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Wednesday, May 30, 2012

Bandwidth limitation using "TC Command" RedHat /CentOS/Fedora/Ubuntu/SuSe

Use "tc" command.

# tc qdisc add dev eth0 root tbf limit 15Kb buffer 10Kb/8 rate 10Kbps

Check the configuration.

# tc -s qdisc
qdisc tbf 8001: dev eth0 root refcnt 2 rate 80000bit burst 10Kb lat 512.0ms
Sent 994 bytes 14 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
qdisc pfifo_fast 0: dev eth1 root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
Sent 10861 bytes 156 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
qdisc pfifo_fast 0: dev eth2 root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
Sent 15932 bytes 100 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0
qdisc pfifo_fast 0: dev eth3 root refcnt 2 bands 3 priomap 1 2 2 2 1 2 0 0 1 1 1 1 1 1 1 1
Sent 1836 bytes 10 pkt (dropped 0, overlimits 0 requeues 0)
rate 0bit 0pps backlog 0b 0p requeues 0

If you want to delete the configuration, execute the following command.

# tc qdisc del dev eth0 root

Using dump/restore command do the backup and restore whole CentOS/RedHat/Fedore/SUSE/Ubuntu.

Using dump/restore command do the backup and restore whole CentOS/RedHat/Fedore/SUSE/Ubuntu.

http://dump.sourceforge.net/isdumpdeprecated.html

# cat /etc/fstab
LABEL=/                 /                       ext3    defaults        1 1
LABEL=/boot1            /boot                   ext3    defaults        1 2
LABEL=/data             /data                   ext3    defaults        0 0
tmpfs                   /dev/shm                tmpfs   defaults        0 0
devpts                  /dev/pts                devpts gid=5,mode=620 0 0
sysfs                   /sys                    sysfs   defaults        0 0
proc                    /proc                   proc    defaults        0 0
LABEL=SWAP-sda5         swap                    swap    defaults        0 0

# fdisk -l
   Device Boot    Start      End    Blocks      Id System
/dev/sda1 *           1       13    104391      83 Linux
/dev/sda2            14      1925   15358140    83 Linux
/dev/sda3          1926      3200   10241437+   83 Linux
/dev/sda4          3201      4864   13366080    5   Extended
/dev/sda5          3201      3391   1534176     82 Linux swap / Solaris

# dump -0uf - /dev/sda1 | ssh root@192.168.0.14 dd of=/tmp/sda1.dump
# dump -0uf - /dev/sda2 | ssh root@192.168.0.14 dd of=/tmp/sda2.dump
# dump -0uf - /dev/sda3 | ssh root@192.168.0.14 dd of=/tmp/sda3.dump
# dump -0uf - /dev/sda4 | ssh root@192.168.0.14 dd of=/tmp/sda4.dump
# dump -0uf - /dev/sda5 | ssh root@192.168.0.14 dd of=/tmp/sda5.dump

Restore the data

# restore -rf /sda1.dump
# restore -rf /sda2.dump
# restore -rf /sda3.dump
# restore -rf /sda4.dump
# restore -rf /sda5.dump

Live CD/rescue mode first and use fdisk to create partitions and give ip address

Create a partitions on new disk

Fdisk /dev/sda

format sda1/sda2/sda3/sda5 by using the mkfs command
# mkfs.ext3 /dev/sda1
# mkfs.ext3 /dev/sda2
# mkfs.ext3 /dev/sda3
# mkfs.ext3 /dev/sda4
# mkfs.ext3 /dev/sda5

Re-label all the partitions
# e2label /dev/sda1 /boot1
# e2label /dev/sda2 /
# e2label /dev/sda3 /data
# mkswap -L SWAP-sda5 /dev/sda5

login into 192.168.0.187, and restore sda1 from a remote 192.168.0.14 sda1.dump

# ssh 192.168.0.187 "cd /mnt/sda1 && RSH=/usr/bin/ssh restore -r -f 192.168.0.14:/tmp/sda1.dump"

Please run grub-install in rescue mode first. Install grub on /dev/sda1*

Tuesday, February 14, 2012

RedHat /CentOS Tapes MT command

Working with "mt" Commands: reading and writing to tape.

    The following assumes the tape device is "/dev/st0"

    STEP 1 ( rewind the tape)

         # mt -f /dev/nst0 rewind

    STEP 2 (check to see if you are at block 0)

         # mt -f /dev/nst0 tell
           At block 0.

    STEP 3 (Backup "tar compress"  directories "today"  and "etc")

         # tar -czf /dev/nst0 today  etc

    STEP 4 (Check to see what block you are at)

          # mt -f /dev/nst0 tell

      You should get something like block 2 at this point.

    STEP 5 (Rewind the tape)

          # mt -f /dev/nst0 rewind

    STEP 6 (List the files)

          # tar -tzf /dev/nst0
             today/
             etc/
             
    STEP 7 (Restore directory "one"  into directory "junk").  Note, you
         have to first rewind the tape, since the last operation moved
         ahead 2 blocks. Check this with "mt -f /dev/nst0".

          # cd junk
          # mt -f /dev/nst0 rewind
          # mt -f /dev/nst0 tell
             At block 0.
          # tar -xzf /dev/nst0 today

    STEP 8 (Next, take a look to see what block the tape is at)

          # mt -f /dev/nst0 tell
             At block 2.

    STEP 9 (Now backup directories three  and four)

          # tar -czf /dev/nst0 kd6w2 kd6mtf

      After backing up the files, the tape should be past block 2.
      Check this.

          # mt -f /dev/nst0 tell
            At block 4.

         Currently the following exist:

               At block 1:
                    today/
                   etc/
                   kd6w2/

               At block 2:
                   kd5mtf

                 At block 4:
                   (* This is empty *)

    A few notes. You can set the blocking factor and a label
    with tar.


     $ tar --label="temp label" --create  --blocking-factor=128 --file=/dev/nst0 Notes

    But note if you try to read it with the default, incorrect blocking
    factor, then, you will get the following error:

       $ tar -t   --file=/dev/nst0
       tar: /dev/nst0: Cannot read: Cannot allocate memory
       tar: At beginning of tape, quitting now
       tar: Error is not recoverable: exiting now

    However this is easily fixed with the correct blocking factor

        $ mt -f /dev/nst0 rewind
        $ tar -t --blocking-factor=128 --file=/dev/nst0
        workingdir testarea
        conf.txt

    Take advantage of the label command.

        $ MYCOMMENTS="tape"
        $ tar --label="$(date +%F)"+"${MYCOMMENTS}"

    Writing to tape on a remote 192.168.56.5 computer

        $ tar cvzf - ./tmp | ssh -l rajat 192.168.56.5 '(mt -f /dev/nst0 rewind; dd of=/dev/st0 )'

    Restoring the contents from tape on a remote computer

        $ ssh -l rajat 192.168.56.5 '(mt -f /dev/nst0 rewind; dd if=/dev/st0  )'|tar xzf -

    Getting data off of tape with dd command with odd blocking factor. Just set ibs very high

        $ mt -f /dev/nst0 rewind
        $ tar --label="Contenets of Notes" --create  --blocking-factor=128 --file=/dev/nst0 Notes
        $ mt -f /dev/nst0 rewind
        $ dd ibs=1048576 if=/dev/st0 of=notes.tar

    The above will probably work with ibs=64k as well