Executing cronjobs on specific days in a month

You can use this post as a reference to schedule the Cronjobs in more Granular fashion.

Situation:

We had a requirement to execute couple of scripts on specific Saturdays of a month throughout the year  i.e., First script (say /opt/firstscript.sh) should be executed on all Saturdays EXCEPT first Saturday of the month, and the Second script (say /opt/secondscript.sh) should be executed ONLY on first Saturday of the month. This we required to do for scheduling Weekly Tape backups.

Executing a script on all Saturdays is fairly simple, we need to just specify number 6 on 5^th column on crontab entry, but here the scenario is different.

The solution for this is shown below. This uses ‘date’ command to check if the current date is a first Saturday of a month.

0  2  *  *  6     [ $(date +%d) -gt 7 ]  && /opt/firstscript.sh               
# Executes at 2am on all Saturdays Except the first Saturday of the month (Saturdays other than 1^st  can fall only after 7^th ).

0  22  *  *  6   [ $(date +%d) -le 7 ]  && /opt/secondscript.sh        

# Executed at 10 PM ONLY on first Saturday of the month (A first Saturday can either be 7^th or less than that ).

Checking NFS and SAMBA shares

NFS

How to check the NFS shares available from a NFS Client ?

#  showmount -e <NFS Server IP>

Example

[root@hostxyz /]# showmount -e nfsserver.domain.com

Export list for nfsserver.domain.com:

/VOL0           stoash01-d3,staat01-d3,rdbash01,10.20.23.16,10.20.64.31,10.100.14.96 ,10.100.16.12 

/VOL1           (everyone)

/ORAAPPS        (everyone)

/ret_vol3       (everyone)

/nas_server_bkp (everyone)

/testnfs        (everyone)

[root@hostxyz /]#

From NFS server, how to find the list of NFS clients accessing the NFS share currently ?

Execute the following script:
for i in `cat /var/lib/nfs/rmtab | awk -F":" '{print $1}' | sort -u`; do nslookup $i | tail -2 | awk '{print $4}'; done

---------------------------------------------------------------------------------------------------------------------------------------------------------
SAMBA

How to find the list of Samba shares available from a Windows Server?

# smbclient -L Samba server IP –Uusername
Password:


[root@hostxyz /]# smbclient -L windows.tcprod.com -Uadevaraju

Password:

Domain=[TCPROD] OS=[Windows Server 2003 R2 3790 Service Pack 2] Server=[Windows Server 2003 R2 5.2]

        Sharename       Type      Comment

        ---------       ----      -------

        IPC$            IPC       Remote IPC

        sqldb_htk       Disk

        webash01-dev    Disk

        C$              Disk      Default share

        VOL3            Disk

        testsmb         Disk

        SMBSYSENG       Disk

        HPUniver.3      Printer   HP Universal Printing PS

        HPUniver.2      Printer   HP Universal Printing PCL 5

        ADMIN$          Disk      Remote Admin

        HPUniver        Printer   HP Universal Printing PCL 6

        print$          Disk      Printer Drivers

        F$              Disk      Default share

        nas_server_bkp  Disk

        SMBVOL1         Disk

        windowsprodbackup Disk

        SMBVOL0         Disk

        Report_server_bkp Disk

        E$              Disk      Default share

        exchange_db     Disk

        sysengdata      Disk


How to mount a Windows Share on to a Linux mount point:


Syntax: 
Put this entry in /etc/fstab and do 'mount -a'
//Windows server IP/Sambashare  /Linux_mount cifs username=XXX,password=XXXX 0 0


Example:
//Windows_server/sambashare      /linux_mnt cifs username=ashok,password=XXXX  0 0

Sudo access to a specific command set

Lets say we have a requirement to give sudo access only to a particular command set.  Let’s take couple of scenarios like this:

1.   We want to give privilege to DBA team to mount/umount ONLY a particular filesystem ( /oracle_data) but  we don’t want them to mount/umount other filesystem.

2.   We want to give privilege to NOC team to start/stop ONLY the httpd service but we don’t want them to start/stop other services.

The syntax in /etc/sudoers file should be as follows:

%dbateam          ALL=(ALL) NOPASSWD:  /bin/mount /oracle_data, /bin/umount /oracle_data

%nocteam          ALL=(ALL) NOPASSWD:  /sbin/service httpd start, /sbin/service httpd stop, /sbin/service httpd status

Having set like this, the respective team members can execute the commands as follows:

# sudo /bin/mount /oracle_data      # Works

# sudo /bin/umount /oracle_data    # Works

# sudo /bin/mount /other_filesystem     # This will fail

# sudo /sbin/service httpd start       #  Works

# sudo /sbin/service httpd stop       #  Works

# sudo /sbin/service httpd restart   #   Fails. Since restart is not specified

# sudo /sbin/service nfs start           #  This will fail

Finding total size of files owned by a particular user

Syntax:

# find <pathname> -user <username> -ls | awk '{sum += $7} END {printf "Total size: %8.4f MB\n", sum/1024/1024}'

Example:

Foldername to search: /nasllm-ih
Username:  rram

[root@hostxyz ~]# find /nasllm-ih -user rram -ls | awk '{sum += $7} END {printf "Total size: %8.4f MB\n", sum/1024/1024}'                   

Total size: 958.7282 MB

[root@hostxyz ~]#

Validation:

Here I have created a folder /root/ashok consists files owned by user “adevaraju” of total size: 160 MB under its various sub-directories.

[root@hostxyz ~]# ls -lRh /root/ashok

/root/ashok:

total 21M

drwxr-xr-x 3 adevaraju root 4.0K Dec 14 06:30 d1

drwxr-xr-x 2 adevaraju root 4.0K Dec 14 06:35 d2

-rw-r--r-- 1 adevaraju root  10M Dec 14 06:21 file1

-rw-r--r-- 1 adevaraju root  10M Dec 14 06:22 file4

/root/ashok/d1:

total 21M

drwxr-xr-x 2 adevaraju root 4.0K Dec 14 06:35 dx

-rw-r--r-- 1 adevaraju root  10M Dec 14 06:22 file2

-rw-r--r-- 1 adevaraju root  10M Dec 14 06:22 file3

/root/ashok/d1/dx:

total 21M

-rw-r--r-- 1 adevaraju root 10M Dec 14 06:30 file5

-rw-r--r-- 1 adevaraju root 10M Dec 14 06:30 file6

/root/ashok/d2:

total 101M

-rw-r--r-- 1 adevaraju root 100M Dec 14 06:30 file7

[root@oralsb11-new ~]#

 [root@oralsb11-new ~]# du -sh ashok/

161M    ashok/

[root@hostxyz ~]# find /root/ashok -user adevaraju -ls | awk '{sum += $7} END {printf "SUM: %8.4f MB\n", sum/1024/1024}'

SUM: 160.0156 MB

[root@hostxyz ~]#

PS: By replacing the search folder to '/', we can find the total size of files owned by a specified user in the entire system.