any software like backup etc, you can probably create them under new filesystem and create softlinks.

Create a newfilesystem and mount it as /usr1
Make sure you have the corresponding entry in /etc/fstab.

#cp -Rp /usr/local /usr1/local
#du -sk /usr1/local

once contents are properly copied, create links

#rm -rf /usr/local
#ln -s /usr1/local /usr/local

YOu better do it in single user mode so that you will not affect the OS or application.

-Sri

[Amiel Tutolo]

Ok. In my question I said /usr twice. What I meant was a a new fs called /usr2. So I guess I would create filesystem /usr2, copy the directories and files I want from /usr, then using the ln command do the following
ln /usr/xxx /usr/xxx
Am I correct or way off?

[Jeff Schussele]

Hi,

You simply can't have TWO filesystems mounted to /usr at the same time.

If I understand you correctly you want to move dirs *under* /usr to another filesystem. In that case, I think the proper way to do this is to fbackup the data in those dirs & then delete the files in the filesystems in those dirs. Beforehand you would have created the new LV/FS structure & now mount them to /usr/dir1, /usr/dir2 & frecover that data back into these newly created filesystems.

I guess you could also temp mount the new filesystems to some other location, copy the data from /usr/dir1, /usr/dir2, etc to /usr/temp1, /usr/temp2, etc. THEN empty /usr/dir1, /usr/dir2, etc. & umount /usr/temp1, /usr/temp2, etc & then remount them to the newly emptied /usr/dir1, /usr/dir2, etc.

In both scenarios don't forget to edit /etc/fstab for these new mounts.

My 2 cents,
Jeff

[Sridhar Bhaskarla]

HI,

No. You cannot have two /usr filesystems. So, linking from /usr to another /usr is not possible.

-Sri

[Amiel Tutolo]

OK. In my second post I said .usr twice again. I need skinnier fingers. I meant that the link command chould look like this:
ln /usr/xxx /usr2/xxx

Sorry if I am confusing nayone. I don't want to screw this up and have to go to an ignite tape.

[Sridhar Bhaskarla]

Hi,

Use 'ln -s' as indicated

ln -s source destination

To create a link from /usr1/local to /usr/local, you would run the command

ln -s /usr1/local /usr/local

ll /usr/local

lrwxr-xr-x 1 root sys 14 Jan 23 16:03 /usr/local -> /usr1/local

As the man page says, ln does not create hardlinks between filesystems.

-Sri

[A. Clay Stephenson]

No, you blew it again:

ln /usr/xxx /usr2/xxx
should be:
ln -s /usr2/xxx /usr/xxx

That will have the effect of whenever you cd to /usr/xxx, you will actually cd to /usr2/xxx. Man ls for details and pay particular attention to the -s option.

As an aside, it is not required than /usr be on the boot disk or even in vg00 for that matter. The only LVOL's which must be on the boot disk are /, /stand, and primary swap. I wouldn't want to move /usr out of vg00 but it's not a requirement.

[Michael Schulte zur Sur]

Hi,

may I ask you, why you want to move things out of /usr? It looks to me, you are running out of space there, right? Be careful anyway, what you put there. You certainly don't want the machine to get stuck at bottup.

Michael

[Amiel Tutolo]

I am running low on space and I don't see anything I can just remove. I was going to move directories like old, examples, and openv to new filesystem (usr2) and then link them back to usr. If I can get some downtime I was just going to extend the filesystem. It doesn't seem to grow much except for when out DBA forgets about cleaning out his mail. Of course I just go in and delete it all.

[James A. Donovan]

As far as /usr/openv is concerned, I've moved the netbackup files under /opt (where they belong, dammit! ;-)), and created a link under /usr.

So if you have the room under /opt, I would suggest...

# mv /usr/openv /opt
# ln -s /opt/openv /usr/.

Netbackup still runs prefectly fine, and the netbackup logs don't fill up my /usr filesystem.

[Michael Schulte zur Sur]

Hi,

can you post as attachment du -k /usr so we can see, where space is used?

Michael

[A. Clay Stephenson]

/usr is one of those filesystems that should remain all but fixed in size once a system has stabilized. Your mention of mail is a glaring problem. There should be a symbolic link to /var/mail from /usr/mail so that all transient activity (like mail) actually occurs in /var. Likewise, /usr/tmp should be be soft-linked to /var/tmp.

[Amiel Tutolo]

Attached is the du -k /usr. Thanks for everyones help. I will assign points by Monday.

[Michael Schulte zur Sur]

Hi,

do you really need chinese, korean and japanese fonts? They gobble up a lot of space.

Michael