Useful Linux Commands

Command to find files accessed in last 30 days. will find files that is accessed in last 30 days, under root folder.
# find / type f -atime -30
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List contents of a folder along with contents of its subfolder. But it will traverse only to a depth of one. ie, it will not show the contents of subfolder's subfolder.
# ls *
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To print the iptables rules along with line number.
# iptables -L --line-numbers
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To find a particular rule with rule number #; where # is the rule number you want to list
# iptables -L OUTPUT --line-numbers | grep ^#
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Change permission only for folders
# find . -type d -exec chmod 755 {} \;
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List with 777 permission
#find . -type d -perm 777
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To list all the processes listening to port 80
# lsof -i TCP:80|awk {'print $2'}
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To kill all the process listening to apache port 443/80
# lsof -i TCP:443|awk {'print $2'} | xargs kill -9
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Recursively chmod only directories
find . -type d -exec chmod 755 {} \;
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Recursively set the execute bit on every directory
chmod -R a+X *
The +X flag sets the execute bit on directories only
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Recursively chmod only files
find . -type f -exec chmod 644 {} \;
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Recursively chmod only PHP files (with extension .php)
find . -type f -name '*.php' -exec chmod 644 {} \;
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Find all files in /home/user/demo directory
$ find /home/user/demo -print
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Now find all files in /home/user/demo directory with permission 777
$ find /home/user/demo -perm 777 -print
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Next you need to apply chmod on all these files using -exec option:
$ find /home/user/demo -perm 777 -print -exec chmod 755 {} \;
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Command to find files modified on July 12
ll|grep dr|awk '{print $9}' > 123
for i in `cat 123`;do ls -ld $i;done|grep "Jul 12"
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How to See the SSH password guesses

First, find the PID of the listening SSH daemon process:
# ps axuww | egrep 'PID|ssh'
Now become root and attach to the running daemon with strace:
# strace -f -e 'read,write' -p12345
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Yum issues. TypeError: rpmdb open failed

Yum issues.

While giving the command "yum list " getting the error

==========================================================
Loaded plugins: fastestmirror
error: no dbpath has been set
error: cannot open Packages database in /%{_dbpath}
Traceback (most recent call last):
File "/usr/bin/yum", line 29, in ?
yummain.user_main(sys.argv[1:], exit_code=True)
File "/usr/share/yum-cli/yummain.py", line 229, in user_main
errcode = main(args)
File "/usr/share/yum-cli/yummain.py", line 84, in main
base.getOptionsConfig(args)
File "/usr/share/yum-cli/cli.py", line 184, in getOptionsConfig
enabled_plugins=self.optparser._splitArg(opts.enableplugins))
File "/usr/lib/python2.4/site-packages/yum/__init__.py", line 191, in _getConfig
self._conf = config.readMainConfig(startupconf)
File "/usr/lib/python2.4/site-packages/yum/config.py", line 754, in readMainConfig
yumvars['releasever'] = _getsysver(startupconf.installroot, startupconf.distroverpkg)
File "/usr/lib/python2.4/site-packages/yum/config.py", line 824, in _getsysver
idx = ts.dbMatch('provides', distroverpkg)
TypeError: rpmdb open failed
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Solution

#rm /dev/urandom
#mknod -m 644 /dev/urandom c 1 9

that should solve problem

until second VPS reboot...

----
stop VPS
mknod --mode 644 /vz/private/100/lib/udev/devices/urandom c 1 9
start VPS

Your issue should fix your issue
For more reference you can use the link http://forum.openvz.org