Archive for category Linux/Unix

Returning linux timestamp

To return linux timestamp use the following:

Date and time now in timestamp format:
date "+%s"

A specific date and time in timestamp format:

date -d "<time>" "+%s"
e.g. date <del>d "2014</del>01-30 15:00:00" "+%s"

Date and time now in timestamp format and nano seconds:

date "+%s%N"

Date and time now in timestamp format and milli seconds:

date “+%s%N” | cut -b1-13
echo $(($(date “+%s%N”)/1000000))

To return a specific date and time in timestamp with nano or milli seconds then simply add -d parameter similar to the previous example.

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How to convert Scientific Notation number to Decimal using bash?

Turns out this is pretty easy to do using awk and printf in bash!

Lets say you have a scientific value of “2.1061863333e+03” and you wish to convert it to decimal. You can do something like below:

>> echo "2.1061863333e+03" | awk {' printf "%12.2fn",$1 '}

  • Obviously you can do the same if you have series of values in a file using cat.
  • I found this specially useful when obtaining values from RRDs.

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Need to modify linux filesystem when mounted in read-only?

In cases where you’re at the Repair Filesystem prompt and need to modify one or more files to fix what is broken then you can mount the root in read-write mode to avoid needing the rescue disk. Otherwise the disk is mounted in read-only mode and you’re unable to modify any files.

The following command will mount the root in read-write mode:

mount -w -o remount /

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SELinux basic commands

Get a list of all rules currently applied:
getsebool -a

Set a SELinux rule:
setsebool -P <rule_name>=X where X is 0 for OFF and 1 for ON</rule_name>

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VSFTPD on CentOS – Unable to list files or directories


  • Running VSFTPD on CentOS

  • The FTP port is opened through IPTables

  • Authenticating using the user credentials works

  • XferLog doesn’t provide any specific details


  • Checkout /var/log/messages for any hints as to the problem

  • SELinux is blocking the FTP daemon from listing the home directory. Use setsebool -P ftp_home_dir=1 to relax the rule in SELinux

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MySQL – Backup Script

Great Backup script.


  1. Shell script to backup MySql database
  2. To backup Nysql databases file to /backup dir and later pick up by your
  3. script. You can skip few databases from backup too.
  4. For more info please see (Installation info):
  6. Last updated: Aug - 2005
  7. --------------------------------------------------------------------
  8. This is a free shell script under GNU GPL version 2.0 or above
  9. Copyright (C) 2004, 2005 nixCraft project
  10. Feedback/comment/suggestions :
  11. -------------------------------------------------------------------------
  12. This script is part of nixCraft shell script collection (NSSC)
  13. Visit for more information.
  14. -------------------------------------------------------------------------

MyHOST="localhost" # Hostname

  1. Linux bin paths, change this if it can not be autodetected via which command
    MYSQL="$(which mysql)"
    MYSQLDUMP="$(which mysqldump)"
    CHOWN="$(which chown)"
    CHMOD="$(which chmod)"
    GZIP="$(which gzip)"
  1. Backup Dest directory, change this if you have someother location
  1. Main directory where backup will be stored
  1. Get hostname
  1. Get data in dd-mm-yyyy format
    NOW="$(date +"%d-%m-%Y")"
  1. File to store current backup file
  2. Store list of databases
  1. DO NOT BACKUP these databases

[ ! -d $MBD ] && mkdir -p $MBD || :

  1. Only root can access it!
    $CHOWN 0.0 -R $DEST
    $CHMOD 0600 $DEST
  1. Get all database list first
    DBS="$($MYSQL -u $MyUSER -h $MyHOST -p$MyPASS -Bse 'show databases')"

for db in $DBS

skipdb=-1 if [ "$IGGY" != "" ]; then
for i in $IGGY
do [ "$db" "$i" ] && skipdb=1 || :
done fi if [ "$skipdb" “-1” ] ; then
  1. do all inone job in pipe,
  2. connect to mysql using mysqldump for select mysql database
  3. and pipe it out to gz file in backup dir :)
$MYSQLDUMP -u $MyUSER -h $MyHOST -p$MyPASS $db | $GZIP -9 > $FILE fi

Cron Job:
@daily /path/to/

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iSCSI discovery fails with FreeNAS

Error Messages:

Windows Server 2008:
Connection Failed
The iSCSI name specified contains invalid characters or is too long.

This issue drove me crazy. I checked the firewall, connectivity, event viewer but didn’t come across anything that would indicate the real problem. I finally checked the log for FreeNAS and didn’t see anything that would indicate what is the problem. After a reboot on the Windows machine and trying again the following warning message showed up in the log which shed light on the issue:

FreeNAS Log:
istgt[2330]: istgt_lu.c:1232:istgt_lu_add_unit: ***WARNING*** TargetName contains an invalid character.

As you can see in the error message I had named the target as SQL_Log and it looks like the underscore caused the problem! Removed the underscore and fixed the issue..

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How to set up FreeNAS with VMWare

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ProFTPD: getting terminated once a week

Once a week on Monday morning when I would come to work the ProFTPD process on one of my linux boxes (Fedora) had terminated and I had to restart the service to get it going. After checking the logs I found that it happened exactly 2AM on Monday morning every week. The following was the error I was getting in the logs:

received SIGHUP -- master server reparsing configuration file

After a bit of research I found that the process was included in the /etc/logrotate.d directory and what was happening was that the logrotate was attempting to rename the log file, compress it and create a new one however that seemed to crash the ProFTPD server. Removed the proftpd entry from the directory and resolved the issue.

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VSFTPd: Configuration variables

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