Sim Link Or A Better Option

Hello,
We have been having a nightmare of a time with a crash on one of our file shares.

We finally were able to recover the logical volume group and get the path to return. However it appears its mapping is off.

dmsetup status
vg_flood-sff_sha
vg_os-lv_tmp: 0 10485760 linear
vg_os-lv_usr: 0 20971520 linear
vg_os-lv_var: 0 10485760 linear
vg_os-lv_opt: 0 41943040 linear
vg_os-lv_swap: 0 16777216 linear
vg_os-lv_root: 0 10485760 linear


dm6 I would guess is where /dev/mapper/vg_flood-sff_share needs to be mapped to, as it is the only one without mapping. As you can see dmsetup also shows this logical volume as different than the rest.

I am trying to figure out how to fix the mapping for this so that I can activate the logical volume and get our data back.

Please forgive me but I'm a little new to Red Hat (RHEL 5). I'm using rysnc to backup critical data and to a second disk; here is what I'm typing at the command line rsync -rvgal /data/disk1/share /data/backup/share. It appears that the softlinks are not transfered to the backup drive and some of the links point to data not located in the source folder (/data/share). After reading the rsync man page I was a little confused about the L option (vs the l option). In order to ensure that the linked files are moved should I type the below:

rsync -rvgaL /data/disk1/share /data/backup/share

A million thanks,
Johnny Mac

Hi,

I am trying to understand the difference between char devices and block devices.
I understand the basic, which is that char devices input/output data one character at a time, whereas block device input/output data block by block. But for char device driver, most of the time we are able to read/write an array of data using the read/write system call. This "array of data" sounds like a block of data to me, except that it's not fixed in size as for block devices. With this thinking, can I say that I can effectively achieve block read/write with a char device driver?
And what are the other differences?

Thank you all,
Wei

Hello everyone,

I recently had an issue where I lost my whole backup server due to an electrical overload causing my server to literally explode and fried all 4 of my terabyte drives.... needless to say, I have no more backups because of this, and everywhere I read about backups said that setting up a raid array would allow me to keep good backups.... boy did I learn this lesson the hard way in needing to have some sort of external backup option, which brings me to this post and my questions:

I'm using Ubuntu 14.04 LTS server on an older Dell Poweredge 600sc, and I was thinking of using WD Passport 1Tb external drives to be used as my "offsite" backup option. I don't have a lot of data, and my current backup schedule is only a weekly backup, so thinking that if I have two of these passport drives so that I can have one drive offsite and one attached to the server, and rotate them every 4 weeks so as not to loose all my data.

Here's my question: Ideally, I would love to just be able to unplug the current drive, plug in the new drive and have everything work. However, I don't see this actually working, but if there's a way to do this, that would be totally awesome.... ;-)

So, realistically, I know I will have to unmount the one drive, unplug it, then plug in the new drive and mount it on the system. Is there a way to mount this to the same mount point automatically so that I don't have to rewrite my backup script each time I swap drives out so that the backups go to the same mount point? Or will the UUID's get messed up each time I do this?

Hopefully this makes sense and an easy solution can be found to accomodate this idea.....

Thanks again for all your help. This site is awesome for newbies such as myself........

Mikey

Hi All,
I had installed Cent OS 6.6 on sda. The RAID1 and LVM setup was on sdb and sdc. To practice well on recovering RAID and LVM after the OS reinstallation, I just reinstalled the OS. During first re installation of OS, I had selected all the mount points including RAID/LVM partitions as same as how those where mounted before the reinstallation, but the format was selected to only /, /others, /var. And after booting /dev/md0 and LVM partitions were set to active automatically and everything was mounted properly. Also there was no any data loss in the RAID/LVM partitions. So I could made sure that everything will be perfect if we carefully select the mount points during OS reinstallation by making sure the formating partitions.

Now I thouht of reinstalling OS once again but this time didn't select mount points for RAID/LVM partitions during OS reinstallation, thought for manual setup after the installation. So just selected /, /others, /var partitions to format. When it booted, I ran "cat /proc/mdstat" but it was taken /dev/md127(read only) instead of /dev/md0.
Code:

# cat /proc/mdstat 
Personalities : [raid1] 
md127 : active (auto-read-only) raid1 sdc[1] sdb[0]
      52396032 blocks super 1.2 [2/2] [UU]
      
unused devices: <none>

So now I just wanted to stop and restart this RAID array as /dev/md0. But I am not able to stop as it is giving following error.
Code:

# mdadm --stop --force /dev/md127
mdadm: Cannot get exclusive access to /dev/md127:Perhaps a running process, mounted filesystem or active volume group?

