Category: Computer Tips

Modern DHCP server will identify clients using its MAC address, such that if you are offline (shutdown the client computer) for a short period, like a few hours, up to a few days, depends on the load of the dhcp server and the pool size, when you are back online again, you will get the […]

First the system has the following system mounting points /proc, /sys, /dev, /dev/shm, /dev/pts, mounted properly. However, in some OS, the file /usr/libexec/pt_chown has the permission -rws–x–x This seems not working in the chroot subsystem. By changing the permission of the file /$chroot_root/usr/libexec/pt_chown to -rwsr-xr-x screen works in chroot system.

command $(cat filelist)

sed ‘:a;N;$!ba;s/\n/ /g’ infile > outfile

The fix for this is pretty easy and clear – just do #unset DISPLAY before ssh-ing.

tar –selinux –acls –xattrs -cvfz file.tgz yourfiles Where, –selinux – Save the SELinux context to the archive called file.tgz. –acls – Save the ACLs to the archive called file.tgz. –xattrs – Save the user/root xattrs to the archive called file.tgz Please that it archive all extended attributes, including SELinux and ACLs. -c – Create a […]

route add -net x.x.x.0/24 gw y.y.y.y

linux version 2.1 – 2.3.2 Openvpn client start failed (shown), but interestingly it is still working. Workaround: Seems something is racing. add ; sleep 1 after $openvpn –daemon –writepid $piddir/$bn.pid –config $c –cd $work $script_security resolves this. This is to allow one more seconds for the daemon to return success signal.

SCSI scan for single device: echo “c t l” > /sys/class/scsi_host/hosth/scan The older form of this command, echo “scsi add-single-device 0 0 0 0” > /proc/scsi/scsi, is deprecated. SCSI delete single device: echo 1 > /sys/class/scsi_device/h:c:t:l/device/delete The old method echo “scsi remove-single-device h c t l” > /proc/scsi/scsi is depreciated.

yum clean all mkdir CentOS_downloads cd CentOS_downloads wget http://www.gtlib.gatech.edu/pub/centos/6.4/os/x86_64/Packages/centos-release-6-4.el6.centos.10.x86_64.rpm wget http://www.gtlib.gatech.edu/pub/centos/6.4/os/x86_64/RPM-GPG-KEY-CentOS-6 wget http://www.gtlib.gatech.edu/pub/centos/6.4/os/x86_64/Packages/yum-3.2.29-40.el6.centos.noarch.rpm wget http://www.gtlib.gatech.edu/pub/centos/6.4/os/x86_64/Packages/yum-plugin-fastestmirror-1.1.30-14.el6.noarch.rpm wget http://www.gtlib.gatech.edu/pub/centos/6.4/os/x86_64/Packages/yum-utils-1.1.30-14.el6.noarch.rpm rpm –root /yourroot/ –import RPM-GPG-KEY-CentOS-6 rpm –root /yourroot/ -e –nodeps redhat-release-server rpm –root /yourroot/ -e yum-rhn-plugin rhn-check rhnsd rhn-setup rhn-setup-gnome rpm –root /yourroot/ -Uvh –force *.rpm yum –installroot=/yourroot/ upgrade