Linux is for everybody. Lets enjoy it.
This is for searching any string in vi or vim, regardless of the case. All you need to do is to press
/\c
while you are in vim followed by your pattern to start this ignore case search. For example, if you have a list like below:/\cmiu
, vi will list every line as the search output, even though the cases are different. try it :)Sometimes you want to see what version of a package is available on a repo, below is how you do it:
[humans@earth]$ sudo yum list subversion --showduplicates Loaded plugins: fastestmirror Loading mirror speeds from cached hostfile * base: dist1.800hosting.com * epel: mirror.steadfast.net * extras: centos.mirror.lstn.net * rpmforge: mirror.us.leaseweb.net * updates: mirror.raystedman.net Installed Packages subversion.x86_64 1.6.11-10.el5_8 installed Available Packages subversion.i386 1.6.11-7.el5_6.4 base subversion.x86_64 1.6.11-7.el5_6.4 base subversion.i386 1.6.11-10.el5_8 updates subversion.x86_64 1.6.11-10.el5_8 updates
This is useful, if you need to add some modification to your searched string in sed, but you are using regex and you do not know what the output would be. Please see below example:
$ echo "123 123 abc abc" | sed 's/[0-9]*/(&)/'
(123) 123 abc abc
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 *.jsto delete some .js files, and I got an error message:
sudo: unable to execute /bin/rm: SuccessAfter 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.
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:
[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
[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
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:
[somebody@theserver ~]$ sudo dmidecode
# dmidecode 2.10
/dev/mem: mmap: Bad address
[somebody@theserver ~]$ cat /proc/scsi/scsi
Attached 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
[somebody@theserver ~]$ /sbin/ethtool -i eth0
driver: virtio_net
version:
firmware-version:
bus-info: virtio0
[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
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_listThere are a few ways to ping multiple hostnames, I'll list out what I have tried before:
cat.myhost.net
dog.myhost.net
tiger.myhost.net
bird.myhost.net
$ nmap -sP -iL ping_listwhere -sP is for ping test and -iL is for inputting from files.
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).
$ for i in `cat ping_list`; do ping -c1 $i; doneI 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.
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