I made sure that no one RAID/LVM partitions are mounted.
Code:

# df -h
Filesystem      Size  Used Avail Use% Mounted on
/dev/sda1        15G  3.5G   11G  26% /
tmpfs           376M     0  376M   0% /dev/shm
/dev/sda2       4.7G  9.8M  4.5G   1% /others
/dev/sda3       2.9G  133M  2.6G   5% /var

But LVM is active
Code:

# pvdisplay 
  --- Physical volume ---
  PV Name               /dev/md127
  VG Name               data
  PV Size               49.97 GiB / not usable 4.00 MiB
  Allocatable           yes 
  PE Size               4.00 MiB
  Total PE              12791
  Free PE               5111
  Allocated PE          7680
  PV UUID               IJ2br8-SWHW-cf1d-89Fr-EEw9-IJME-1BpfSj
   
# vgdisplay 
  --- Volume group ---
  VG Name               data
  System ID             
  Format                lvm2
  Metadata Areas        1
  Metadata Sequence No  19
  VG Access             read/write
  VG Status             resizable
  MAX LV                0
  Cur LV                2
  Open LV               0
  Max PV                0
  Cur PV                1
  Act PV                1
  VG Size               49.96 GiB
  PE Size               4.00 MiB
  Total PE              12791
  Alloc PE / Size       7680 / 30.00 GiB
  Free  PE / Size       5111 / 19.96 GiB
  VG UUID               982ay8-ljWY-kiPB-JY7F-pIu2-87uN-iplPEQ
   
# lvdisplay 
  --- Logical volume ---
  LV Path                /dev/data/home
  LV Name                home
  VG Name                data
  LV UUID                OAQp25-Q1TH-rekd-b3n2-mOkC-Zgyt-3fX2If
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                10.00 GiB
  Current LE             2560
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:0
   
  --- Logical volume ---
  LV Path                /dev/data/backup
  LV Name                backup
  VG Name                data
  LV UUID                Uq6rhX-AvPN-GaNe-zevB-k3iB-Uz0m-TssjCg
  LV Write Access        read/write
  LV Status              available
  # open                 0
  LV Size                20.00 GiB
  Current LE             5120
  Segments               1
  Allocation             inherit
  Read ahead sectors     auto
  - currently set to     256
  Block device           253:1

As LVM is active on /dev/md127 it is not allowing to stop /dev/md127 raid array. So as I am fresher in RAID/LVM, expecting your kind help to make LVM inactive without any data loss and restart the RAID array as /dev/md0 and then re activate the LVM setup.
Expecting your kind reply, Thanks.

I tried adding two users in apache group and given 775 permission to Document root but user is not able to write into files in DocumentRoot

Tried adding user and DocumentRoot Folder in sudo file but not able to do it recursively

please help


Thanks for reply,
I have already given chmod 775 -R DocumentRoot - for recursively writting permission
You have told to add user in www-data group and chmod 775 -R to DocumentRoot
usermod -a -G www-data <user1>

How can users in www-data can able to write in DocumentRoot which has apache:apache owner and group
please clarify...

Done below steps to solve this:
1) I have created a new group webdata and added required users in this group
2) set sticky bit to document root with below command
setfacl -m g:webdata:rwx -R /path/to/documentroot/
this command will set rwx permission to DocumentRoot so that members in webdata can have full access but still DocumentRoot user and group will be apache

Please tell me for shell script..
I m writing the script.
In that script i written the 1 function and in that function i have to write the contents in existing file
so i write,
cat > /etc/puppet/manifests/init.pp
{
ensure => present,
}
.
But it caanot write the changes in ssh machine
so what i can do in my script?
Please help me...

we do have a record buffer in awk utility that holds one complete record of a data file.

I want to know that if record buffer changes during script processing, then when are these changes reflected back to the data file?

Are they reflected immediately or is there an in-built mechanism available to schedule this change?

Hi,
I am trying to write to usb flash drive using a C program. I have just created some files in USB device and doing my tasks using fopen,fread and fwrite on those files. I was just wondering what is the standard data rate that can be achieved using fwrite() on a file in usb. Secondly what is better way of transferring data to USB flash drive using C Program? Obviously I am a newbie

Regards
AB

Hi All,

I have Redhat5.3 running on my machine. I have 800 GB data mounted on /dev/sdb1 partition. When I reboot my machine and after reboot the data is not available in /data folder. I have already use mount command but its not working.

Can anyone help me how to retrieve those data.