linux guide

DUMP and RESTORE:
Dump and Restore is used to take backup or restore ‘only ext2 or ext3’ file system. This
particular dump and restore utility can be u sed to take full or incremental backup.
To take a full backup of the /home filesystem onto the tape device nst1 we can use the
following command –
dump -0u-f /dev/nst0 /home
Here we specify 0 to define full backup and u (dump -0u-f /dev/nst0 /home)
is specified so that dump information will be recorded for future use of dump. Generally
administrators love to take full backup on weekly or monthly basis while regularly take
incremental backup. For incremental backup, the command may be as follows –
dump -4u-f /dev/nst0 /home
Please note, we use 4 instead of 0 to define incremental backup.
To restore data backed up with dump command we use restore command. For example,
suppose we had /dev/hda9 mounted on /home. On a clean device mounted on /home,
first of all we should change the working directory there and then use the following
command – restore –rf /dev/nst0
Whenever we use dump command using –u option, it will update /etc/dumpdates, which
actually contents the dump-information.

SOME BACKUP RELATED COMMANDS:

To Erase Dat Drive
mt –f /dev/st0 erase
To rewind the Dat Drive
mt –f /dev/st0 rewind
To backup the www Server
find /etc/httpd/conf /usr/local –print | cpio –ovcB > /dev/st0
To backup up Sendmail Mail Server
find /var /home /etc/mail –print | cpio –ovcB > /dev/st0

Labels: backup, command, drive, dump, erase, file system, Linux, mail server, Proxy server, restore, sendmail

Using the ‘at’ utility. The at facilty is designed to run jobs at specific times. Submitted jobs are spooled to /var/spool/at directory.
The daemon name is atd. Access Control Files:
/etc/at.allow - Contains list of users who are granted to submit ‘at’ jobs.
/etc/at.deny - Contains list of users who have ‘No’ permission to submit ‘at’ jobs.
Let us see how can we use the ‘at’ facility. For Example, we need to copy the contents of /home directory in compressed form to /tmp/backup directory.
To do this, we can run the following commands –
at 12:00
cd /home
mkdir /tmp/home
mkdir /tmp/backup
cp –Rf * /tmp/home
cd /tmp/home
tar czvf backup.tar.gz *
cp backup.tar.gz /tmp/backup
+d
We can also run a single command to make this happen – this command will do the same task above.
echo “cd /home; mkdir /tmp/home; mkdir /tmp/backup; cp –Rf * /tmp/home; cd
/tmp/home; tar czvf backup.tar.gz *; cp backup.tar.gz /tmp/backup” | at 12:00
Example for specifying times for at jobs:
at now The job will run immediately
at now + 2 minutes The job will run 2 minutes from the current time.
at next hour The job will run after 1 hour from the current time.
at next month The job will run after 1 month from the current time.
at next year The job will run after 1 year from the current time.
at next fri The job will run on next Friday
at 16:00 today The job will run today at 16 hours.
at 16:00 tomorrow The job will run tomorrow at 16 hours
at 16:00 May 31 2004 The job will run on May 31s t , 2004 at 16 hours
I think, the most efficient way to use the at facility with –f option.
• f option can be used to use contents of a file to executed as ‘at’ command.
For Example, if we use the following command –
at –f /home/newback now + 10 hours
The system will see the contents of the /home/newback file and use them as ‘at’ command

Labels: at command, backup, command, corn, job, Linux, SCHEDULING, TASKS, unix