We may want to add some swap space for a Linux box while only find that all disk space is partitioned and mounted. Some partition has large available free space. For such cases, we may not want to change the partition allocation. The solution may be to add a file based swap for Linux as…
before the packets ports (443) entering the firewall i would like to divert incoming packet of server (443) to input chain goes to FORWARD chain<br> so thats the incoming packets 100.43.xx.xx –sport 443 are send it to FORWARD instead of input chain<br> how to configure this in OUTPUT,FORWARD,POST AND PREROUTING CHAIN and this is my…
# ssh root@192.168.122.96 root@192.168.122.96’s password: Permission denied, please try again. Do according to [1]. NOTE: on Ubuntu, remember to restart ssh service like this “sudo restart ssh”. [1] https://access.redhat.com/documentation/en-us/red_hat_enterprise_linux/6/html/v2v_guide/preparation_before_the_p2v_migration-enable_root_login_over_ssh
If we want to check one program on one remote server, we need to know this server’s IP and port number. How to get this program’s port number in the remote server? # netstat -tulpn Remember to run this program with root permission since some programs can only be accessed by root.
Login without PWD is fast and efficient. Running commands in server from local machine also have these benefits. login without PWD: add PC A’s public key to PC B’s authorized keys. > a@A:~> cat .ssh/id_rsa.pub | ssh b@B ‘cat >> .ssh/authorized_keys’ > b@B’s password: Run command remotely ssh root@MachineB “ls” NOTE: running commands remotely is…
How to force a fsck of a file system, say the root, during the next rebooting of Linux? 2 possible ways: /forcefsck way for / # touch /forcefsck and reboot. Next time the / will be fsck’ed . systemd way Add these 2 kernel boot parameters: fsck.mode=force fsck.repair=yes What these 2 kernel parameters do: KERNEL…
How to disable the fastmirror yum plugin in CentOS 7 Linux? The fastestmirror function of yum is provided by the package `yum-plugin-fastestmirror`. However, because `yum` depends on it, the `yum-plugin-fastestmirror` package can not be removed. If you try to remove it, `yum` will report failures like. # yum remove yum-plugin-fastestmirror Loaded plugins: fastestmirror Resolving Dependencies…
Hello! Im trying to create a screen folder for the user apache, Not root. But it seems to fail, I have no idea on how to fix this issue. I only get the error: Cannot make directory ‘/var/run/screen/S-apache’: Permission denied Im using Cent OS 7 There may be various possible reasons. 2 common reasons: screen…
Question: how to find the disk where the Linux’s root(/) is on in Bash? The root may be on a LVM volume or on a raw disk. 2 cases: One example: # df -hT | grep /$ /dev/sda4 ext4 48G 32G 14G 71% / For another example: # df -hT | grep /$ /dev/mapper/fedora-root ext4…
On CentOS 7, using a normal user, encfs works just well. On CentOS 6, using the root user, encfs works. However, the problem is, on CentOS 6, using a normal user account, encfs does not work as on CentOS 7. $ encfs -s ~/t/.enc ~/t/enc EncFS Password: fuse: failed to exec fusermount: Permission denied fuse…
I tried to build a project while it reports: # ./autogen.sh Can’t exec “aclocal”: No such file or directory at /usr/share/autoconf/Autom4te/FileUtils.pm line 326. autoreconf: failed to run aclocal: No such file or directory How should I handle this? How to install aclocal? yum install aclocal shows: No package aclocal available. Error: Unable to find a…
For local filesystems, root usually has full access (read/write) to directories/files inside of it. But for NFS directory mounted from network, root usually has no permission to write to directories or files within the NFS directory. How to make root act similarly in an NFS directory to the behavior in local directories? The reason that…
I want to rename a user’s username on Linux. For example, rename user u1 to user1. How to change a user’s username on Linux? You can use the usermod command to modify the user’s info. For changing the user name, you can use the -l option: -l, –login NEW_LOGIN The name of the user will…
How to get the $PATH environment variables of another user in Bash on Linux? The current user running the Bash script is root. If the scripts is run by root, this piece of code will store the PATH from the environment of the user user1: user1path=$(su – $user1 -c env | grep ^PATH= | cut…
How to iterate all files and directories under a directory in Python? For example, I would like to iterate each file and directory under /mnt/data/ /mnt/data/ |– file.txt `– great That is: /mnt/data/files.txt /mnt/data/great You can use the os.walk to do this: root, dirs, files = os.walk(path).next() root will be the path.dirs will contain the…
How to enable SSH service on Fedora Linux? By default, it seems ssh is not enabled. Fedora may not have sshd service installed/enabled by default. You will need to install and configure it by yourself. The following instructions is for Fedora 22 as an example. First, install the sshd server by # dnf install openssh-server…
The good ssh-copy-id method which works well on common Linux seems not working for OpenWrt router. How to Passwordless SSH to an OpenWrt Router? OpenWrt’s SSH server is Dropbear. It can accept normal RSA keys. But the authorized_keys location is not the same as the openssh “~/.ssh/authorized_keys”. The location for the authorized_keys is /etc/dropbear/authorized_keys What…
I keep seeing messages in dmesg as follows with “exception Emask 0x10” -> “SError: { UnrecovData 10B8B BadCRC }” -> “failed command: READ FPDMA QUEUED” -> “hard resetting link”: [ 7395.936692] ata4.00: exception Emask 0x10 SAct 0xe000 SErr 0x280100 action 0x6 frozen [ 7395.936701] ata4.00: irq_stat 0x08000000, interface fatal error [ 7395.936703] ata4: SError: {…
I want to run screen on a remote host on which I do not have root/sudo privilege and screen is not installed. I can compile or copy the screen program that can run on the host. However, it reports: “Cannot make directory ‘/var/run/screen’: Permission denied” As screen is not installed on the host, the directory…
A try like the following command failed $ sudo echo “echo hello” > /usr/local/bin/hello with an message bash: /usr/local/bin/hello: Permission denied It seems the writing to the file is executed under the non-root user. How to redirect STDOUT of sudo command on Linux and write the content to the file (/usr/local/bin/hello here) as root? You…