Linux Basic Knowledge Four

1, the Replication/etc/skel directory is/home/tuser1, requires/home/tuser1 and its internal files belong to the group and other users do not have any access rights.

[Email protected] ~]# cp-a/etc/skel/home/tuser1/[[email protected] ~]# chmod-r go-rwx/home/tuser1/

2. Edit the/etc/group file and add the group Hadoop.

[Email protected] ~]# echo "hadoop:x:3007:" >>/etc/group

3. Manually edit the/etc/passwd file to add a new line, adding user Hadoop, whose basic group ID is the Hadoop group ID number; its home directory is/home/hadoop.

[[email protected] ~]# echo "Hadoop:x:3007:3007::/home/hadoop:/sbin/nologin" >>/etc/passwd[[email protected] ~] # ID hadoopuid=3007 (Hadoop) gid=3007 (Hadoop) groups=3007 (Hadoop)

4. Copy the/etc/skel directory as/home/hadoop, which requires that the genus Group and other users of the Hadoop directory be modified without any access rights.

[Email protected] ~]# cp-a/etc/skel/home/hadoop[[email protected] hadoop]# chmod-r Go-rwx/home/hadoop

5, modify the/home/hadoop directory and all the internal files of the owner of Hadoop, belong to Hadoop group.

[[email protected] hadoop]# chown -r hadoop: HADOOP /HOME/HADOOP[[EMAIL PROTECTED] HADOOP]# LS -ALTOTAL 16DRWX------.    3 hadoop hadoop   74 jun  8 22:35 .drwxr-xr-x. 15  ROOT   ROOT   4096 AUG 28 10:44&NBSP, .... -RW-------.   1 hadoop hadoop   18 nov 20  2015 . BASH_LOGOUT-RW-------.   1 hadoop hadoop  193 nov 20  2015  .BASH_PROFILE-RW-------.   1 hadoop hadoop  231 Nov 20   2015 .BASHRCDRWX------.   4 hadoop hadoop   37 Jun   8 22:34 .mozilla 

6 , displays the lines in the/proc/meminfo file that begin with uppercase or lowercase s, in two ways.

[[email protected] hadoop]# grep -i  ' ^s '  /proc/meminfo SwapCached:           204 kBSwapTotal:         511996 kBSwapFree:         496060  Kbshmem:              3732 kbslab:               76928 kbsreclaimable:       38064 kBSUnreclaim:         38864 kb[[email protected] hadoop]# grep   ' ^[ss]  /proc/meminfo  swapcached:          204 kbswaptotal:         511996 kBSwapFree:          496060 kbshmem:              3732 kbslab:               76928 kBSReclaimable:       38064 kbsunreclaim:        38864 kb

7. Displays the user whose default shell is non-/sbin/nologin in the/etc/passwd file.

[Email protected] hadoop]# CAT/ETC/PASSWD | Grep-v ":/sbin/nologin$" |cut-d:-F 1rootsyncshutdownhaltyanlibobobdistromandrivatest1mageiaslackwareopenstackuser1user2

8. Displays the user whose default shell is/bin/bash in the/etc/passwd file.

[Email protected] hadoop]# CAT/ETC/PASSWD | grep ":/bin/bash$" |cut-d:-F 1rootyanlibobobdistromandrivatest1mageiaslackwareopenstackuser1user2

9. Find one or two digits in the/etc/passwd file.

[Email protected] ~]# grep-op "\b\d{1,2}\b"/etc/ passwd0011223447506070812110121450999966658181595976323229297575424270708989747438387272

10. Displays the line (CENTOS6) that starts with at least one whitespace character in/boot/grub/grub.conf.

[Email protected] ~]# grgrep-p "^\s+"/boot/grub/grub.confroot (hd0,0) kernel/vmlinuz-2.6.32-642.el6.x86_64 ro root=/ Dev/mapper/vg_centos-lv_root nomodeset Rd_no_luks Lang=en_us.  UTF-8 rd_lvm_lv=vg_centos/lv_swap rd_no_md Sysfont=latarcyrheb-sun16 crashkernel=auto rd_LVM_LV=vg_centos/lv_root KEYBOARDTYPE=PC keytable=us rd_no_dm RHGB quietinitrd/initramfs-2.6.32-642.el6.x86_64.img

11. Display the/etc/rc.d/rc.sysinit file with # Beginning with at least one white space character followed by at least one non-whitespace character line (CentOS6).

[[email protected] ~]# grep -p  ' ^#\s+\s+ '  /etc/rc.d/rc.sysinit# /etc/rc.d/ rc.sysinit - run once at boot time# taken in part from  Miquel van smoorenburg ' S bcheckrc.# check selinux status# print a  text banner.# only read this once.# initialize hardware# set  default affinity# Load other user-defined modules# Load modules  (For backward compatibility with vars) # configure kernel parameters#  set the hostname.# sync waiting for storage.# device mapper &  related initialization# start any md raid arrays that haven ' t  been started yet# remount the root filesystem read-write.# clean  up selinux labels# if relabeling, relabel mount points.# mount all other  filesystems  (except for nfs and /proc, which is already# mounted) .  contrary to standard usage,# filesystems are not unmounted in  single user mode.# The  ' No '  applies to all listed  Filesystem types. see mount (8) .# check to see if a full  relabel is needed# update quotas if necessary# initialize  Pseudo-random number generator# configure machine if necessary.# clean  out /.# Do we need  (w|u) Tmpx files? we don ' T set them  up, but the sysadmin might...# clean up /var.# clean up  utmp/wtmp# clean up variouS /tmp bits# make ice directory# start up swapping.# set up  binfmt_misc# boot time profiles. yes, this should be somewhere  else.# Now that we have all of our basic modules  Loaded and the kernel going,# let ' s dump the syslog ring  somewhere so we can find it later# create the crash  indicator flag to warn on crashes, offer fsck with timeout#  Let rhgb know that we ' Re leaving rc.sysinit

1 2, the Netstat-tan command execution results in the "LISTEN", followed by or with a blank character end of the line.

[[email protected] ~]# netstat -tan | grep -p  "LISTEN\s*$" tcp         0      0 192.168.122.1:53         0.0.0.0:*                LISTEN     tcp         0      0 0.0.0.0:22               0.0.0.0:*                LISTEN     tcp         0      0 127.0.0.1:631            0.0.0.0:*                listen     tcp        0       0 127.0.0.1:25            0.0.0.0:*                LISTEN      tcp        0      0  127.0.0.1:6010          0.0.0.0:*                LISTEN      tcp6       0      0 :::22                    :::*                      LISTEN     tcp6       0      0 ::1:631                  :::*                      LISTEN     tcp6       0       0 ::1:6010                 :::*                      listen

13, add user bash, Testbash, basher, Nologin (this one user's shell is/sbin/nologin), and then find out the current system on its user name and the default shell of the same user information.

[[email protected] ~]# useradd bash[[email protected] ~]# useradd testbash[[email protected] ~]# useradd Basher[[email Pro Tected] ~]# useradd-s/sbin/nologin nologin[[email protected] ~]# grep-p "^ (\w+):. *\1$"/etc/passwdsync:x:5:0:sync:/sbi N:/bin/syncshutdown:x:6:0:shutdown:/sbin:/sbin/shutdownhalt:x:7:0:halt:/sbin:/sbin/haltbash:x:3008:3008::/home /bash:/bin/bashnologin:x:3011:3011::/home/nologin:/sbin/nologin

This article is from "Bo Zi in the Water" blog, declined to reprint!

Linux Basic Knowledge Four