sudo: unable to execute /bin/rm: Success

I found a weird error message when I tried to delete some files in my linux box today. The command I used was

sudo rm -rf *.js

to delete some .js files, and I got an error message:

sudo: unable to execute /bin/rm: Success
After googling around, I found this wonderful site, and the solution is to use find coupled with -exec flag rather than rm:
sudo find . -iname '*.js' -exec rm {} \;
The problem is, according to the site, was caused by buffer overflow when expanding the *. 
The single quote that we used in the find command will prevent it from expanding and causing overflow.

So, that's all folks. 

Show memory map of a process

How to show memory map of a process? or how to check how much memory a process is consuming?
Use pmap.

How to use pmap:

1. get a pid of a process you are interested in checking, in this example apache:

   [mainuser@serverone ~]$ ps -eaf | grep http 
   root      1759  4493  0 04:02 ?        00:00:00 /usr/sbin/httpd
   apache    1760  4493  0 04:02 ?        00:00:25 /usr/sbin/httpd
   apache    1761  4493  0 04:02 ?        00:00:23 /usr/sbin/httpd
   apache    1762  4493  0 04:02 ?        00:00:21 /usr/sbin/httpd
   apache    1763  4493  0 04:02 ?        00:00:18 /usr/sbin/httpd

   
   
   
2. run the pmap command against the PID number:
   

   [mainuser@serverone ~]$ sudo pmap 1760 | tail 
   97406000     28K r--s-  /usr/lib/gconv/gconv-modules.cache
   97463000     16K rw---    [ anon ]
   97467000 524288K rw-s-  /tmp/apc.tE1RRo (deleted)
   b7467000  11096K r----  /usr/local/zend/lib/libicudata.so.38
   b7f3d000      4K rw---  /usr/local/zend/lib/libicudata.so.38
   b7f3e000     64K rw-s-  /dev/zero (deleted)
   b7f4e000    504K rw-s-  /dev/zero (deleted)
   b7fcc000     32K rw---    [ anon ]
   bfd74000    144K rwx--    [ stack ]
   total  2742152K

3. The process, which is apache is consuming about 2.7GB of memory

That's all folks :)

How to know if the machine you are working on are a VM

There are a few ways you can detect if the machine you are working on is a VM. Below are commands to use and the output if your machine is a VM:

1. Use dmidecode command, dmidecode is a tool for dumping a computer DMI (some say SMBIOS) table contents in a human-readable format. So if your machine is a vm, you should not get any output:

   [somebody@theserver ~]$ sudo dmidecode
    # dmidecode 2.10
    /dev/mem: mmap: Bad address

2. Try check on /proc/scsi/scsi, if it is a vm, you would not get any attached device:

   [somebody@theserver ~]$ cat /proc/scsi/scsi 
   Attached devices:

   
   
3. Use lspci and see if there is any virtual related devices:

   [somebody@theserver ~]$ /sbin/lspci 
   00:00.0 Host bridge: Intel Corporation 440FX - 82441FX PMC [Natoma] (rev 02)
   00:01.0 ISA bridge: Intel Corporation 82371SB PIIX3 ISA [Natoma/Triton II]
   00:01.1 IDE interface: Intel Corporation 82371SB PIIX3 IDE [Natoma/Triton II]
   00:01.2 USB controller: Intel Corporation 82371SB PIIX3 USB [Natoma/Triton II] (rev 01)
   00:01.3 Bridge: Intel Corporation 82371AB/EB/MB PIIX4 ACPI (rev 03)
   00:02.0 VGA compatible controller: Cirrus Logic GD 5446
   00:03.0 Ethernet controller: Red Hat, Inc Virtio network device
   00:04.0 Ethernet controller: Red Hat, Inc Virtio network device
   00:05.0 SCSI storage controller: Red Hat, Inc Virtio block device
   00:06.0 RAM memory: Red Hat, Inc Virtio memory balloon
   00:07.0 SCSI storage controller: Red Hat, Inc Virtio block device

4. Check on your network interface:

   [somebody@theserver ~]$ /sbin/ethtool -i eth0
   driver: virtio_net
   version: 
   firmware-version: 
   bus-info: virtio0

5. Use dmesg and search for word virt, KVM, vmware, xen:

   [somebody@theserver ~]$ dmesg | grep -i vir
   Booting paravirtualized kernel on KVM
   CPU0: Intel QEMU Virtual CPU version (cpu64-rhel6) stepping 03
   input: Macintosh mouse button emulation as /devices/virtual/input/input1
   virtio-pci 0000:00:03.0: PCI INT A -> Link[LNKC] -> GSI 10 (level, high) -> IRQ 10
   virtio-pci 0000:00:04.0: PCI INT A -> Link[LNKD] -> GSI 11 (level, high) -> IRQ 11
   virtio-pci 0000:00:05.0: PCI INT A -> Link[LNKA] -> GSI 10 (level, high) -> IRQ
   

   [somebody@theserver2:~]$ dmesg | grep -i -e virt
   [    0.000000] Booting paravirtualized kernel on Xen
   [    0.102602] input: Macintosh mouse button emulation as /devices/virtual/input/input0
   [    3.577404] Initialising Xen virtual ethernet driver

   
   

Ping a list of servers

To do this, you need to put all the hosts that need to be checked in a file. For example, I put all my hosts in a file called ping_list:

$ cat ping_list
cat.myhost.net
dog.myhost.net
tiger.myhost.net
bird.myhost.net

There are a few ways to ping multiple hostnames, I'll list out what I have tried before:

1. Use nmap

$ nmap -sP -iL ping_list
Failed to resolve given hostname/IP: cat.myhost.net.  Note that you can't use '/mask' AND '1-4,7,100-' style IP ranges
Failed to resolve given hostname/IP: dog.myhost.net.  Note that you can't use '/mask' AND '1-4,7,100-' style IP ranges
Host 192.168.0.99 is up (0.00036s latency).
Host 192.168.0.100 is up (0.00061s latency).

where -sP is for ping test and -iL is for inputting from files.

2. One liner for loop

$ for i in `cat ping_list`; do ping -c1 $i; done
ping: unknown host cat.myhost.net
ping: unknown host dog.myhost.net
PING tiger.myhost.net (192.168.0.99) 56(84) bytes of data.

--- tiger.myhost.net ping statistics ---
1 packets transmitted, 0 received, 100% packet loss, time 0ms

PING tiger.myhost.net (192.168.0.100) 56(84) bytes of data.
 
 --- bird.myhost.net ping statistics ---
 1 packets transmitted, 0 received, 100% packet loss, time 0ms

I believe there are other tools or scripts beside those I listed above, but I always these 2 methods to ping multiple hosts. If you have other tools or script, please leave a comment.

Thanks

Store svn password

To store your cert and password, all you have to do is:

1. Go to .subversion in your home folder

$ cd ~/.subversion

2. Run below command. This command will add store-auth-creds = yes and store-passwords = yes to your bottom of config file

$ echo -e "store-auth-creds = yes\nstore-passwords = yes" >> config

3. Run any svn command, and choose p for permanent accept certificate, and yes for storing your password.

Now you won't be asked for svn password anymore.